The lymphocyte and macrophage profile in the pancreas and spleen of NOD mice: percentage of interleukin-2 and prolactin receptors on immunocompetent cell subsets.

The NOD mouse is a model for autoimmune diabetes that develops symptoms similar to Type I diabetes. The incidence of diabetes is greater in females but the degree of insulitis is comparable in both sexes. The purpose of this study was to assess the populations of lymphocytes and macrophages in the pancreas and spleen of NOD mice. Comparisons were made between male and female; young (32-40 days old) and old (197-297 days old); diabetic and non-diabetic mice. Using analytical fluorescent cell cytometry we quantitated the percentages of CD4, and CD8 T-cells, B-cells and macrophages and the percentages of these subsets expressing interleukin-2 (IL-2R), prolactin (PRLR) and Hi-intensity PRL (Hi-PRLR) receptors. Evaluation of T-splenocytes indicated a 2:1 ratio of CD4 to CD8 T-lymphocytes in the spleen. The pancreas had higher percentages of all of the subsets in the old male and female groups compared to their young counterparts. Pancreatic immunocompetent cell subsets expressed lower percentages of IL-2R, PRLR and Hi-PRLR compared to splenocytes. The results did not demonstrate any dramatic differences in the immunocompetent cell populations of the spleen or pancreas between male and female animals, however we were able to establish the percentage of immunocompetent cells with IL-2R, PRLR and Hi-PRLR as a reference for future studies.

Euprolactinemic Galactorrhea. Response of bioassayable prolactin to thyrotropin-releasing hormone.

OBJECTIVE: To define whether the pathophysiology of euprolactinemic galactorrhea (EuG) involves hyperresponsiveness to thyrotropin-releasing hormone (TRH). STUDY DESIGN: Basal and TRH-induced prolactin (PRL) patterns were examined in women with EuG (n = 7) and compared to those in controls (n = 10) with normal menstrual cycles. PRL activity was measured by radioimmunoassay (RIA) and Nb2 lymphoma cell bioassay (BA). The response of BA-PRL, RIA-PRL, the BA/RIA-PRL ratio and lactogenic activity to TRH given intravenously were studied. RESULTS: The response of RIA-PRL, BA-PRL, lactogenic activity (representing both PRL and growth hormone in the Nb2 lymphoma cell bioassay) and BA/RIA-PRL ratio were not significantly different in EuG as compared to controls. In both groups the combined BA/ RIA-PRL ratio increased at 15 (P = .006), 30 (P = .011), and 90 minutes (P = .022) after TRH injection as compared to zero time. The level of serum progesterone at the time of TRH stimulation did not affect the response of any parameter studied. CONCLUSION: The response of BA-PRL, RIA-PRL and the BA/RIA-PRL ratio to TRH was not significantly different in EuG as compared to controls. The mechanism of EuG did not involve hyperresponsiveness of BA-PRL, RIA-PRL, the BA/RIA-PRL ratio or lactogenic activity to TRH.

Influence of thyroxine and thyroxine with growth hormone and prolactin on splenocyte subsets and on the expression of interleukin-2 and prolactin receptors on splenocyte subsets of Snell dwarf mice.

A number of immune parameters were examined in Snell dwarf mice and compared with normal littermates. The number of splenocytes per gram of body weight were significantly decreased in dwarf animals, and the decrease was distributed throughout the CD4, CD8, B220, and MAC-1 subsets. The percentage of CD4 and CD8 splenocytes was markedly increased, and the percentage of B220 and MAC-1 splenocytes markedly decreased, in dwarf animals. In addition, the percentage of splenocyte T cells constitutively expressing interleukin-2 (IL-2) receptors and prolactin (PRL) receptors was decreased, with the CD4 subset presenting the most dramatic effect. The effects of replacing the hormones deficient in the Snell dwarf mouse (i.e., growth hormone [GH], prolactin [PRL], and thyroxine [T4] on the above immune parameters were also examined. The administration of T4 alone for 10 days corrected the defect in splenocyte cell numbers per grams body weight for both the CD4 and CD8 subsets, but only partially corrected the defect for the B220 and MAC-1 subsets. The addition of rbGH and rbPRL for the last 3 days of T4 injection had little additive effect on the number of CD4 and CD8 cells but increased the number of B220 and MAC-1 subsets to values comparable to those of normal animals on the basis of body weight. The decrease in the percentage of CD4 splenocytes in dwarf animals constitutively expressing IL-2R was partially corrected by T4 injection and completely corrected by the addition of rbGH and rbPRL for the last 3 days. The decrease in CD4 splenocytes constitutively expressing PRLR was partially corrected by T4 injection alone and the addition of rbGH and rPRL resulted in percentages comparable to that of normal animals. The results indicate that Snell dwarf animals are deficient in immune parameters and that the administration of the hormones lacking in this animal can correct the deficiencies.

The influence of thyroxine, growth hormone and prolactin alone and in combination on the production of prolactin-like activity by splenocytes from Snell dwarf mice.

The production of a prolactin (PRL)-like substance by mitogen-stimulated immunocompetent cells has been reported previously for a number of species. The Snell dwarf mouse has a deficiency in thyrotropin (TSH), growth hormone (GH) and prolactin (PRL) as a result of a defect in the pituitary Pit-1 promoter. Since the gene for PRL is present in the dwarf mouse pituitary but not activated it was of interest to determine whether a similar deficiency existed for splenocytes from the dwarf animal. Irradiated splenocytes from dwarfs and normal littermates were cocultured in synthetic AIM-V medium with Nb2 cells and stimulated with concanavalvin A (Con-A). The 3H thymidine incorporation into Nb2 cells in cocultures was quantitated by the addition of mouse PRL to Nb2 cells alone. Splenocytes from dwarf mice produced significantly less PRL-like activity (p < 0.02) than did splenocytes from normal animals. The administration of thyroxine (T4) to dwarf mice increased body weight (BW) gain and the number of splenocytes/g BW. The administration of recombinant bovine GH but not recombinant bPRL further increased body weight gain over T4 alone but neither pituitary hormone had any additional effect on the number of splenocytes/g BW over that noted for T4 alone. Prolactin and GH alone had no effect on splenocyte numbers/g BW. The decreased production of PRL-like activity in the dwarf mouse was not altered by either GH or PRL injection. The injection of T4 alone and in combination with pituitary hormones increased the production of PRL-like activity by dwarf splenocytes to values similar to that observed for normal animals.

Evaluation of prolactin-like activity produced by concanavalin-A stimulated mouse splenocytes.

The prolactin (PRL)-like activity released into synthetic culture medium from concanavalin-A (Con-A)-stimulated mouse splenocytes was bioassayed using 3H thymidine incorporation into Nb2 lymphoma cells. At low cell density (1.0 x 10(6) cells/ml medium) Con-A-stimulated splenocytes from Balb/c mice released more PRL-like activity than did splenocytes from normal C3H/HeJ mice. This difference was maintained with animals of either sex, and for animals of different ages (1, 3 and 5 months). The strain difference was observed both when splenocytes were co-cultured with Nb2 cells, and when postcultured medium from splenocytes was tested. Con-A-stimulated splenocytes also released a substance into the medium which was inhibitory to PRL-induced Nb2 cell proliferation. The concentration of the inhibitory substance in the medium was related to the number of splenocytes in culture and was similar in splenocyte media preparations from both strains of mice. Polyclonal antisera to bovine PRL, rat PRL, mouse placental lactogen II, and mouse PRL did not neutralize the effect of Con-A-stimulated splenocytes to induce Nb2 cell proliferation. Bioassay of the partially purified PRL-like activity found in postcultured medium indicated that the dose-dependent induction of Nb2 cell proliferation was parallel with that of purified mPRL. Using two mouse PRL antisera (Sinha and Talamantes #118) in Western blot analyses, no antibody binding was observed to the partially-purified splenocyte PRL-like material. The data from the antisera neutralization experiments and the SDS/PAGE Western blot analyses clearly indicated that the PRL-like activity produced by Con-A-stimulated splenocytes has little homology with pituitary PRL. Further studies are required to establish the precise molecular identity of the PRL-like activity from Con-A-stimulated splenocytes.

Evidence for the release of a prolactin-like substance by mouse lymphocytes and macrophages.

The influence of co-cultures of irradiated mouse thymocytes, splenocytes, and mesenteric lymph node cells on the proliferation of Nb2 cells in synthetic medium were studied. Irradiated thymocytes with or without the addition of ovine prolactin (oPRL) decreased the incorporation of 3H-thymidine into Nb2 cells. Irradiated splenocytes and lymph node cells when co-cultured with Nb2 cells and stimulated with concanavalin A (Con-A) induced Nb2 cell proliferation. Lipopolysaccharide stimulation of irradiated splenocytes and lymph node cells, however, did not alter Nb2 cell proliferation. Isolated thioglycolate-induced peritoneal macrophages stimulated Nb2 cells to incorporate 3H-thymidine while IFN-gamma-stimulated macrophages decreased PRL-induced Nb2 cell proliferation when isolated 48 but not 24 hr before co-culture. The addition of a mouse PRL antiserum to macrophage/Nb2 cell co-cultures did not alter the proliferative activity induced by macrophages. The preliminary data presented indicate that Con-A-stimulated, irradiated splenocytes and lymph node cells, and isolated peritoneal macrophages secrete a PRL-like activity. The PRL-like activity of macrophages, however, does not appear to be of mouse origin, and it is suggested that macrophages, which have surface PRL receptors, sequestered PRL from the fetal calf serum in the medium used to isolate them and release this PRL when co-cultured.

Prolactin modulates the incidence of diabetes in male and female NOD mice.

The nonobese diabetic (NOD) mouse develops diabetes spontaneously due to autoimmune destruction of the pancreatic islets with a higher incidence in the female than the male. Prolactin (PRL), a hormone whose role has been previously focused on reproduction and lactation has been demonstrated to influence immune responses. In this study, we investigated the effect of hypoprolactinemia and hyperprolactinemia on the incidence of diabetes in male and female NOD mice. Our hypoprolactinemia model was induced from the time of weaning (21 days of age) to 112 days of age by daily injections of 200 micrograms of bromocriptine (CB-154). A hyperprolactinemic model was induced by a syngeneic anterior pituitary transplant (APT) to the kidney capsule at 35 days of age and maintained until 112 days of age. Additional experimental groups were also investigated. A group of males received pituitary transplants combined with daily subcutaneous injections of CB-154. A group of females treated with CB-154 was also given daily subcutaneous injections of 30 micrograms of oPRL. An ovariectomized (OVX-Control) group of females was also established to serve as a second control for the OVX-APT group. Bromocriptine administration did not significantly decrease plasma PRL levels compared to controls (CTRL) while APT animals had plasma PRL levels that were significantly higher (P < 0.01) than those of CTRL and CB-154 animals. These differences were observed in animals of both sexes. Bromocriptine treatment of APT groups significantly lowered plasma PRL levels from their respective controls. Plasma PRL from the OVX-Control group was markedly lower than the intact female control. The incidence of diabetes was significantly lower in female mice receiving CB-154 injections compared to the intact female CTRL group at 84, 98 and 112 days of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of prolactin and growth hormone on the activation of dwarf mouse lymphocytes in vivo.

The influence of recombinant bovine prolactin (PRL) and recombinant bovine growth hormone (GH) was examined on the popliteal lymph node (PLN) expression of interleukin-2 receptors (IL-2R) in female Snell dwarf mice and normal litter mates after concanavalin A footpad injection. The absolute number of PLN CD4+, CD8+, or B+ cells of dwarf mice was less than that observed for normal litter mates, but when adjusted for the difference in body weight, only the absolute number of B cells was lower in dwarf animals when compared with normal litter mates. The injection of PRL or GH did not alter the observation. The administration of recombinant bovine PRL to normal animals, but not recombinant bovine GH, increased the expression of IL-2R or unstimulated PLN CD4+ and CD8+ subsets. Hormone administration to dwarf animals, however, did not alter the expression of IL-2R on unstimulated PLN T cell subsets. PLN cells from dwarf animals were poorly activated in vivo after injection of concanavalin A and the level of IL-2R expression induced was only 50% of that seen in the PLN of normal animals. The administration of PRL and GH completely corrected the defective induction of IL-2R expression on PLN from dwarf animals after concanavalin A stimulation. These findings strongly suggest that PRL and/or GH play an important role at some stage of the T cell activation process in vivo. Further studies are needed to precisely identify the defect in the dwarf mice.

Identification by analytical flow cytometry of prolactin receptors on immunocompetent cell populations in the mouse.

Five monoclonal antibodies (T1, T6, U5, U6, and E21) made to the external portion of the rat PRL receptor (PRL-R) were conjugated to fluorescein isothyrocynate and used to examine the presence of PRL-R on mouse lymphocytes and macrophages using analytical flow cytometry. The monoclonals were initially evaluated using Nb2 cells, a cloned line from a rat lymphoma, and NOG-8 cells, a cloned line from normal mouse mammary gland tissue, which are known to have PRL-R. All monoclonal antibodies bound to these cells, but the U5 monoclonal gave the best separation from unstained cells. CTLL-2 cells, a mouse lymphoma cell line containing interleukin-2 receptors, did not bind to any of the monoclonals. Isolated thioglycolate-induced peritoneal macrophages contained PRL-R, and the PRL-R monoclonal U5 gave the best separation from unstained cells. Eighty-five percent of macrophages constitutively had PRL-R using this monoclonal. In vivo stimulation of the popliteal lymph node by the injection of Concanavalin-A (Con-A) into the right foot pad of intact and ovariectomized (OVX) BALB/c mice induced, at the end of 10-12 h, a marked increase in interleukin-2 receptor (IL-2R) expression on CD4, CD8, and B-cells compared to the unstimulated left popliteal lymph node. The number of CD4 and CD8 cells from OVX animals with IL-2R was twice that from intact animals, whereas no difference in the percentage of B-cells with IL-2R was evident. PRL-R were constitutively expressed on 5% of the CD4 cells and 20% of the CD8 cells and were increased in the Con-A-stimulated lymph node when examined with the U5 PRL-R monoclonal. A higher percentage of CD4 and CD8 cells from OVX animals constitutively expressed PRL-R, and when stimulated with Con-A, a further increase was observed compared to the level in intact animals. Using the U5 monoclonal, over 80% of the B220 cells constitutively expressed PRL-R; however, when T1, T6, and U6 monoclonals were examined, the percentage was considerably below (20%) than that observed for U5. Con-A stimulation did not alter the percentage of B220 cells expressing PRL-R. These results show the importance of identifying lymphocyte subsets and examining a number of PRL-R monoclonals in determining lymphocyte PRL-R expression on the surface of the cell.

The effect of neonatal sex hormone manipulation on the incidence of diabetes in nonobese diabetic mice.

The nonobese diabetic (NOD) mouse is a model of Type I (insulin-dependent) diabetes. It develops autoimmune pancreatic beta-cell lesions characterized by lymphocytic infiltration and beta-cell destruction. The incidences of diabetes for male and female NOD mice in our colony were 24% and 73%, respectively. In this study, we investigated the effect of neonatal manipulation of the sex hormone profile on the incidence of diabetes in male and female NOD mice. One day after birth, male mice were castrated and female mice were either ovariectomized, given testosterone, or ovariectomized and given testosterone. The mice were maintained for 140 days and blood samples were collected biweekly starting at 42 days old. Diabetes was determined by three consecutive blood glucose levels > 200 mg/dl. Neonatal gonadectomy increased the incidence of diabetes in males but decreased it in females. Females treated with testosterone also had a decreased incidence of diabetes, whereas ovariectomy plus testosterone increased the incidence to 100%. Castration decreased the body weight in males and increased body weight in females. Testosterone treatment with or without ovariectomy also increased body weight. From these studies, we concluded that neonatal hormonal imprinting has a significant influence on the incidence of diabetes in the NOD mouse.

Influence of bromocriptine administration to mothers on the development of pup thymocyte and splenocyte subsets and on mitogen-induced proliferation in the mouse.

The influence of prolactin (PRL) on the development of the immune system in the mouse was studied by injecting mothers with bromocriptine (CB-154) to produce hypoprolactinemic milk. Alterations in pup thymocyte and splenocyte cell subsets were observed to graded doses of CB-154 administered to mothers. There was an increase in the relative percentages of neonate thymic CD4 and CD8 cells at 5 days of age when mothers were injected with 100 micrograms of CB-154 2 x daily from day 1 to 5 of lactation, however, there was no alteration in absolute thymic subset cell numbers. The relative percentage of pup spleen CD4, CD8 and B cells were increased when mothers were administered 50 or 100 micrograms of CB-154 and the 50 micrograms dose resulted in a significant increase in the absolute number of CD4 cells while the 100 micrograms dose induced a significant decrease in the three splenic cell subsets examined. Graded doses of CB-154 administered to mothers resulted in decreases in the PRL concentration of stomach milk as measured by the Nb2 cell proliferation assay. The serum PRL level of the pups, however, was not altered by any dose of CB-154 injected to the mothers. The administration of PRL to pups nursing mothers given the 100 micrograms dose of CB-154 did not alter the pup thymocyte and splenocyte subset population from that of litter-mate controls. The administration of mouse PRL and mouse growth hormone antisera to pups nursing saline-injected mothers did not alter thymocyte and splenocyte subsets from that of saline-injected litter mate controls. The proliferation of neonatal thymocytes by Con-A stimulation was not altered by CB-154 injection to mothers and PRL administration to pups. However, since the percentage of thymic CD4 and CD8 cells in the thymus was increased 2 to 3 fold, the apparent lack of effect was in fact a decrease in the responsiveness of the thymocytes. Con-A stimulation of neonatal splenocytes resulted in a significant increase in proliferation for mothers administered CB-154 in keeping with the increase relative percentage of CD4 and CD8 cells observed. Prolactin administration to the pups did not alter the response. LPS stimulation of neonatal splenocytes increased the proliferation of B cells taken from pup nursing mothers administered CB-154 and PRL administration appeared to partially block this proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

Prolactin size heterogeneity in human follicular fluid: a preliminary study.

Follicular fluid from mature preovulatory follicles was examined for the presence of prolactin (PRL) heterogeneity. Two pools of follicular fluid aspirates were used: one from follicles in which the ova were successfully fertilized in vitro and the other from follicles in which the ova were not successfully fertilized. Follicular fluid aspirates were concentrated by ultrafiltration and subjected to Sephadex G-100 gel chromatography. Fractions were assayed for immunoactive PRL by radioimmunoassay (RIA-PRL) and for bioactive PRL by the Nb2 lymphoma cell bioassay (BA-PRL). The major portion of RIA-PRL activity appeared as a low-molecular-weight component and accounted for 88% of the total PRL activity in the fertilized group and 87% in the unfertilized group. A high-molecular-weight component was also evident (12% and 13% for the two groups, respectively). The high-molecular-weight component in both groups was not active as PRL in the bioassay. These results demonstrate that while two immunoactive, heterogeneous forms of PRL exist in human follicular fluid when measured by RIA, it is only the low-molecular-weight form of PRL that is biologically active as established by Nb2 lymphoma cell bioassay.

Prolactin and growth hormone in the regulation of the immune system.

Evidence implicating prolactin (PRL) and growth hormone (GH) in the regulation of the immune system has been reviewed. Hypophysectomized animals have deficiencies in both cell-mediated and humoral immunological functions and either PRL or GH corrects these deficiencies. Animals administered bromocryptine, a drug that specifically blocks PRL release, have impaired immune responses similar to hypophysectomized animals, and again both PRL and GH correct these deficiencies. Genetically dwarf animals, which lack both PRL and GH, are also immunocompromised, and once again PRL and GH can correct the deficiencies. In dwarf animals, however, fewer studies have examined PRL actions. In growth-deficient children, immune function is not dramatically altered and basal secretion of GH has been reported. Very few clinical studies have examined whether PRL secretion is also deficient, and this may explain why a clear loss in immune function is not evident in growth-deficient children. In a number of species, including man, both PRL and GH stimulate thymic function and increase the secretion of thymulin, a thymic hormone. No studies, however, have reported on the effects of PRL and GH on other thymic hormones. A number of studies have reported in vitro effects of PRL and GH on cells involved with immunity, and the presence of high-affinity PRL and GH receptors have been observed on a number of these cells. The action of GH on the proliferative response of cells involved with immunity in vitro appears to be mediated by the production of insulin-like growth factor I. The effect of PRL on insulin-like growth factor I production by these cells has not been examined. One of the most consistent findings from in vitro studies is that prolactin antisera blocked a number of immune reactions. This led to the discovery that cells involved with immunity appear capable of producing PRL and GH, but the physiological significance of these observations have not been explored. There is a great need to identify the cell types responding to PRL and GH and this should be a goal of future investigations. There is also a need for investigators to be aware that both PRL and GH are involved in the regulation of the immune system and to design experiments to elucidate where each functions in the maturation cascade of cells involved with immunity. From the evidence available, it is apparent that PRL and GH have an important function in the immune system and future investigations should be directed toward elucidating their site(s) of action.

Macroorchidism and testicular fibrosis associated with autoimmune thyroiditis.

A 16-year-old male with long-standing atrophic chronic lymphocytic thyroiditis was evaluated for macroorchidism. A testicular biopsy prior to treatment revealed peritubular and interstitial fibrosis, reduced spermatogenesis and sparse Leydig cells with nonprominent smooth endoplasmic reticulum. Biological/immunological LH and FSH ratios were reduced, I-LH and FSH response to GnRH was blunted, and levels of testosterone and androstenedione were low. Twenty-two months after thyroid treatment, the testicular size was unchanged, and the degree of fibrosis showed minimal regression. Spermatogenesis with normal morphology was present, Leydig cells with Reinke crystals were present, and surface area and diameter of the seminiferous tubules had increased only slightly. There was a normal I-LH and FSH response to GnRH, and normal levels of testosterone and androstenedione. This study, along with previous reports, suggests that the etiology of the hypothyroid state may influence the development of testicular fibrosis.

The effect of transient dopamine antagonism on thyrotropin-releasing hormone-induced prolactin release in female rats during the estrous cycle.

Prolactin (PRL) release induced by TRH was examined on each day of the estrous cycle in female rats in which pituitary dopamine (DA) receptors were blocked pharmacologically. The objective was to determine if an interaction exists between hypothalamic inhibitory and releasing hormones with regard to prolactin (PRL) secretion. Domperidone (0.01 mg/rat i.v.) followed 5 minutes later by the administration of the DA agonist 2-Br-alpha-ergocryptine maleate (CB-154, 0.5 mg/rat i.v.) were used to produce a transient (less than 1 hr) dopamine blockade. One hour later, thyrotropin-releasing hormone (TRH, 1.0 microgram/rat i.v.) was given to stimulate PRL release. On the morning of proestrus, TRH released a significantly greater quantity of PRL into the plasma after DA antagonism compared to control animals which did not receive the dopamine antagonist. Dopamine antagonism also enhanced the effectiveness of TRH on the mornings of estrus and metestrus. The response on estrus was significantly greater than the response on proestrus. However by the morning of diestrus, TRH-"releasable" PRL was greatly diminished. Our results suggest that DA antagonism is able to shift differing quantities of PRL into a TRH "releasable" pool on several days of the estrous cycle and that the control of this mechanism is acute.

A relationship between neonatal breast size and cord blood testosterone level.

The present study was performed to determine if any hormone measured in cord blood correlates with the size of the neonatal breast or the presence of galactorrhea. A total of 144 term newborn infants were examined. Estradiol (E2), progesterone (P), testosterone (T), and thyrotropin (TSH) were determined by radioimmunoassay (RIA), and prolactin (PRL) was determined by both RIA and biological activity (BA). The female breast (8.5 +/- 2.0 mm) was found to be larger than that of the male (7.8 +/- 2.1 mm, p less than 0.05). The only hormonal difference between sexes was a higher T level in the male infants (8.0 +/- 3.0 nmol per L vs. 5.5 +/- 1.9 nmol per L, p = 0.002). None of the other hormones measured by RIA correlated with the size of the neonatal breast or the presence of galactorrhea. The BA of PRL was widely variable compared to the PRL RIA but also failed to correlate with neonatal breast size or galactorrhea. This study suggests that T might be one factor in determining the size of the neonatal breast.

Stress-induced suppression of the prolactin afternoon surge in ovariectomized, estrogen-treated rats and the nocturnal surge in pseudopregnant rats are accompanied by an increase in median eminence dihydroxyphenylacetic acid concentrations.

Experiments were performed to determine whether the suppression of prolactin (PRL) surges during restraint was accompanied by changes in the activity of tuberoinfundibular dopamine (TIDA) neurons in the median eminence. Animals were either ovariectomized and estrogen-treated (OVX-PEP) or cervically stimulated to induce pseudopregnancy (PSP). Restraint stress was administered by tying the hind legs together with plastic-coated bell wire. Animals were decapitated following 15 or 30 min of restraint stress or immediately after removal from the animal room (control) when PRL levels were basal (10.00 h), at the peak of the afternoon PRL surge in OVX-PEP animals (17.00 h) or the nocturnal PRL surge in PSP animals (05.00 h). Median eminence dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) were significantly decreased in control rats at 17.00 h when compared to control rats at 10.00 h (103.1 +/- 3.7 vs. 85.8 +/- 3.3 and 11.4 vs. 7.1 +/- 0.4 pg/micrograms protein, respectively) and plasma PRL was markedly elevated. Restraint stress at 10.00 h resulted in a significant increase in serum PRL, but this increase was not accompanied by a change in DA or DOPAC when compared to control animals (103.1 +/- 3.7 vs. 107.9 +/- 4.8 and 11.4 +/- 0.4 vs. 10.4 +/- 0.6 pg/micrograms protein, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

The physiology and mechanisms of the stress-induced changes in prolactin secretion in the rat.

It is well known that stress in a number of forms induces the secretion of prolactin (PRL) in a number of species. What is not well known is that under certain conditions stress will also induce a decrease in PRL secretion. The conditions whereby stress decreases PRL are those where PRL secretion is elevated such as during the proestrous afternoon surge and during the nocturnal surge of pseudopregnancy. The physiologic significance of the stress-induced increase of PRL is suggested to be important in maintaining the competence of the immune system. The significance of the stress-induced decrease of PRL does not appear to have a major consequence on the physiology of reproduction in the rat and it is suggested that future studies be directed towards its significance in the immune system. The literature is reviewed dealing with the regulation of PRL secretion with emphasis on the factors that generate PRL surges in the rat. In addition the mechanism(s) of the stress-induced increase and decrease is (are) also examined. A hypothesis is presented suggesting an interaction between tuberoinfundibular dopamine secretion and a hypothalamic prolactin releasing factor in the generation of PRL surges and the differential effects of stress on PRL secretion.

Serum interleukin 2 (IL-2) levels and prolactin bioactive/radioimmunoassay ratios of women at risk for breast cancer.

In a cohort of women at high risk for developing breast cancer we have observed that 74% of the women with prolactin BA/RIA ratios over 1.4 had detectable levels of IL-2 in their serum (990 +/- 400 mU/ml) and the IL-2 levels were correlated with the prolactin BA/RIA ratio (R = 0.79; P greater than 0.004). Women with BA/RIA ratios were either approximately 1.0 or less than 0.55 had lower levels of serum IL-2 (177 +/- 70 and 130 +/- 40 mU/ml, respectively). Detectable levels of serum IL-2 were found in 58% of those women with BA/RIA ratios of 1.0 and 55% of those with BA/RIA ratios less than 0.55.

The restraint stress-induced decrease of the nocturnal prolactin surge and the physiology of pseudopregnancy and pregnancy in the rat.

Experiments were performed to determine whether the restraint stress-induced decrease of the nocturnal prolactin (PRL) surge affected the length of pseudopregnancy (PSP) and/or the outcome of pregnancy in rats. Vaginal cycles were monitored daily and animals were electro-mechanically cervically stimulated on the morning of metestrus to induce PSP. Animals were restraint stressed by tying the hind legs together with plastic coated bell wire beginning on day 1 of PSP from 0100-0700h with reapplication of stress at 0400h for 6-9 days and then blood sampled for PRL and progesterone plasma levels. Restraint stress significantly decreased plasma PRL (P less than 0.001) and progesterone (P less than 0.05) levels. The length of PSP was significantly decreased (P less than 0.01) for restraint animals and for control animals that were blood sampled compared to control animals that were not sampled. In the pregnancy experiment, animals were mated upon arrival into the laboratory and assigned to one of four groups. For the restraint group, stress was initiated on day 1 of pregnancy as indicated by the presence of sperm in the vaginal lavage. Animals were stressed for 6-9 days for 6 hours during the nocturnal PRL surge as described above. One control group had no treatment; a second control group was sampled only, and a third control group was injected daily with pimozide, a dopamine antagonist, and stressed for 6-9 days. The group which received no treatment had significantly greater (P less than 0.05) incidence of successful pregnancy compared to the other 3 groups; there were no differences (P greater than 0.05) between the sampled, restraint and restraint + pimozide groups in the incidence of successful pregnancy. We conclude that restraint stress during the nocturnal PRL surge minimally affects the length of PSP and that the effect of stress on the outcome of pregnancy is not due to the decrease in nocturnal PRL surge.