Age-dependent effect of Freund's adjuvant on 24-hour rhythms in plasma prolactin, growth hormone, thyrotropin, insulin, follicle-stimulating hormone, luteinizing hormone and testosterone in rats

The effect of Freund's adjuvant administration on 24-hour changes of plasma prolactin, growth hormone (GH), thyrotropin (TSH), insulin, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone were studied in young (2 months) and aged (18 months) male Wistar rats. Rats were injected s.c. with Freund's adjuvant or adjuvant's vehicle and, 18 days later, they were killed at 6 different time intervals throughout a 24-hour cycle to measure circulating hormone levels by specific RIAs. Young rats receiving adjuvant's vehicle exhibited significant time-of-day-dependent variations in plasma TSH, LH and testosterone, with maximal levels at 1300 h, 0100 h and 1700 h, respectively. Prolactin and insulin levels, analyzed globally in a factorial ANOVA, showed significant time-of-day changes with maximal levels at 1300 - 1700 h and 2100 h, respectively. The daily rhythms in plasma LH and testosterone found in young rats were not longer observed in Freund's adjuvant-injected rats, while as far as TSH, a second peak was observed at 0100 h after Freund's adjuvant administration. Twenty-four hour rhythms in circulating TSH, LH and testosterone were blunted in old rats receiving either Freund's adjuvant or its vehicle. Aged rats exhibited significantly higher circulating levels of prolactin, and lower levels of GH, TSH, FSH and testosterone. The results indicate that secretion of prolactin, GH, TSH, FSH and testosterone are age-dependent, as are the responses of TSH, LH and testosterone to Freund's adjuvant administration.     

The effects of neonatal androgenization of male rats on testosterone metabolism by the hypothalamus-pituitary-gonadal axis

Male rats were androgenized on the third postnatal day by a single injection of 1 mg testosterone propionate. The in vitro metabolism of [4-14C]testosterone by pituitary and hypothalamus homogenates was investigated at the age of 90 days. The pituitary and hypothalamus homogenates from control and neonatally androgenized animals converted [4-14C]testosterone to the same metabolites, mainly 5 alpha-reduced derivatives; the quantitative yield of 5 alpha-reduced metabolites was much higher in the pituitary homogenates of androgenized rats. The hypothalamic homogenates showed no differences. In the androgenized rats a very significant increase of the plasma FSH levels was measured while the LH levels were also augmented. The plasma levels of testosterone were not different from the values in control rats, notwithstanding a 25% reduction in testes weight. The present experiments appear to indicate that the neonatal androgenization results in an accentuation of the sexual dimorphism which normally exists in the pituitary of adult rats for the 5 alpha-reductase activity.     

Reduced intrafollicular androstenedione and estradiol levels in early-treated prenatally androgenized female rhesus monkeys receiving follicle-stimulating hormone therapy for in vitro fertilization

Five early-treated and four late-treated prenatally androgenized and five normal female rhesus monkeys were studied to determine whether prenatal testosterone propionate exposure beginning Gestational Days 40-44 (early-treated) or 100-115 (late-treated) affects follicular steroidogenesis during recombinant human FSH (rhFSH) treatment. All monkeys underwent rhFSH injections, without human chorionic gonadotropin administration, followed by oocyte retrieval. Serum FSH, LH, estradiol (E2), progesterone (P), 17alpha-hydroxyprogesterone (17 OHP), androstenedione (A4), testosterone, and dihydrotestosterone were measured basally during rhFSH therapy and at oocyte retrieval. Follicle fluid (FF) sex steroids, oocyte fertilization, and embryo development were analyzed. Circulating FSH, E2, 17 OHP, A4, and dihydrotestosterone levels increased similarly in all females. Serum LH levels decreased from basal levels in normal and late-treated prenatally androgenized females but were unchanged in early-treated prenatally androgenized females. Serum P levels at oocyte retrieval were comparable with those before FSH treatment in all females. All prenatally androgenized females showed reduced FF levels of A4 and E2 but not P or dihydrotestosterone. Intrafollicular T concentrations also were significantly lower in late-treated compared with early-treated prenatally androgenized females or normal females. In early-treated prenatally androgenized females, but not the other female groups, intrafollicular A4 and E2 levels were reduced in follicles containing oocytes that failed fertilization or produced zygotes with cleavage arrest before or at the five- to eight-cell embryo stage. Therefore, in monkeys receiving rhFSH therapy alone without human chorionic gonadotropin administration, early prenatal androgenization reduced FF concentrations of E2 and A4 in association with abnormal oocyte development, without having an effect on P, testosterone, or dihydrotestosterone concentrations.     

Effect of neonatal androgenization on the testosterone feedback sensitivity in adult rats in two lighting conditions

Neonatally androgenized and intact adult male Wistar rats received daily, during 1 week, either testosterone propionate or sesame oil injections in periodic or constant light. Serum and pituitary gonadotropins and hypothalamic LHRH were measured. In periodic light, neonatal androgenization did not change the serum concentration or pituitary contents of gonadotropins, or the hypothalamic content of LHRH. Testosterone injections decreased serum concentration and pituitary content of gonadotropin of intact rats but failed to decrease the pituitary gonadotropin content of neonatally androgenized rats. In constant light, serum FSH was decreased in neonatally androgenized rats. Testosterone injections decreased both serum LH and FSH concentrations of intact rats but only serum LH of androgenized rats. Pituitary gonadotropin and hypothalamic LHRH contents remained unchanged. We conclude that neonatal androgenization renders the male rat hypothalamo-pituitary axis more resistant to changes of testosterone concentration in adulthood. Constant light did not sensitize the neonatally androgenized rats to testosterone, but on the contrary, testosterone injections were less effective in constant than in periodical light.     

Influence of neonatal androgenization on the testicular steroidogenesis in the adult rat

The in vitro testicular steroidogenesis of male rats, androgenized on the third postnatal day by a single injection of 1 mg testosterone propionate, was investigated when the animals were 100 days old. The neonatal androgenization resulted in a 25% lower testes weight, significantly increased plasma levels of FSH (P less than 0.01) and LH (P less than 0.02), and normal levels of testosterone. Although the testes were hypotrophic, the incubation of the testes pairs yielded the same amounts of testosterone, 7 alpha-hydroxytestosterone and 5 alpha-androstane-(3 alpha + 3 beta), 17 beta-diol as in the control animals. However, the steroidogenic response to an acute hCG stimulation was reduced. From incubations of testes homogenates with various labelled steroid precursors it could be inferred that the activity of the 17 alpha-hydroxylase, the 3 beta-hydroxysteroid dehydrogenase-isomerase and the 17 beta-hydroxysteroid dehydrogenase, expressed per unit of incubated protein, was significantly increased in the testes of the androgenized rats. These data indicate that the basal steroidogenesis in neonatally androgenized male rats is maintained by an increased synthesis per unit of tissue, possibly under influence of an increased gonadotrophic stimulus, but that the maximum steroidogenic capacity is reduced.     

Age difference in the response to synthetic luteinizing hormone-releasing hormone (LHRH) in androgenized rats with special reference to the dose of testosterone propionate for androgenization.

Five-day-old female rats were androgenized with 1,000 or 100 microgram testosterone propionate and were examined regarding the response to LHRH at 4, 7 and 12 weeks of age by measuring peripheral LH concentrations. The order of magnitude in LH release was 7 greater than 4 greater than 12 weeks old, whereas in normal rats, 4 greater than 12 greater than 7 weeks old. LH release in 4- and 7-week-old rats was higher than that in normal controls at the respective age, but was much lower than that in normal controls 12 weeks old. The LH release by Des-Gly10-(D-Ala6)-LHRH-ethylamide (TAP127) was greater than that by natural LHRH both in normal and androgenized rats at 7 or 12 weeks old. The results indicate that the pituitary gland in androgenized rats responds to LHRH to a much larger extent during the premature period and its responsiveness declines during the course of maturation. A marked hypersensitivity was observed in 7-week-old rats androgenized with 100 microgram testosterone propionate. The process of androgenization may include the induction of alterations in the sensitivity of the pituitary to LHRH and probably in the LH synthesizing ability of the pituitary.     

Physiological role of putative testicular gonadotrophin releasing hormone (GnRH)

Evidence suggests that exogenous GnRH and agonist analogues have short-term stimulatory effects on rat Leydig cell function - when administered intratesticularly. Since rat Leydig cells possess GnRH receptors and their endogenous ligand has not yet been identified the physiological importance of the observations for testis function is unknown. To address this issue we have determined the consequences of blockade of testis GnRH receptors on Leydig cell function under both normogonadotrophic and hypogonadotrophic stimulation of the testis in vivo. A GnRH antagonist (ANT) was used to achieve receptor blockade but during continuous systemic infusion ANT occupied pituitary GnRH receptors and markedly reduced serum LH, FSH, testosterone, and intratesticular testosterone in adult and 30 d old immature male rats. These results were similar to those obtained by administration of a GnRH antiserum which did not bind to testis GnRH receptors. Thus, blockade of testis GnRH receptors during hypogonadotrophism did not produce additional inhibition of steroidogenesis by Leydig cells. However, direct continuous infusion of ANT into one testis produced greater than 90% occupancy of GnRH receptors while reducing GnRH receptors by only 50% in the contralateral testis. Unilateral intratesticular infusion did not reduce serum LH, FSH, Prolactin or testosterone levels despite 75% occupancy of pituitary GnRH receptors. Thus, both ANT infused and saline infused testes were exposed to the same gonadotrophic stimulants but in the former GnRH-R were essentially non-existent. Compared to the control testis, the ANT infused testis showed a 20-30% reduction in LH, FSH, lactogen receptors and 30-40% fall in testosterone content. Identical results were obtained in adult and 30 d-old male rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

A role for inhibin in the control of follicle-stimulating hormone secretion in male rats

We examined the relationship of testosterone (T) and porcine follicular fluid (pFF) in the negative feedback control of FSH and LH secretion in adult male rats. Either at the time of castration (acute) or at least 30 days after castration (chronic), we implanted T-filled Silastic capsules, which were 2 mm, 10 mm, or 30 mm long; empty capsules (30 mm) served as controls. Seven days later, we injected either 0.15 ml of pFF or saline (i.v.), decapitated the rats 6 hours later, and collected trunk blood for subsequent serum analysis of FSH, LH, and T by RIA. In the acute groups, T implants suppressed the postcastration rises in plasma FSH and LH levels in a dose-dependent manner, with only the largest implant, 30 mm, able to return them to intact levels. PFF injection significantly suppressed FSH levels in intact and acute rats but had no effect on serum LH. In chronic rats, T therapy for 7 days suppressed plasma LH levels in a dose-dependent relationship, yet did not do so to plasma FSH levels. FSH levels were significantly higher in rats with the 30 mm T implants than in intact rats, but were significantly suppressed as compared to chronic controls. PFF significantly suppressed serum FSH levels in all chronic groups with the chronic controls showing the greatest amount of suppression. We conclude that the role for inhibin in the normal control of FSH secretion is that of a secondary modulator which is superimposed on, yet independent of, the steroid feedback mechanism. At any given moment this modulation is dependent upon the secretory activity of the FSH gonadotrope.     

Effect of prenatal treatment with busulfan on the hypothalamo-pituitary axis, genital tract and testicular histology of prepubertal male rats

Female Wistar rats were treated with busulfan or with solvent on Day 20 of pregnancy. Thirty male offspring of each group were killed at 38 days of age. In busulfan-treated rats, compared to controls, hypothalamic LH-RH content was decreased by 52%, whereas pituitary LH and FSH concentrations were increased by 60 and 43% respectively. Plasma LH and FSH were increased by 112 and 275% respectively. Prolactin concentrations were not changed, but plasma testosterone concentration was decreased by 48%. The total number of Leydig cells per testis was decreased by 52%, and LH binding sites per testis were decreased by 70%. The total number of Sertoli cells was decreased by 44%, while FSH binding sites per testis were decreased by 62%. Spermatogenesis was practically absent after prenatal exposure to busulfan. These data demonstrate that on Day 20 of pregnancy all the dividing cells in the fetal testes were depleted by an antimitotic treatment. The stimulation of the hypothalamo-pituitary axis could have been partly induced by the decrease in testosterone production, and by the aplasia of germ cells involving modifications of the remaining Sertoli and Leydig cells.     

Profiles of luteinizing hormone, follicle-stimulating hormone, testosterone and prolactin in rams of diverse breeds: effects of contrasting short (8L:16D) and long (16L:8D) photoperiods

Mature rams of Polled Dorset, Finnish Landrace, Rambouillet and Suffolk breeding were maintained in a temperature-controlled environment and exposed to two consecutive cycles of short (8L:16D) followed by long (16L:8D) days. Serum hormone concentrations were determined in weekly samples and in 24-h profiles characterized at the end of each lighting schedule (i.e., 12, 24, 36 and 48 weeks). In all four breeds, the pituitary-testicular axis was more active during short days as compared with long days and the magnitudes of changes in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone concentrations were greater for the two most seasonal breeds, Finnish Landrace and Suffolks. In comparison to other breeds, Finnish Landrace rams had significantly (P less than 0.05) higher mean LH levels, showed the greatest number of LH peaks/24 h, and had the highest mean testosterone levels at the end of both periods of short days, while Rambouillet rams had significantly (P less than 0.05) lower testosterone. Rambouillets also showed the smallest changes in pulsatile LH and testosterone secretion and displayed the least number of LH peaks/24 h following short days. Serum FSH levels were significantly (P less than 0.05) higher in Finnish Landrace and Suffolk rams than in Polled Dorsets and Rambouillets after 12 weeks of short days. Breed differences in serum LH, FSH and testosterone were not apparent following long days. Prolactin levels in Rambouillet rams were significantly (P less than 0.05) lower than in the other breeds following both periods of long days. These results indicate that breed differences exist in mature rams with regard to hormone secretory profiles. Breed differences in serum gonadotropin and testosterone are only apparent during short days when the hypothalamo-pituitary-testicular axis in rams is considered most active. Likewise, breed differences in prolactin are noticeable only during long days when secretion of this hormone is enhanced. Breed differences in LH, FSH and testosterone secretion in rams during short days might be related to seasonality of mating and/or fecundity of breed types.     

Selective failure of androgens to regulate follicle stimulating hormone beta messenger ribonucleic acid levels in the male rat

FSH beta, as well as LH beta, and alpha-subunit mRNA levels were examined in the pituitary glands of male rats after sex steroid replacement at various times (7, 28, or 90 days) after orchiectomy. Testosterone propionate, dihydrotestosterone propionate, or 17 beta-estradiol benzoate (E) were administered daily for 7 days before killing, to assess the role of different gonadal steroids on gonadotropin subunit mRNA levels. Subunit mRNAs were determined by blot hybridization using rat FSH beta genomic DNA, and alpha and LH beta cDNAs. At all time points, alpha and LH beta mRNAs increased after gonadectomy and fell toward normal levels with either androgen or estrogen replacement. FSH beta mRNA levels increased variably postcastration: 4-fold at 7 days, 2-fold at 28 days, and 4- to 5-fold at 90 days. Although E replacement uniformly suppressed FSH beta mRNAs, neither testosterone propionate nor dihydrotestosterone propionate administration suppressed FSH beta mRNA levels at any time point after orchiectomy. These data demonstrate that there is a relative lack of negative regulation of FSH beta mRNA levels by androgens in a paradigm in which E administration results in marked negative regulation of FSH beta mRNA levels. Thus, in the male rat, estrogens negatively regulate all three gonadotropin subunit mRNA levels while androgens negative regulate LH beta and alpha-subunit but fail to suppress FSH beta mRNAs.     

The effects of long-term administration of either a crude inhibin preparation or an antiserum to FSH on serum hormone levels, testicular function and fertility of adult male rats.

Adult male rats were given either daily injections of ram rete testis fluid for periods of up to 70 days or injections of an antiserum against FSH every 3 days for 90 days. Compared with the control groups, the rats injected with ram rete testis fluid had lowered serum FSH levels, but only at treatment periods of 30 days and less. The levels of LH and testosterone in serum, testicular fluid secretion, sperm counts, testis weights and fertility were not affected by rete testis fluid treatment. The rats injected with anti-FSH serum exhibited an impairment of fertility which was never complete and evident only after 49 days of treatment. After 90 days of anti-FSH treatment, testis weight and free serum FSH were reduced, but sperm counts, testicular fluid secretion and serum levels of LH and testosterone were not affected.     

Androgens positively regulate follicle-stimulating hormone beta-subunit mRNA levels in rat pituitary cells

We have shown previously that androgens negatively regulate LH alpha and beta-subunit mRNA levels, but have little or no effect on FSH beta mRNA levels in rats in vivo. In contrast, estrogen negatively regulates all three gonadotropin subunit mRNA levels in vivo. We have examined the effects of these sex steroids on gonadotropin subunit synthesis directly at the level of the pituitary gland by using cultured rat pituitary cells. Adult female and male rat pituitaries were dissected, dispersed enzymatically, and maintained in culture for 2 days. At that time, cells were treated for varying lengths of time with either medium alone or sex-steroid hormone treatments (estradiol or testosterone). Dose-response and time-course experiments were performed. Cells were then harvested and total RNA was extracted. Gonadotropin subunit mRNA levels were assessed by blot hybridization techniques. Sex-steroid hormones were added to achieve final concentrations ranging from 10(-12) to 10(-6) M for dose response experiments and 10(-8) M for time-course experiments. Testosterone treatment (10(-8) M) increased FSH beta mRNA levels 3-fold in females (P less than 0.01) and males (P less than 0.05), but had no effect on alpha or LH beta mRNA levels in either sex. Dose-related increases in FSH beta mRNA levels with increasing concentrations of testosterone were observed in both female and male pituitary cell cultures. Time-course studies revealed that the testosterone-stimulated increases in FSH beta mRNA levels are statistically significant by 12 h and 6 h after hormone addition in female and male cultures, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Follicle-stimulating hormone secretion in monosodium glutamate-lesioned rats: response to unilateral gonadectomy or porcine follicular fluid (inhibin)

The purpose of this study is to determine the acute response of pituitary FSH and LH release to unilateral gonadectomy in the MSG-treated rat, and to determine whether pFF (inhibin) can act effectively on pituitary FSH secretion in the MSG-lesioned rat. MSG (4 mg/kg B.W.) or saline was injected subcutaneously on postnatal days 2, 4, 6, 8, and 10 to male and female littermates which were used in the experiments after postnatal day 60. In the first experiment male and female littermates were bilaterally gonadectomized and bled serially for the next 72 h. At 0 h plasma FSH concentrations in MSG-treated rats were lower (p less than 0.05) than those in saline-treated controls, and for the 72 h immediately following bilateral gonadectomy FSH levels increased parallel to those of the controls, but after a significant delay. In the second experiment, MSG-treated male and female littermates were injected with 0.5 ml of pFF at several intervals following bilateral gonadectomy and decapitated 6 hours later. Injection of pFF significantly suppressed circulating FSH titers in all groups without affecting LH levels. In a third experiment, rats were unilaterally gonadectomized and blood samples were obtained at various intervals for 48 h. Following unilateral gonadectomy there was a significant transient increase in FSH levels in male or female MSG-treated rats as compared to their 0 h values; however, the absolute levels attained were barely equal to the basal concentrations observed in the saline-treated control rats. The conclusions from these data are: insufficient FSH secretion in response to unilateral gonadectomy may be responsible for the lack of compensatory gonadal hypertrophy in MSG-lesioned rats, pituitary response to inhibin is apparently unaltered by MSG toxicity, and the MSG-lesioned rat is a useful model to study the differential control mechanisms of FSH and LH secretion.     

Effects of gonadotropin-releasing hormone administration on the pituitary-gonadal axis in male and female dogs before and after gonadectomy

GnRH-stimulation tests were performed in 14 female and 14 male client-owned dogs of several breeds, before and 4 to 5 mo after gonadectomy. The aim of the study was to obtain more insight into the pituitary-gonadal axis in intact and neutered dogs and to establish reference values. Basal plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations were increased significantly after gonadectomy in both bitches and male dogs. In both males and females ranges of the basal plasma FSH concentrations, before and after gonadectomy, did not overlap as opposed to the overlap in ranges of the basal plasma LH concentrations. Before gonadectomy basal plasma LH concentrations were lower and basal plasma FSH concentrations were higher in bitches than in male dogs. After gonadectomy these basal values did not differ significantly. GnRH administration before gonadectomy resulted in an increase in plasma LH and FSH concentrations in both genders. GnRH administration after gonadectomy produced an increase only in plasma LH concentrations in both genders, and a just significant increase in plasma FSH in castrated male dogs. GnRH administration before gonadectomy resulted in a significant increase in plasma testosterone concentration in both genders. In males ranges of basal and GnRH-stimulated plasma testosterone concentrations before and after gonadectomy did not overlap. Basal plasma estradiol concentrations were significantly higher in intact males than in castrated males and their ranges did not overlap. The basal estradiol concentrations in bitches before and after ovariectomy were not significantly different. At 120 min after GnRH administration, ranges of plasma estradiol concentration of intact and ovariectomized bitches no longer overlapped. In conclusion, basal plasma FSH concentration appears to be more reliable than basal plasma LH concentration for verification of neuter status in both male and female dogs. The basal plasma testosterone concentration appears to be reliable for verification of neuter status in male dogs. The plasma estradiol concentration at 120 min after GnRH administration can be used to discriminate between bitches with and without functional ovarian tissue.     

Lithium-induced changes in the plasma and pituitary levels of luteinizing hormone,follicle stimulating hormone and prolactin in rats

Adult male Sprague-Dawley rats, maintained under a controlled photoperiod of LD 14:10 (white lights on at 06:00 h, CST), were injected with lithium chloride and changes in the levels of plasma and pituitary homogenates of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) were examined to evaluate the effects of this anti-manic drug on reproductive function. Two groups of rats were injected with lithium chloride intraperitoneally, twice daily at 09:00 and 16:00 h, for 2 and 7 days at a dosage of 2.5 meg/Kg body weight. Plasma and pituitary levels of LH, FSH and PRL were measured by radioimmunoassay. Plasma levels of LH were significantly (P<0.05) increased after 2 days of lithium treatment. In contrast, a significant (P<0.005) reduction in plasma levels of LH was evident when lithium injections were continued for 7 days. The plasma levels of FSH remained unaffected by lithium treatment by either time period. Lithium administered for 2 days did not bring about any significant alteration in the plasma levels of PRL, although there was a significant (P<0.002) reduction in plasma PRL levels after 7 days treatment. The concentrations of pituitary LH, FSH and PRL remained unchanged after 2 and 7 days of lithium treatment.     

Altered sexual development in male rats after oestrogen administration during the neonatal period.

Male rats given 250 mug oestradiol benzoate by subcutaneous injection on Day 4 of postnatal life showed a marked delay in the onset of the pubertal increase in the weight of the testes and seminal vesicles and in spermatogenesis but not a complete failure of sexual development. The increase in plasma testosterone concentration at puberty was also delayed in oestrogen-treated males but the eventual increase in seminal vesicle weight was closely related in time to the delayed increase in plasma testosterone concentration. Both plasma LH and FSH concentrations were reduced for about 10 days after oestrogen administration as compared to control values. After 22 days of age, plasma LH concentration did not differ significantly from the control values. The plasma FSH concentration of the oestrogen-treated males showed a delayed rise to values equal to or higher than those of controls of the same age. The delayed rise in plasma FSH concentration in the oestrogen treated males preceded the delayed rise in plasma testosterone in these animals. The decrease in plasma FSH concentration from the high prepubertal values to the lower values in adults occurred at different ages in the control and in oestrogen-treated rats but in both groups the decrease occurred as plasma testosterone levels were increasing and the first wave of spermatogenesis was reaching completion. The increase in plasma FSH concentration after castration was reduced in oestrogen-treated males during the period throughout which FSH levels in the intact animals were subnormal but the levels in oestrogen-treated males castrated after the delayed rise in FSH had occurred did not differ from control values. It is suggested that the delayed sexual maturation of male rats treated with high doses of oestrogen in the neonatal period is related principally to abnormalities in the secretion of FSH.     

Study of testicular feedback in male rats using artificial cryptorchidism as a model.

Plasma LH, FSH and testosterone were measured in testosterone-treated and untreated cryptorchid and castrated male rats. Exogenous testosterone prevented the increase in basal LH but not FSH levels seen in the untreated cryptorchids. Increases in plasma LH and FSH in response to LH-RH were greater in the cryptorchid as compared to the control group and this could not be reversed by exogenous testosterone, suggesting that spermatogenesis-related feedback factors regulate LH as well as FSH at the pituitary level in the intact rat. The results were consistent with a reduced but nevertheless significant secretion of inhibin by the cryptorchid testis. Basal plasma testosterone levels and ventral prostate weights were not significantly different from intact animals.     

Effects of luteinizing hormone on superovulatory and steroidogenic responses of rat ovaries to infusion with follicle-stimulating hormone

Immature female rats were infused s.c. continuously over a 60-h period with a partially purified porcine pituitary follicle-stimulating hormone (FSH) preparation having FSH activity 4.2 x NIH-FSH-S1 and luteinizing hormone (LH) activity 0.022 x NIH-LH-S1. High rates of superovulation were observed in rats receiving 1 U FSH/day, with 69 +/- 11 oocytes/rat recovered as cumulus-enclosed oocytes from oviducts on Day 1 (equivalent to the day of estrus). Addition of LH to the FSH, at dosages equivalent to 2.5-100 micrograms/day NIH-LH-S1 equivalents (2.5-100 mU) resulted in a dose-related inhibition of superovulation, reaching a nadir of 15 +/- 7 oocytes recovered from rats receiving 50 mU LH/day together with 1 U FSH/day. At the two highest LH doses, 50 and 100 mU/day, ovulation was advanced so that 12 +/- 3 and 15 +/- 4 oocytes, respectively, were recovered from oviducts of these rats flushed on the morning of Day 0, compared to none in rats infused with FSH alone. Ovarian steroid concentrations (ng/mg) observed on the morning of Day 0 in rats infused with FSH alone were progesterone, 0.50 +/- 0.13; testosterone, 0.16 +/- 0.08; androstenedione, 0.06; and estradiol, 0.23 +/- 0.05. On the morning of Day 1, ovarian progesterone concentrations in rats infused with FSH alone had risen to 3.30 +/- 0.33 ng/mg, whereas concentrations of testosterone, androstenedione, and estradiol, had fallen to essentially undetectable levels. Addition of LH to the FSH infusion resulted in dose-related increases, on Day 0, of all four steroids up to a dosage of 25 mU LH/day. At higher LH dosages, Day 0 ovarian concentrations of androgens and estradiol fell markedly, while progesterone concentrations continued to increase. Histological examination of ovaries revealed increases in the extent of luteinization of granulosa cells in follicles with retained oocytes on both Days 0 and 1 in rats infused with 25 and 50 mU LH/day together with 1 U FSH/day, compared to those observed in rats receiving FSH alone. These findings indicate that the elevated progesterone levels on Day 0 and inhibition of ovulation observed at these LH doses were due to premature luteinization of follicles, thus preventing ovulation. At lower LH doses, no sign (based on histologic or steroidogenic criteria) of premature luteinization was evident, suggesting that the decreased superovulation in these rats was due to decreased follicular maturation and/or increased atresia rather than to luteinization of follicles without ovulation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Short-term effects of vasoligation upon plasma follicle-stimulating hormone, luteinizing hormone, and prolactin in the adult rat: further evidence for a direct neural connection between the testes and the central nervous system

The purpose of these experiments was to determine whether bilateral vasoligation of adult male rats had any short-term effects upon plasma levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin. Adult male rats (250-300 g) were either bilaterally vasoligated or sham vasoligated, and blood samples were obtained by cardiac puncture preoperatively and at 24 h and 7 days following surgery. Plasma levels of both FSH and LH were significantly (P less than 0.01) decreased at 24 h following vasoligation compared to preoperative levels and those of sham-operated controls. However, the response was differential since, at 7 days following vasoligation, plasma FSH was still significantly decreased while LH was returning to control levels. Conversely, plasma prolactin levels were significantly (P less than 0.01) increased at 24 h compared to preoperative values and those in sham-operated controls, and at 7 days prolactin had returned to preoperative control levels. Sham vasoligation did not significantly change plasma levels of FSH, LH, or prolactin at any of the time intervals investigated. These results provide further evidence that suggests that there may be a direct connection between the testis and central nervous system that may be involved in the short-term regulation of gonadotropin and prolactin secretion.