Seroprevalence of Toxoplasma gondii antibodies amongst pregnant women at the Lagos State University Teaching Hospital, Nigeria.

BACKGROUND: Toxoplasma gondii (T.gondii), an obligate intracellular parasite found in many species throughout the world, causes a variety of clinical syndromes in humans and animals. It is also associated with morbidity and mortality in pregnancy. Hence the need to determine the seroprevalence of antibody to toxoplasmosis gondii amongst pregnant women. SUBJECTS AND METHODS: A cross- sectional study was carried out using patients attending the ante-natal clinic of Lagos State University Teaching Hospital Ikeja. All consenting newly registered ante-natal patients were recruited consecutively into the study within a time frame of six weeks during which a total of 179 pregnant participants were recruited. Literate participants filled self administered questionnaires whilst the non-literate participants were interviewed by research assistants. Five milliliters of blood was collected from each participant after obtaining patient's consent. Sera were assayed for antitoxoplasmosis IgG antibody by enzyme linked immunosorbent assay. (ELISA.) RESULTS: A total of 179 pregnant women were studied. Almost 50.8% were between the ages of 25-30 years, 70.8% of the patients studied, had tertiary education. An assessment of the patients' status to anti-toxoplasmosis IgG showed 40.8% were positive while 59.2% were negative. Pet-keeping was a practice amongst only 6.1% of patients whilst 90.5% did not keep pets. Out of those who kept pets, 63.6% were positive while 39.5% were negative. Amongst those who did not keep pets, 39.5% were positive while 60.5% were negative. This difference was not statistically significant. (P=0.261) CONCLUSION: It appears that seroprevalence of toxoplasmosis IgG antibody amongst the pregnant women in this study population is high. Therefore, it is valuable to follow up the IgMantibody status of their off springs as its presence indicates recent exposure.

Seroprevalence of HIV among male prisoners in Lagos State, Nigeria.

OBJECTIVE: To determine the seroprevalence of HIV I & II antibodies among prisoners in Lagos State. PATIENTS & METHODS: A total of 300 male prisoners from Kirikiri Maximum and Medium security prisons and Ikoyi prisons had their blood samples screened for antibodies against human immunodeficiency virus (HIV) types I & II by ELISA-based technique using immunocomb II HIV I & II Bispot kits. Samples that were positive were confirmed by another ELISA-based technique using immunocomb I & II combifirm kits. RESULTS: The seroprevalence of HIV antibodies was 6.7, which translated to 20 of the 300 prisoners screened. Only one (0.3) of the prisoners had HIV II infection, the rest being due to HIV I. There was no prisoner with concomitant HIV I & II infection. The age groups 20-29 and 30-39 were most affected. CONCLUSION: The finding of 6.7 as prevalence in this study, which is slightly higher than the national prevalence in the year 2000 confirms that there may be activities in the prisons that increase the risk of acquiring HIV infection.

Principles of blood transfusion service audit.

Blood transfusion is still an important procedure in modern medical practice despite efforts to avoid it. This is due to it's association with infections especially HIV. It is therefore necessary to have proper quality control of its production, storage and usage [1]. A way of controlling usage is to do regular clinical audit. To effect this, there has to be an agreed standard for appropriate use of blood. The aim of this paper is to briefly highlight the importance of audit, audit procedures and tools i.e. required records, development of audit criteria and audit parameters. Every hospital/blood transfusion center is expected to develop a system of audit that is appropriate to its needs. The suggestions are mainly based on the experience at the Lagos University Teaching Hospital and the Lagos State Blood Transfusion Service.

Bilateral tubal pregnancy. A report of an unusual case.

BACKGROUND: Bilateral tubal pregnancies are rare and are usually confirmed simultaneously during the same operation. We report a case in which the right salpingectomy was performed seven weeks before the left salpingectomy. When the right salpingectomy was done, the left uterine tube appeared entirely normal. CASE: A 38-year-old woman underwent laparoscopic surgery for suspected right tubal pregnancy. A right tubal pregnancy was found to have partially aborted into the peritoneal cavity. The left uterine tube was carefully inspected and appeared normal. Histopathology of the right tube showed products of conception and chorionic tissue. Seven weeks after surgery, the woman presented in hemorrhagic shock necessitating emergency laparotomy and left salpingectomy. Histopathology of the left tube confirmed the presence of chronic tissue. The patient did not have coitus between the two salpingectomies. CONCLUSION: The explanation of the presentation is uncertain. However, this case underscores the importance of careful follow-up of patients after laparoscopic surgery for ectopic pregnancies.

Chloroquine-induced retardation of foetal lung maturation in rats.

Chloroquine (CQ) is a widely used drug and its administration has been reported to increase surfactant- associated phospholipids in lungs. We have used histomorphometric techniques to study the effects of CQ on foetal lung maturation in rats. CQ (40mg/kg BW) or saline was administered to pregnant rats on days 20 and 21 of gestation. A third group received the same dose of CQ on days 20 and 21, and in addition, hydrocortisone (HD; 25 mg/kg BW) on day 21 of pregnancy. Foetuses were delivered by hysterotomy on day 22. The lungs were weighed, fixed in Bouin's fixative and embedded in paraffin. Morphometric studies were performed on 5 microns-thick sections. The lung weight/100g BW, the volume density of lung saccular spaces, and the cross-sectional area and volume of the saccular spaces were reduced but the numerical density of the saccules was not decreased in foetuses exposed to CQ. With the exception of lung weights, which were lower in the foetuses exposed to CQ and HD, there were no other differences between this group and that exposed to CQ only. The results suggest that CQ attenuates the expansion of saccular spaces which occurs in preparation for post-natal gaseous exchange, and thus CQ retards foetal lung maturation. Although HD further reduced lung weights as expected from its reported action on foetal lungs, it did not reverse the CQ-induced retardation in lung maturation.

Morphometric analysis of the effect of chloroquine on rat foetal lung maturation.

Pregnant Sprague-Dawley rats were injected with chloroquine phosphate (40mg/kg b. wt 1.p) in the late canalicular (day 20) and early terminal-sac (day 21) and sacrificed in the late terminal sac (day 22 = term) stage of foetal lung development. The control animal received normal saline. Morphometric evaluation of the lungs by light microscopy revealed three important exposure-related lesions. They were: (a) reduction in the volume density of parenchyma and saccular space, (b) reduction in the volume of an average saccule and, (c) an increase in the number of saccules per unit volume (Numerical Density). The observations suggest that chloroquine retards foetal lung maturation by reducing the saccular expansion which takes place immediately preterm. However, the possible practical implications are unclear.

The extracellular matrix components laminin, fibronectin, and collagen IV are present among the epithelial cells forming Rathke's pouch.

Cell-matrix interactions probably play a cooperative role with cell-hormone interactions to ensure normal differentiation of the adenohypophysis. The extracellular matrix (ECM) surrounding adult adenohypophysial cells contains laminin but its embryonic development has not been described. This study was carried out to test the hypothesis that adenohypophysial cells are associated with components in the ECM prior to cellular differentiation in the adenohypophysis. Fetuses were removed from Golden Syrian hamsters every 12 h from embryonic days 8.5-14. Coronal and sagittal 5-microns-thick sections of paraplast-embedded embryos were stained for fibronectin, laminin, or collagen IV using avidin-biotin immunoperoxidase staining. The adenohypophysial anlage was observed initially as a group of epithelial cells (Rathke's pouch) in the roof of the stomatodeum in contact with a basement membrane. The basement membrane stained positively for laminin, collagen IV and fibronectin. Lighter staining for laminin, fibronectin and collagen IV was observed between the developing adenohypophysial cells in Rathke's pouch. Proliferative activity was apparent in the antero-inferior region of Rathke's pouch and resulted in the formation of the bulk of the adenohypophysis. Mesenchyme infiltrates the region between the base of Rathke's pouch and the oral epithelium, thus separating the two. The basement membrane surrounding the pouch appears to become discontinuous in the regions of high proliferative activity. These results show that ECM components appear early during the development of adenohypophysial cells prior to their cellular differentiation into hormone-containing cells. This association between ECM components and developing adenohypophysial cells provides the anatomical basis for cell-ECM interactions to influence adenohypophysial development and differentiation.

Reconstituted basement membrane influences prolactin, LH, and FSH secretion from adult and fetal adenohypophyseal cells in vitro.

These investigations tested the hypothesis that secretion of prolactin (PRL), LH, and FSH in vitro is influenced by the substratum on which adult or fetal adenohypophyseal cells are cultured. Adenohypophyses were removed from adult male Golden Syrian hamsters and from fetal hamsters on day 16 of gestation. The glands were dissociated and cultured in a 1:1 mixture of Dulbecco's Modified Eagle's Medium (DMEM) and Ham's F-12 medium containing 10% fetal bovine serum (FBS), 25 mM Hepes, and antibiotics. The cells were cultured on three substrata: glass, laminin, and the reconstituted basement membrane of the Engelbreth-Holm-Swarm (EHS) tumor (Matrigel). Medium was collected and replaced every 48 h for 14-22 days. Concentrations of PRL, LH, and FSH in medium were measured by RIA. The substratum influenced hormone secretion. PRL concentrations were elevated in cultures of adult cells on Matrigel in each of four experiments. Adenohypophyseal cells on Matrigel maintained a rounded shape longer than cells on glass or laminin. In studies using fetal adenohypophyseal cells, PRL concentrations were elevated significantly in medium from cultures on Matrigel at and after 2 days as were concentrations of LH and FSH after 6 days. Additional experiments showed that the higher PRL concentrations in medium surrounding adult cells plated on Matrigel were not due to the release of soluble factors from Matrigel, differential cell attachment on Matrigel, the differential presence of adenohypophyseal fibroblasts, nor differential rates of cell proliferation. The results show that Matrigel maintains the secretion of PRL from adult adenohypophyseal cells in vitro more effectively than glass or laminin substrata and support the hypothesis that cell-matrix interactions mediate the observed differences. The results also show that in long-term cultures (14-22 days), fetal adenohypophyseal cells secrete significantly more PRL, LH, and FSH on Matrigel than they secrete when cultured on glass or laminin. Thus, Matrigel influences the function and possibly the maturation of adenohypophyseal cells in vitro. Furthermore, although laminin is the most abundant component in Matrigel, the effects of Matrigel on lactotrophs and gonadotrophs in vitro are probably not attributable solely to its laminin content.

Intraperitoneal injection of chloral hydrate causes intra-abdominal adhesions and unilateral testicular atrophy in golden Syrian hamsters.

We investigated the reason for the high mortality we had observed in hypophysectomized-orchidectomized Golden Syrian hamsters that were anesthetized with intraperitoneal (i.p.) injections of chloral hydrate (CH). Intact male Golden Syrian hamsters were injected intraperitoneally with 0.1cc/100g BW of a 35% solution of CH, a 35% solution of sodium chloride, or double-distilled water. Equal numbers of hamsters in each group were injected on the right or left side of the abdomen. Within 10 days, 35% of the CH-injected hamsters were dead or had to be euthanized. Autopsy revealed severe peritonitis and adynamic ileus. CH-injected hamsters that survived gained weight at a rate similar to that of the controls. All surviving hamsters were killed 18 days after the injections. Among the surviving CH-injected hamsters, 84.6% had intra-abdominal adhesions, 61.5% had unilateral testicular atrophy, and 53.8% had a yellowish necrotic mass in the epididymal fat pad (EFP). All the lesions occurred on the side that was injected. The atrophied testes had been rendered cryptorchid due to involvement with intra-abdominal adhesions. In the water-treated controls, there were no abnormalities; whereas, in the saline controls, 75% had a mass in the EFP. Histology of the EFP mass was similar in hamsters injected with CH or hypertonic saline and suggested a diagnosis of fat necrosis. The results suggest that the mortality, the intra-abdominal adhesions, and the unilateral cryptorchidism were caused by a single i.p. injection of CH, but the fat necrosis in the EFP was probably caused by high concentrations of salt. The results further suggest that high concentrations of CH should not be injected intraperitoneally for anesthesia in chronic studies, particularly of the male reproductive system.

The effects of chloroquine on pulmonary saccular growth near term.

The Antimalaria drug, chloroquine is an amphiphilic cationic compound and might therefore be suspected to interfere with foetal lung maturity as previously observed with other amphilphilic cationic drugs. Single doses of chloroquine phosphate (40mg/kg b. wt) was administered to pregnant rats on days 20 and 21 of gestation (term = 22 days). Morphometric analysis revealed a decrease in volume density (Vv) of parenchyma, saccular space and average saccular volume. Concurrent administration of single doses hydrocortisone on day 21 increased the Vv of the Parenchyma saccules and average saccular volume. This result suggests that the retardation of foetal lung maturity induced by chloroquine could be reversed by a concurrent administration of hydrocortisone. Questions concerning the mechanism by which these effects are produced must remain open.

Blockade of the selective increase in serum follicle-stimulating hormone concentration in immature female rats and its effects on ovarian follicular development.

We investigated whether administration of monosodium L-glutamate (MSG) to neonatal female rats would block the selective increase in serum follicle-stimulating hormone (FSH) concentration in immature rats in an attempt to provide a model in which to study the importance of the selective FSH rise on ovarian follicular development. In two separate experiments, s.c. injections of MSG (4 mg/g BW) on Days 1, 3, 5, 7 and 9 after birth blocked the selective increase in serum FSH concentration observed on Days 7 and 15 without blocking basal FSH secretion. Serum luteinizing hormone (LH) levels were unaffected in the first experiment and changed little in the second. MSG-treated rats had smaller ovaries on Days 15 and 23. The ovaries of MSG-treated rats on Day 15 showed decreased follicular growth as evidenced by a decrease in the number and percentage of follicles with diameters greater than 50 microns, in the number of follicles with greater than 1 layer of granulosa cells, and in the number of follicles beyond the primary stage of follicular development. These differences between MSG-treated rats and controls all but disappeared by Day 23. The results demonstrate that neonatal administration of MSG blocks the selective increase in serum FSH concentration in immature female rats and suggest that this selective increase in serum FSH levels plays a role in the normal acceleration of ovarian follicular development but is not needed for the development of preovulatory follicles by the sixth week after birth.

Basal gonadotropin hormone release rates during the period of selective follicle-stimulating hormone release in the juvenile female rat.

There are situations in which adult female rats release increased amounts of follicle-stimulating hormone (FSH) independent of increased luteinizing hormone (LH) release. This results from, at least in part, a selective increase in the basal FSH release rate. We investigated whether an increase in the basal FSH release rate is contributory to the rise in serum FSH levels which occurs independent of a rise in serum LH levels in the immature female rat. Rats had high serum FSH concentrations on days 7 and 15 after birth, low serum FSH levels on day 23, and low serum LH levels on all three days. In contrast, anterior pituitary gland (APG) FSH and LH concentrations and contents increased from day 7 to day 15 and the contents increased further from day 15 to day 23. Similarly, basal FSH and LH release rates per mg APG or per APG, as assessed by measurement of FSH and LH released into culture medium containing APG(s) from different aged rats, increased from day 7 to day 15 but did not increase further between days 15 and 23. The results indicate that unlike situations observed to date in adult female rats, a mechanism(s) other than an increase in the basal FSH release rate is involved in selective FSH release in the immature female rat.

An immunohistochemical study of adenohypophyseal cells containing follicle-stimulating hormone and luteinizing hormone during the phase of selective follicle-stimulating hormone release in postnatal female rats.

Serum concentration of follicle-stimulating hormone (FSH) in the juvenile female rat increases independently from that of luteinizing hormone (LH). The objective of this study was to determine whether this increase in serum FSH is accompanied by a proliferation of FSH-cells greater than the proliferation of LH-cells. Thus, we measured circulating FSH and LH in female rats on days 3, 10, 13, 17, and 20, calculated the percentages of adenohypophyseal cells that contained FSH or LH on days 3, 10, and 20, and determined whether cells containing only FSH existed on day 10. Serum FSH concentrations on days 10 and 13 were significantly greater than those on days 3, 17, or 20. No differences existed in serum LH concentrations. Cells containing FSH or LH were distributed throughout the entire adenohypophyses of 3, 10, and 20-day-old females. Clusters of these cells were observed in the ventral regions of adenohypophyses of 3-day-old females. The percentages of adenohypophyseal cells containing FSH increased significantly from approximately 9% in 3-day-old rats to approximately 17% in 10-day-old rats and then decreased to approximately 14% in 20-day-old animals. At all ages the percentages of adenohypophyseal cells containing FSH were similar to the percentages of cells containing LH. At 10 days of age, all cells containing FSH also contained LH and all cells containing LH also contained FSH. These data suggest that the increase in serum FSH in the juvenile female rat is associated with an increase in the percentage of adenohypophyseal cells containing FSH and that at this time all cells containing FSH also contain LH.

Monosodium L-glutamate administration: effects on gonadotrophin secretion, gonadotrophs and mammotrophs in prepubertal female rats.

We have studied gonadotrophin secretion and immunocytochemically stained gonadotrophs and mammotrophs in 35-day-old female rats which had been treated with monosodium glutamate (MSG) as neonates. We also compared our morphometric data in the saline-treated controls with those we have previously obtained in normal adult female rats. The size of the anterior pituitary glands was reduced but the serum levels, the pituitary gland concentrations and contents, and the in-vitro basal release rates of LH and FSH were not significantly altered by MSG treatment. The size of the LH and FSH cells was reduced by MSG administration, but the volume and numerical densities of LH and FSH cells, and the percentage of LH and FSH cells in the pars distalis were not affected. The results suggest that in spite of the smaller size of LH and FSH cells and of the anterior pituitary glands in the MSG-treated rats, the cells contain normal amounts of hormone and the basal LH and FSH secretion rates of the glands are not significantly depressed, contributing to the maintenance of normal serum gonadotrophin concentrations. The volume density of prolactin cells was not increased by MSG treatment. The volume density of gonadotrophs and the percentage of cells which are gonadotrophs in anterior pituitary glands of prepubertal female rats were greater than those in adult female rats, but the reverse was true for the volume density of prolactin cells, suggesting a reciprocal relationship between the relative numbers of gonadotrophs and mammotrophs in prepubertal and adult female rats.

Monosodium glutamate and pituitary gland luteinizing hormone (LH) release in response to LH-releasing hormone: an in vitro study.

We studied whether an increase in the basal LH release rate and/or the anterior pituitary gland (APG) LH response to LHRH is involved in maintaining normal or near-normal serum LH levels in monosodium L-glutamate (MSG)-treated rats which have small APGs for their body weight. Female rats were injected with MSG (4 mg/g BW) or saline on days 1, 3, 5, 7, and 9 after birth (day of birth = 0). At 8-9 weeks of age, saline-treated and MSG-treated rats were ovariectomized, and 7 days later, they were decapitated. Trunk blood was collected from 18 controls and 19 MSG-treated rats, and serum LH concentrations were measured by RIA. APGs were bisected and each hemi-APG was placed in culture medium for a 30-min preincubation period, followed by two 30-min incubation periods during which water or 10 or 30 ng LHRH were added to the medium. Despite the fact that the APGs of the MSG-treated rats were half the size of those of the saline-treated rats, the serum LH levels in the 2 groups were not different. Basal LH release rates (the response to water) and LHRH-induced LH release per mg APG were increased in MSG-treated rats. Calculation of the basal LH release rates and LHRH-induced LH release on the basis of the entire weights of the APGs showed no differences between the MSG-treated rats and the controls. In 6 additional control and 6 additional MSG-treated rats, the APG LH concentration was measured and was not different between the 2 groups. The results suggest that increases in both the basal LH release rate per mg APG and the amount of LH released per mg APG in response to LHRH are of importance in the maintenance of normal or near-normal serum LH concentrations in MSG-treated rats with small APGs.

Effects of neonatal administration of monosodium glutamate on somatotrophs and growth hormone secretion in prepubertal male and female rats.

Female and male rats were injected with monosodium L-glutamate (MSG; 4 mg/g BW) or 0.9% saline as neonates and then decapitated on days 35 and 40 of life, respectively. Trunk blood was collected for RIA of serum GH. Anterior pituitary glands (APGs) were bisected. One half was assayed for GH. The other half was placed in culture medium to study the basal GH release rate. Pituitary sections from additional rats were stained for GH, and morphometric analyses were performed on the GH cells. Treatment with MSG lowered serum GH levels and gland GH content in female but not in male rats. MSG did not alter the gland GH concentration or the basal GH release rate whether expressed per mg APG or per entire gland in either sex. The mean cross-sectional area of GH cells was reduced in either sex of MSG-treated rats. The numerical density of GH cells and the percentage of GH cells in APGs were similar in saline- and MSG-treated rats of either sex. The volume density of GH cells was lower in MSG-treated male rats only. The results suggest that in prepubertal rats which had been given MSG as neonates there is a sex difference in mean serum GH concentration and APG GH content, GH cell size is reduced in both sexes, and the individual GH cells contain normal amounts of GH in spite of their smaller size.

A decrease in thymus-mediated immune responses as a result of treatment of neonatal rats with glutamate.

We investigated whether administration of monosodium 1-glutamate (MSG) to neonatal rats would disrupt immune responses in intact and orchidectomized adult male rats. Neonatal male rats were treated with saline or MSG which causes severe endocrine abnormalities. Half of each group of animals were orchidectomized as adults and killed one week later along with intact rats. MSG treatment resulted in suppressed serum LH levels in intact rats. Thymus weight and spleen cellularity in intact animals were not affected by MSG treatment, but thymus weight increased within one week after orchidectomy in both saline- and MSG-treated groups. In intact rats, lymphocyte stimulation by the T cell specific mitogens (concanavalin A or phytohemagglutinin) or the B cell specific mitogen (lipopolysaccharide) was unaffected by prior treatment with MSG. However, MSG treatment blocked the decrease attributable to orchidectomy in concanavalin A and phytohemagglutinin stimulation of lymphocyte blastogenesis. The results suggest that administration of MSG to neonatal male rats can alter some immune responses in the adult animal.

Administration of monosodium glutamate to neonatal male rats: alterations in the gonadotrophs and in gonadotrophin secretion.

We have studied the effect of administration of L-monosodium glutamate (MSG) to neonatal rats on gonadotroph morphology and gonadotrophin secretion in the prepubertal male rat. Rats were injected with MSG (4 mg/g body weight) or with 0.1 ml saline/10 g body weight on days 1, 3, 5, 7 and 9 of life (day of birth = day 0) and were used for experiment on day 40. Trunk blood was collected from 8 saline- and 9 MSG-injected rats for assay of serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations. One-half of the anterior pituitary gland was assayed for LH and FSH concentrations and the other half was placed in culture medium for a 30-min preincubation and then placed in fresh medium for a 2-hour incubation (basal LH and FSH release). An additional 4 rats in each group were killed and the pituitary glands were prepared for histological examination and immunocytochemical staining of LH and FSH cells and morphometric examination of these cells at the light microscopic level. The morphometric analyses were compared with those performed previously by us on adult male rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Pars distalis cell quantification in normal adult male and female rats.

We analysed cell types in the pars distalis of normal young adult male and female rats with respect to their percentages and the relative volumes they occupy. In male rats the percentages of the cell types were: prolactin 49.80, GH 22.67, LH 5.04, FSH 4.22, ACTH 2.93 and TSH 2.09. The volume densities were: prolactin 20.48, GH 20.95, LH 7.34, FSH 6.73, ACTH 3.75 and TSH 3.19. In female rats the percentages of the cell types were: prolactin 52.40, GH 20.30, LH 5.89, FSH 4.06, ACTH 2.53, TSH 2.40 and the volume densities were: prolactin 28.09, GH 20.86, LH 8.11, FSH 5.46, ACTH 3.49 and TSH 2.91. The percentages of pars distalis cells which did not stain with the antisera to the six classical hormones were 17.47 in male and 16.48 in female rats. The results suggest that (1) in both sexes the number (N) of prolactin cells greater than N of GH cells greater than N of gonadotrophs greater than N of TSH or ACTH cells, (2) the percentage of each cell type was similar in both sexes, (3) the volume density (Vv) of prolactin cells was greater than the Vv of GH cells in female but not in male rats and in both sexes the Vv of GH cells greater than the Vv of gonadotrophs greater than the Vv of TSH or ACTH cells, (4) in both sexes the volume (V) of prolactin cells less than the V of GH cells less than the V of gonadotrophs, the V of TSH cells or the V of ACTH cells, (5) the V of prolactin cells was greater in female than in male rats and (6) approximately 17% of the cells in the pars distalis of both sexes did not contain 'immunoreactive' prolactin, GH, LH, FSH, TSH or ACTH.

The localization of gonadotrophs in normal adult male and female rats.

We investigated the localization of LH and FSH cells within the pituitary glands of normal adult rats. Groups of four female rats were decapitated at one of five different times during the estrous cycle. Four male rats were also decapitated. Paired horizontal flip-flopped serial paraplast sections from the dorsal, middle, and ventral portions of each pituitary gland were stained. For each pair, one section was stained with antirat LH-S4 and the other section with antirat FSH-S7, by the unlabeled antibody peroxidase-antiperoxidase method. All immunoreactive cells were counted, and the area of pars distalis in each section was determined. We studied the spatial distribution of gonadotrophs within the sections and determined if a polarization along the antero-posterior axis existed. In the "sex zone" of the pars distalis, the cross-sectional area of LH cells and the percentages of LH cells that also contained FSH and vice versa were determined and compared with those obtained from the entire pars distalis. Additional sections were stained for TSH, ACTH, GH, or PRL, and the distribution of stained cells was compared with that of those that stained for LH or LH/FSH, particularly in the sex zone and in the pars intermedia. The results indicate that 1) gonadotrophs are more evenly distributed dorsoventrally within the pars distalis of male rats than in that of female rats; 2) an antero-posterior polarity in gonadotropic distribution is more pronounced in male rats than in female rats; 3) gonadotrophs containing only LH are less numerous in male than female rats, and in the female tend to be centrally located within the pars distalis; 4) the sex zone contains PRL cells and gonadotrophs, and the percentages of gonadotrophs that contain LH or LH and FSH are not different from those of the entire pars distalis; 5) LH, and occasionally LH/FSH cells, are present between lobules of immunoreactive ACTH cells in the pars intermedia; and 6) LH cells in the pars intermedia are smaller than those in the sex zone or entire pars distalis.