Testosterone modifies response to chronic heat exposure in rats.

Eight weeks of heat exposure (34 +/- 0.5 degrees C) in sham-orchiectomized rats leads to an increase of body temperature, slowing of body growth rate, and decrease of serum corticosterone level, as compared with animals maintained at 21 +/- 2 degrees C. Orchiectomy decreases body temperature, slows growth rate, and increases plasma corticosterone concentration both in control and heat exposed animals. Testosterone administration reverts these parameters to initial values. We conclude that testosterone plays a role in the regulation of heat balance in male rats.

Tolerance to lipopolysaccharide is not related to the ability of the hypothalamus to produce prostaglandin E2.

The effects of repeated administration of Escherichia coli lipopolysaccharide (LPS) on body temperature and hypothalamic prostaglandin E2 (PGE2) production was examined in male Sprague-Dawley rats to elucidate whether the development of endotoxin tolerance is related to the ability of the hypothalamus to produce PGE2. Initial injection of LPS resulted in hyperthermia, preceded by short-termed hypothermia, while no changes in body temperature were observed after the second injection (administered 48 h later). In contrast, LPS induced elevation in hypothalamic PGE2 production after both the first and second injections of the pyrogen. This led us to conclude that endotoxin tolerance is independent of the hypothalamic production of PGE2 in response to repeated administration of LPS.

Intratesticular retention of sperm and premature decline in fertility in the domestic rooster, Gallus domesticus.

In domestic roosters, which were originally seasonal breeders and that are now kept under unnatural and unchanging conditions throughout the year, fertility peaks at 32 weeks of age (96%) but it subsequently declines rapidly to only 5% at 110 weeks despite the fact that roosters can live for about 10 years. Roosters exhibiting this low-fertility syndrome have reduced levels of spermatozoa in the ejaculate. Concomitantly, however, superabundant but apparently normal spermatozoa are found attached to Sertoli cells and, in addition, the seminiferous epithelium fails to show evidence of the regression of atrophy that characterizes both aging non-seasonal breeders and true seasonal breeders during non-reproductive periods. This syndrome of premature low fertility appears to stem from impaired spermiation with resultant retention of spermatozoa by Sertoli cells. To examine this problem, we compared intratesticular incorporation of 3H-thymidine between high-fertility (32-week-old) and low-fertility (82-week-old) roosters. Radioactivity associated with spermatozoa, 33 days post-injection, was almost 50% higher in the low-fertility roosters than in the high-fertility ones. By contrast, both groups showed similar characteristics with respect to a) intratesticular incorporation of 3H-thymidine, b) dynamics of spermatogenesis, c) intratesticular level of radioactivity just before the initiation of spermiation, and d) the duration of both spermatogenesis and the time required for sperm to pass through the genital tract. Our results confirm that intratesticular retention of sperm occurs in roosters with premature low-fertility syndrome and suggest new possibilities for the study of the complex relationship between Sertoli cells and spermatozoa and the effects of this relationship on fertility.

The effects of 1,2-dibromo-3-chloropropane (DBCP) on general toxicity and gonadotoxicity in rats.

This study was set to determine if there is a correlation between the general toxic effect and the gonadotoxic effect of DBCP on male rats. Groups of male rats were injected with a single dose of DBCP (50 mg kg-1) dissolved in dimethylsulfoxide (DMSO). Twenty four hours, one and four weeks post injection animals were sacrificed. Blood was collected for enzymes' and hormones' assays. Organs were weighed and testes were taken for histological examination and sperm counts. The results showed that DBCP at a dose of 50 mg kg-1 had a general toxic effect expressed by reduction in body and liver weights and reduced activities of serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT). These changes show a tendency to revert to normal values with time. On the other hand, gonadotoxic effects increase in severity with time. The weight of testes and epididymides were reduced, sperm counts decreased and histological damage advanced, and FSH and LH blood levels increased 4 weeks post injection. It seems that in rats the gonadotoxic effect of DBCP is dissociated from the general toxic effects.

Neonatal low-dose gamma irradiation-induced impaired fertility in mature rats.

The reproductive capacity of mature rats at the age of 8 days was studied following neonatal exposure to 0.06 Gy dose of gamma-radiation. Decreased litter size and reduced body weight of the pups on weaning day, but not at parturition, were observed in female rats. The reduced litter size was not associated with impaired ovulation, impaired uterine implantation or mortality in utero, but resulted from increased death rate or at near parturition. Of the neonatally irradiated males 29% were found to be sterile and had degenerated or necrotic testes. The testicular damage and the reduced growth rate of the offspring of the irradiated females demonstrate the extreme sensitivity of the immature reproductive system to ionizing radiation, even at very low doses.

Age-dependent differences in the effects of 1,2-dibromo-3-chloropropane (DBCP) on fertility, sperm count, testicular histology and hormonal profile in rats.

This study was set up to determine if there are any age-dependent differences in the adverse effects of DBCP on the reproductive system of male rats. Groups of male rats were injected at the ages of 7,30 or 90 days with a single (50 mg kg-1 body weight) or repeated (20 mg kg-1 body weight once a week for 3 weeks) dose of DBCP, dissolved in DMSO. Ninety days after the last injection the males' fertility was estimated and the animals were killed. Blood was collected for future hormone assays, organs were weighed, testes were then taken for histological studies and sperm counts. The results were compared with those of control peers. The results showed that animals injected at the ages of 7 or 90 days under both regimens of treatment were adversely affected. The damage was noted in their fertility rate, sperm production, testicular histology and hormonal profile. Those injected at the age of 30 days showed only an insignificant variation compared with controls.

Progesterone and estradiol plasma levels in neonatally irradiated cycling rats.

Female rats which were exposed to a single low dose of gamma irradiation (6R or 15R) at the age of 8 days produce smaller litters when mature than untreated controls. The possibility that the impaired fertility resulted from altered ovarian activity as reflected by changes in plasma levels of progesterone or estardiol was investigated. Plasma levels of both steroids were determined throughout the day of proestrus. Progesterone level was also determined in 6R animals on the day of weaning. The maturity of such irradiated rats was assessed by observing the time of vaginal opening. The results indicated that the preovulatory peak of progesterone was delayed in the 6R rats whereas in the 15R group its levels were significantly lower. On the other hand no differences in estradiol plasma levels were noticed between the groups. The higher level of progesterone in the 6R animals was not evident on the day of weaning and was even in both groups, but vaginal opening in the irradiated rats was significantly delayed. The elevated level of progesterone might be responsible, among other endocrine changes, for the lower fertility of neonatally irradiated mature female rats.

Ultrastructure of testicular cells in rats treated with dibromochloropropane (DBCP).

Three days after a single injection of rats with dibromochloropropane (DBCP) the testicular seminiferous tubules displayed focal damage, which became more pronounced six days after the treatment. Severely damaged tubules exhibited an almost complete exfoliation of the germ cells, while the Sertoli cells' lining remained mostly intact. The most affected germ cells were the spermatids. The mitochondrial sheath of the midpiece was often incomplete, vacuolated and/or broken into several pieces. In many cases the mitochondrial sheath protruded towards the interior, thus partially separating dense fibers 1, 2 and 9 from 3 to 8. In addition, cross sections revealed several midpieces of different flagellae surrounded by a single plasmalemma. In young spermatids, an atypical acrosome formation was noted concomitantly with a progressive emptying of the central nuclear region. This resulted in nuclei with electron lucent center surrounded by a chromatin belt. Sertoli cells displayed intense phagocytotic activity, their cytoplasm containing increased numbers of lysosomes, cellular debris and axonemal fragments.

Changes in the endocrine system controlling reproduction in mature female rats neonatally exposed to a low dose of gamma irradiation.

Female rats which were exposed to a single low dose of gamma irradiation (6R or 15R) at the age of 8 days produce smaller litters when mature than untreated controls. The possibility that such an impaired reproductive performance could result from changes in the endocrine system was investigated. Plasma levels and hypophyseal contents of LH and FSH, plasma levels of testosterone and hypothalamic content of GnRH were determined. The responsiveness of the pituitary to a single injection of GnRH (50 ng/rat) given on day of proestrus was evaluated. The results indicated that plasma levels of FSH but not of LH were lower in the irradiated rats. This was accompanied by changes in the hypothalamic content of GnRH. The possibility that the pituitary was sensitive to gamma irradiation was excluded. Twenty five minutes after a single injection of GnRH a 2-5 fold increase in LH plasma levels was noticed in all the groups, thus indicating that the reduced fertility could not be attributed to hypophyseal malfunction but rather to an impaired hypothalamic stimulus. Moreover, the lower levels of FSH might result from the significantly elevated levels of testosterone which were observed in the irradiated rats. Apparently, neonatal exposure to a single low dose of gamma irradiation resulted in a new hormonal equilibrium which was responsible for the reduced fertility in such rats.

Testicular damage development in rats injected with dibromochloropropane (DBCP).

Dibromochloropropane (DBCP) is an effective nematocide which was shown to suppress spermatogenesis and cause infertility in men and rats exposed to the compound. These damages were described only after 6-8 weeks post injection. The present study was set to detect the early development of the testicular damages. Rats were injected s.c. with DBCP 50 mg/kg. Control animals were injected with the vehicle alone (DMSO). Groups of animals were sacrificed 24 h, 1, 2, 3 and 4 weeks post injection. Body weight of DBCP treated animals was reduced from the second week post injection. Organs' weights of the DBCP treated rats, corrected for differences in body weights, were similar to those of controls. Four weeks post injection testes and accessory gland weights were significantly reduced as compared with controls. Percentage of damaged tubules in the DBCP treated animals were elevated from 16.6 +/- 3.5 at the first day to 70.2 +/- 6.4 at the 4th weeks. Concomitantly with the advance of tubular damage was a reduction in epididymal sperm count in the DBCP treated rats. One week post injection histological changes were evident. These included multinucleated giant cells and tubules blocked with sperm granuloma. It seems that alterations of spermatogenesis appear earlyer and are already noticeable one week post injection.

The effect of dibromochloropropane (DBCP) on in vitro cyclic AMP levels and testosterone production in rat testes.

Adult male rats were injected s.c. once a week for 3 weeks with DBCP, 20 mg/kg BW. Animals were sacrified 20 weeks after last injection. Body and testes weights were recorded and testes were taken for standard histological preparation and for in vitro experiments. The in vitro experiments were carried out on testes slices (90-110 mg) incubated for 3 h with or without the addition of hCG to the incubation medium. Cyclic AMP content of the tissue as well as testosterone released into the incubation medium were determined. Testes weights of DBCP treated animals were 68% lower than that of controls. All semiferous tubules were damaged and shrunken, thus, their number per microscope field was 2.6 times that of controls. Cyclic AMP levels in testes slices were similar in both DBCP treated and controls. The addition of hCG stimulated cyclic AMP accumulation to a much higher level in the DBCP treated than in controls. When calculated per one pair of testes the content in unstimulated pair was more than twice that of DBCP treated. Stimulation of hCG increased both DBCP treated and controls to similar levels. Testosterone release into the medium by slices was higher in DBCP treated than in controls and so was also the increment due to hCG stimulation. Similar results were obtained when testosterone release was calculated per one pair of testes. It is suggested that since the major testicular compartment damaged by DBCP is the tubular one, the proportion of the interstitium per testicular unit weight is larger than in controls, thus, cyclic AMP content increment due to hCG stimulation is much higher.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive performance of dibromochloropropane-treated female rats.

Dibromochloropropane (DBCP) is an effective nematocide which has been shown to suppress spermatogenesis and cause infertility in both men and male rats. There are no similar reports concerning the effects of DBCP on female reproduction. The purpose of the present study was to attempt to interfere with the various phases of oogenesis. Proestral or pregnant rats were injected subcutaneously once with 40 mg/kg DBCP on one of each days of L12-L20 of gestation; a double dose (80 mg/kg) was injected in eight consecutive days (L11-L18). In addition, L13 fetuses were injected--directly into the amniotic sac--with 0.1 mg DBCP. Pooled data from the various days of gestation revealed that postimplantation losses were three times as high in the DBCP-treated animals as in DMSO-treated controls. Perinatal deaths were 58% higher and mean pup weights were 30% lower in the DBCP-treated rats than in controls. The reproductive performance of females exposed to DBCP while in utero was affected only to a limited degree (reduced number of ovulations and implantations) as compared with their DMSO counterparts. Doubling the dose (80 mg/kg) seriously reduced the birth weight of pups (50% of controls), all of which died within several hours post-partum. Direct injection of DBCP into embryos or to proestral rats did not have any adverse effects on their future reproductive performance. In contrast to the effect on spermatogenesis, it appears that oogenesis and ova are unaffected by DBCP.

Dissociating antifertility effects of GnRH-antagonist from its adverse effects on mating behavior in male rats.

Antagonist analogues of gonadotropin-releasing hormone (GnRH-A) alone inhibit spermatogenesis in experimental animals, but concomitant decline in serum testosterone leads to abolition of mating behavior. We assessed if the antifertility effects of GnRH-A could be dissociated from its effects on mating behavior by combining it with a small dose of androgen. Seven groups of six adult male Wistar rats were treated for 70 days as follows: I) controls, II) GnRH-A alone (250 micrograms/day), III) GnRH-A + 0.05 mg testosterone enanthate (TE), IV) GnRH-A + 0.15 mg TE, V) GnRH-A + 0.50 mg TE, VI) GnRH-A + 1.50 mg TE, and VII) GnRH-A alone (recovery group). Testes, prostate, and seminal vesicle weights were markedly reduced by GnRH-A treatment alone. Doses of TE required to maintain prostate and seminal vesicle weights were between 0.15 and 0.50 mg. Testis weights were not restored to normal even by the highest dose of TE. Intratesticular sperm counts were markedly decreased by GnRH-A treatment and restored only at the highest dose of TE (1.50 mg). Five out of six animals in group II, six out of six animals in group III, and one out of six in group IV were azoospermic. When mated with normal females, all animals in groups I and VI were fertile, all animals in groups II, III, and IV were infertile, whereas only four out of six animals in group V were fertile. All measures of mating behavior were impaired by GnRH-A treatment and restored by the smallest dose of TE (0.05 mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Altered ovarian responsiveness to gonadotropins in neonatally irradiated immature rats.

Female rats which were exposed to a single low dose of gamma irradiation (6R or 15R) at the age of 8 days produce smaller litters when mature than untreated controls. In order to study the possibility that such an impaired reproductive performance could result from a reduced ovulation rate, neonatally irradiated females were treated with PMSG (12 iu/rat) at the age of 26 days. Another group of rats, similarly treated, was further injected with hCG (5 iu/rat) 48 hours later. Animals were killed 48, 55, 60 and 72 hours after PMSG treatment or 72 and 120 after hCG injection. The results indicated that PMSG treatment increased the ovarian weight of non-irradiated controls as well as of irradiated rats and in all animals induced a proestrus like profile of LH. Only a combined treatment of PMSG and hCG resulted in ovulation and corpora lutea formation with significantly increased numbers of corpora lutea in the ovaries of the irradiated rats. The latter was associated with higher progesterone plasma levels not correlated to the number of corpora lutea. The gradual decrease in the number of ovarian binding sites for hCG with increased radiation dose and the increased association constant in the 15R group could not explain the increased sensitivity of the ovary to exogenous gonadotropins which results from neonatal exposure to low doses of gamma irradiation.

Pregnancy outcome in heat-exposed hamsters; the involvement of the pineal.

The effect of high ambient temperature (34 degrees C) on the function of the female reproductive system, on embryonic development and on outcome of pregnancy, was investigated in heat-exposed sham-operated (Sh) and pinealectomized (Px) golden hamsters maintained under short photoperiod. Plasma prolactin levels were reduced in both heat-exposed groups (ShH and PxH) but pituitary prolactin was increased in the pinealectomized groups irrespective of ambient temperature (21 or 34 degrees C). Pituitary weights and LH contents were not affected in any test group. Heat exposure brought about a reduction in the number of corpora lutea and of pups born, the latter being more drastically reduced in absence of the pineal; the depressant effect of heat on ovarian weight was evident only in the pinealectomized animals. Progesterone levels were not affected in any test group and pregnancy was not prolonged, thus, it would seem that pregnant hamsters adapt themselves well to heat. Moreover, high ambient temperature promoted a rise in pineal. HIOMT activity and boosted cortisol levels in presence of the pineal gland only, which, together with the above findings, shows that the pineal can provide protection for pregnant hamsters against adverse effects of high ambient temperature.

Long term effects of dibromochloropropane (DBCP) on male rats' reproductive system.

Adult male rats were injected s.c. once a week for 3 weeks with DBCP, 20 mg/kg B.W. Animals were sacrificed 5, 9, 13, 17, 25 and 50 weeks after last injection. Body weight was recorded once a week. Prior to sacrifice each male was presented with proestral females in order to determine the male's mating behaviour and fertility. Testes were removed, weighed and taken for standard histological examination. DBCP treatment caused a reduction of body weight which reverted back to control levels some 17 weeks post injection. Testes weights were reduced and remained low despite the recovery of body weight. Generally, all males showed normal mating behaviour but most of them were infertile. Testicular histology showed a correlation between decreasing testicular weight and increasing percentage of degenerated seminiferous tubules, which was on the other hand correlated with decreasing tubular diameter. Serum levels of FSH and LH were significantly increased in the infertile DBCP treated males while values for the fertile ones were similar to those of controls. There were no differences in serum testosterone levels between DBCP treated and control animals. It is concluded that in DBCP treated rats testicular degenerative damages are associated with increased circulating gonadotrophin levels and with normal testosterone levels. Although mating behaviour is unaffected fertility is depressed and does not recover for at least 50 weeks post injection. It is suggested that DBCP treatment affects mainly the activity of the Sertoli cells while the Leydig cells are affected to a much lesser degree.

Gonadotoxicity and kinetics of dibromochloropropane in male rats.

Adult male rats were injected with [3H]dibromochloropropane dissolved in dimethylsulfoxide containing about 10 X 10(6) dpm. Blood from the tail and 24-h urine samples were collected up to 2 days post-injection. Tissue samples were further taken from the kidneys, liver, spleen, adrenals, epididymis, seminal vesicles and testes 7 h and 7 days post-injection. The results demonstrate that there is no preference in labelling of the testes compared with other organs, and the kidney and liver may have an important role in the elimination of DBCP.

Testicular modulation of luteinizing hormone response to gonadotropin-releasing hormone (GnRH)-agonist treatment.

We and others have observed that the response of serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to chronic gonadotropin-releasing hormone-agonist (GnRH-A) treatment is substantially different in normal compared to hypogonadal males. These data suggested that products of the testes determine the gonadotropin response to GnRH-A. The present studies were designed to determine whether this effect is mediated by products of the interstitial (steroids) or the tubular compartment. To create experimental states with selective impairment of interstitial, tubular, or both compartments, 100 male sexually mature Wistar rats were divided into five groups: I, intact; II, castrated; III, castrated with 20-mm testosterone (T) implants; IV, bilaterally cryptorchid; and V, ketoconazole-treated animals. Cryptorchid animals have been shown to have impairment of tubular function while ketoconazole inhibits T biosynthesis. Each of the 5 groups was divided into 2 subgroups to receive daily injections of either saline or 1 microgram of a potent GnRH agonist, D-leu6 des-Gly10 GnRH N-ethylamide, for 4 wk. Unlike the intact animals, which showed an elevation of basal serum LH concentration after 4 wk of GnRH-A treatment, the castrated animals showed significant suppression below baseline. Animals with preferential impairment of tubular function (cryptorchid and castrated + T) also showed significant suppression of LH after GnRH-A treatment. However, the ketoconazole-treated animals (with inhibition of T biosynthesis and intact tubular function), behaved similarly to intact animals and demonstrated an elevation of LH after GnRH-A treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal clearance of urea, inulin, and p-aminohippurate in heat-acclimated rats.

Clearance values of urea, inulin, and p-aminohippurate (PAH) were measured in heat-acclimated (HA) rats exposed for 3 wk to 35 degrees C, in control rats (C) exposed to 23 degrees C, and in HA rats deacclimated (DA) for 3 wk. In HA rats, urea clearance was lower by 73%, inulin clearance by 61%, and PAH clearance by 56%, compared with C rats. The clearance values of these substances returned to the control values in DA rats. The data suggest that the low clearance values reflect both reduced renal blood flow and possible changes in the capacity of the glomeruli for filtration and the tubules for either reabsorption or secretion.