Somatostatin affects morphology and secretion of pituitary luteinizing hormone (LH) cells in male rats

The somatostatin peptides (SRIH-14, SRIH-28) and their multiple receptors are generally associated with anti-proliferative and anti-secretory actions. This study compared, using standard morphometric measurements and terminal serum LH concentrations, effects of intracerebroventricular (icv) SRIH-14 and SRIH-28 in nanomolar amounts on immunohistochemically identified LH cells in pituitary glands of male rats. Rats received l microg/5 microl of SRIH-14 or SRIH-28 icv on days 1,3, and 5, whereas control rats received only icv saline. Animals were killed 5 days later for serum LH assays. Pituitarys were harvested for PAP immunohistochemistry and morphometry. Morphometric measurements were made by an observer blinded to the treatment group. Histochemically identified LH cells from both SRIH groups appeared smaller, often pycnotic and darkly stained compared to those from saline-treated rats. Both SRIH treatments reduced (p < 0.05) the quantitative morphometric measurements for cell volume, nuclear volume, and relative volume density. Both SRIH treatments also reduced serum LH concentration (p < 0.05), supporting the hypothesis that systemic physiology was altered. Collectively, the data support the opinion that nanomolar amounts of either SRIH peptide, acting on receptors reached from cerebrospinal fluid, exert an anti-secretory effect on LH cells of male rats. Modifications of central SRIH receptors may provide an approach for treatment of male sexual dysfunction and/or be of pathophysiologic significance in these disturbances.     

The effects of chronic SRIH-14 and octreotide administration on the pituitary-adrenal axis in adult male rats

The effects of chronic treatments with SRIH-14 and octreotide on pituitary corticotropes (ACTH cells) and on the adrenal cortex of male Wistar rats were examined. Adult males received two daily s.c. injections of 20 microg/100 g of body weight of either SRIH-14 or octreotide for 28 consecutive days. ACTH cells were studied using a peroxidase-antiperoxidase immunocytochemical procedure. Morpho-metry was used to evaluate the changes in cell and nuclear volumes (microm3) and volume densities (%) of ACTH-immunoreactive cells. The adrenal cortex was analyzed by histological and morphometric methods. A significant (p<0.05) decrease in body weight and in the absolute weights of the pituitary and adrenal glands was observed in both treated groups. Morphometric parameters of ACTH cells in both treated groups were not significantly (p>0.05) different than in control rats. The absolute volumes of the adrenal gland and adrenal cortex were significantly (p<0.05) decreased in both treated groups. The absolute and relative volumes of the zona glomerulosa (ZG), as well as the cellular and nuclear volumes of the ZG were significantly (p<0.05) decreased in the both treated groups. In rats treated with SRIH-14 and octreotide, the absolute and relative volumes of the zona fasciculata (ZF) and zona reticularis (ZR), as well as their stereological parameters, did not change significantly (p>0.05). The aldosterone levels in the SRIH-14 and ocreotide-treated groups were significantly (p<0.05) decreased - by 13% and 19%, respectively. The concentration of ACTH and corticosterone did not change significantly. Together, these findings show that SRIH-14 and octreotide administration affected the morphological characteristics of the adrenal ZG in a similar manner, and brought about a decrease in plasma aldosterone concentration. These treatments did not affect pituitary ACTH cells or adrenal ZF and ZR functioning.     

Effect of centrally administered somatostatin on pituitary thyrotropes in male rats

The effects of intracerebroventricularly administered somatostatin (SRIH-14 or -28) on growth and function of pituitary thyrotropes (TSH-cells) were examined in adult male Wistar rats. The animals were implanted with an intracerebroventricular cannula and after a recovery period, administered three 1g doses of SRIH-14 or -28 dissolved in 5l saline every second day. Controls were treated in the same way with the same volume of saline only. TSH-producing cells were studied using the peroxidase–antiperoxidase immunohistochemical procedure. Blood samples were collected for hormone (TSH) analyses 5 days after the last injection. Both SRIH-treatments significantly decreased (p < 0.05) all morphometric parameters obtained for TSH-cells in comparison with controls. The volume of TSH-cells decreased by 27%, nuclei by 44% and volume density by 33% in animals treated with SRIH-14. In animals treated with SRIH-28, these parameters were also significantly decreased (p < 0.05) (22%, 31%, and 25% respectively) compared to control rats. Serum concentrations of TSH were significantly decreased (p < 0.05) by 15% in SRIH-14- and by 12% in SRIH-28-treated animals in comparison with the controls. These observations suggest that centrally administered SRIH-14 or -28 is specifically involved in the control of growth and secretory activity of TSH cells.     

Somatostatin 14 affects the pituitary-ovarian axis in infant rats

The effects of multiple somatostatin (SRIH-14) treatment on the pituitary-ovarian axis were examined in infant rats. Female Wistar rats received subcutaneously two daily 20 μg/100g b.w. doses for five consecutive days (from 11 to 15 days of age). Changes in cell volume, volume density and number per unit area (mm2) of follicle-stimulating (FSH), luteinizing (LH) and somatotropic (GH) immunolabeled cells were evaluated by stereology and morphometry. Serum FSH and LH concentrations were determined by RIA. Ovaries were analyzed by simple point counting of follicles. SRIH-14 treatment significantly reduced FSH and LH cell volume, while their volume density and number per unit area were unaltered. Serum concentrations of FSH and LH were significantly reduced. Volume and volume density of GH cells was significantly decreased after SRIH-14 treatment, while their number per unit area was unaltered. In the ovary, SRIH-14 induced a significant increase in the percentage of primordial follicles followed by a significant decrease in percentage of primary follicles. The number of healthy and atretic preantral follicles was unchanged. It can be concluded that SRIH-14 treatment during the infantile period markedly inhibits pituitary FSH, LH and GH cells. In the ovary, SRIH-14 acts by inhibiting initial folliculogenesis without affecting atretic processes.     

Somatostatin-14 influences pituitary–ovarian axis in peripubertal rats

The effects of multiple somatostatin (SRIH-14) administration on the pituitary-ovarian axis were examined in peripubertal rats. Female Wistar rats received subcutaneously, two daily doses of 20 mug SRIH-14 per 100 g body weight (b.w.) for five consecutive days (from the 33rd to the 37th day of life). Follicle-stimulating (FSH), luteinizing (LH) and somatotropic (GH) cells were examined by the peroxidase-anti-peroxidase immunocytochemical method. Changes in cell volumes, volume densities and number per unit area (mm(2)) of FSH-, LH- and GH-immunoreactive cells were evaluated by stereology and morphometry. Serum FSH and LH levels were determined by RIA. Ovaries were analyzed by simple point counting of follicles. The volumes and volume densities of FSH-, LH- and GH-immunoreactive cells were significantly decreased while their numbers per mm(2) remained unchanged. SRIH-14 induced a significant decrease in serum FSH and LH levels. In the ovary, SRIH-14 induced an increase in the number of primordial follicles, followed by a reduction in the number of small healthy growing follicles and absence of preovulatory follicles. The number of atretic follicles was unchanged. We concluded that treatment with SRIH-14 during the peripubertal period markedly inhibited pituitary FSH, LH and GH cells. In the ovary, SRIH-14 acted by inhibiting folliculogenesis without affecting atretic processes.     

Chronic somatostatin treatment affects pituitary gonadotrophs, ovaries and onset of puberty in rats

The effects of chronic somatostatin (SRIH-14) treatment on the pituitary gonadotrophs (FSH and LH cells) and ovaries of female Wistar rats were examined. Females were given 20 microg/100 g b.w. twice per day from the immature (23rd day) till the adult period of life (71st day). The onset of puberty was determined by daily examination for vaginal opening. The peroxidase-antiperoxidase immunocytochemical procedure was used to study the gonadotrophs. Changes in the number per unit area (mm2), cell volume and volume densities of LH- and FSH-immunoreactive cells were evaluated by morphometry and stereology. Ovaries were analysed by simple point counting of follicles and corpora lutea (CL). Follicles were divided by size according to the classification of Gaytán and Osman. The mitotic indexes of granulosa and theca cells in the follicles were estimated at all stages of folliculogenesis. The number, volume and the volume density of FSH- and LH-immunoreactive cells decreased after chronic SRIH-14 treatment, particularly the latter. In the ovary, SRIH-14 treatment decreased the number of healthy follicles at all phases of folliculogenesis, lowered the mitotic indexes of granulosa and theca cells but increased the number of atretic follicles. Healthy CL were fewer in number, while regressive CL were increased. Vaginal opening occurred at a later age in treated females. It can be concluded that chronic SRIH-14 treatment markedly inhibited LH cells and to a lesser extent FSH cells. In the ovary SRIH-14 inhibited folliculogenesis, enhanced atretic processes and lowered proliferative activity of granulosa and theca cells. It also delayed puberty onset.     

Effects of multiple somatostatin treatment on rat gonadotrophic cells and ovaries

The effect of multiple somatostatin (SRIH-14) treatment on the pituitary gonadotrophs, follicle stimulating harmone (FSH) and luteinizing harmone (LH), and ovaries of adult female Wistar rats was examined. Females received two 20 microg/100 g body wt. doses daily subcutaneously, for five consecutive days. FSH and LH cells were studied using a peroxidase-antiperoxidase immunocytochemical procedure. Morphometry and stereology were used to evaluate changes in the number per unit area (mm2), cell volume and volume densities of LH- and FSH-immunoreactive cells. Ovaries were analysed by simple point counting of follicles and corpora lutea. Follicles were divided by size according to the classification of Gaytán and Osman. Morphometric and stereological analysis of the pituitary showed that the number, volume and the volume density of FSH- and LH-immunoreactive cells were decreased after multiple SRIH-14 treatment, particularly in the latter. In the ovary, SRIH-14 induced decreases in the number of healthy follicles in all phases of folliculogenesis and corpora lutea, but the large antral follicle stage was most affected. The number of atretic follicles was increased. It can be concluded that multiple SRIH-14 treatment markedly inhibited LH cells, but affected FSH cells as well. In the ovary, SRIH- 14 acted by inhibiting folliculogenesis and enhancing atretic processes.     

Effect of gonadectomy and steroid treatment on the receptor-binding activity and immunoreactivity of serum and pituitary FSH in the adult rats of both sexes

The receptor binding activity (R) and immunoreactivity (I) of serum and pituitary FSH were measured in normal, gonadectomized, and gonadal steroid-treated rats of both sexes employing radioreceptor assay and radioimmunoassay, respectively, and R/I ratios were analyzed. At 11 weeks of age, R/I ratios of serum and pituitary FSH were significantly higher in normal females than in males. From 11 to 13 weeks of age, the ratios of both FSH further increased in females, while in males, the ratio of serum FSH decreased and that of pituitary FSH increased. Orchiectomy caused an increase in the ratio of serum FSH, while ovariectomy caused a decrease, so the ratios in the gonadectomized animals of both sexes became almost equal, suggesting the secretion of a gonadectomy type FSH in these animals. Both testosterone propionate (TP) and estradiol benzoate (EB) treatments decreased the ratios of serum FSH in gonadectomized rats. However, TP and EB had an effect opposite on the ratio of pituitary FSH in these rats, i.e. TP caused a decrease, while EB caused an increase. This effect was more obvious in females than in males. These observations indicated that the presence and absence of the gonads, and the gonadal steroids influence not only the quantity but also the quality of FSH. The changes in the quality of the hormone are discussed in relation to its multiplicity.     

Inhibitory control of the pituitary LH secretion by LH-RH in male rats.

Luteinizing hormone-releasing hormone (LH-RH) was administered to prepubertal male rats (intact, castrate or castrate-adrenalectomized, 60 g body weight) for 28 days (1 microgram LH-RH/day, s.c.), at a 10-fold physiological dose, as compared to the minimal FSH-releasing dose of 100 ng/rat s.c. In intact rats, serum LH and weight of androgen-dependent organs (vented prostate, seminal vesicles) were reduced after 14 days of treatment. In castrate rats, the postcastration rise in serum LH was abolished by treatment. Pituitary LH content, FSH secretion and prolactin secretion were not suppressed. Hypothalamic LH-RH was increased at 14 and 21 days. In castrate adrenalectomized male rats, LH secretion was also suppressed by 1 microgram LH-RH s.c. x 28 days. The hypothalamic LH-RH content did not increase. The pituitary LH-RH receptor level was not down-regulated after 14 days treatment either in intact or castrate male rats. Pituitary inhibition (LH release) in rats by a supraphysiological dose of LH-RH given for 28 days indicates that the optimal regime for chronic treatment has to be determined by monitoring LH release at regular intervals. Direct pituitary inhibition by LH-RH may explain some of the unexpected antifertility effects observed with high doses of LH-RH.     

Testosterone selectively increases serum follicle-stimulating hormonal (FSH) but not luteinizing hormone (LH) in gonadotropin-releasing hormone antagonist-treated male rats: evidence for differential regulation of LH and FSH secretion

Both testosterone (T) and gonadotropin-releasing hormone (GnRH)-antagonist (GnRH-A) when given alone lower serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in intact and castrated rats. However, when graded doses of testosterone enanthate (T.E.) were given to GnRH-A-treated intact male rats, a paradoxical dose-dependent increase in serum FSH occurred; whereas serum LH remained suppressed. This surprising finding led us to ask whether the paradoxical increase in serum FSH in GnRH-A-suppressed animals was a direct stimulatory effect of T on the hypothalamic-pituitary axis or the result of a T effect on a testicular regulator of FSH. To test these hypotheses, we treated adult male castrated rats with GnRH-A and graded doses of T.E. In both intact and castrated rats, serum LH remained undetectable in GnRH-A-treated rats with or without T.E. However, addition of T.E. to GnRH-A led to a dose-dependent increase in serum FSH in castrated animals as well, thus pointing against mediation by a selective testicular regulator of FSH. These data provide evidence that pituitary LH and FSH responses may be differentially regulated under certain conditions. When the action of GnRH is blocked (such as in GnRH-A-treated animals), T directly and selectively increases pituitary FSH secretion.     

Breed differences in clearance of porcine FSH in hypophysectomized rats

Extracts of anterior pituitary (AP) glands were infused i.v. into hypophysectomized male rats followed by sequential sampling of blood for 120 min. Determination of follicle-stimulating hormone (FSH) concentrations established that FSH from Chinese Meishan males decreased in the circulation of rats more slowly than FSH in extracts of AP from crossbred occidental pigs (P<0.003). Additionally, FSH from AP extracts of castrated males disappeared somewhat more slowly (P<0.06) than FSH from extracts of boars. Evaluation of FSH by bioassay and radioimmunoassay yielded similar concentrations in AP from Meishan and crossbred boars. Serum testosterone concentrations increased with time through 90 min after infusion of AP, but the rate of increase of testosterone was not related to amount of luteinizing hormone (LH) that was administered indicating LH receptor saturation. Unexpectedly, the rate of increase in testosterone was more rapid with AP extracts from boars than with extracts from castrated males. Observations from the current study imply structural alterations of FSH in the AP of Meishan males relative to crossbred males allowing sustained concentrations in the circulation, and this FSH possesses similar activation of the FSH receptor. The amount of LH in the AP extracts saturated the LH receptors of the hypophysectomized male rats, but some factor in extracts of boars differed from those of castrated males.     

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.     

Morphological changes to somatotroph cells and in vitro individual GH release, in male rats treated with recombinant human GH

The effect of in vivo chronic administration of recombinant human growth hormone (rhGH) on morphology and individual GH release in somatotroph cells was evaluated in young male Wistar rats. Over an 18-day period, 30-day-old male rats were injected daily with 1.5 1U rhGH/kg (GPG group) or saline (VPG group) by subcutaneous injection. Electron-immunocytochemical, ultrastructural and morphometric studies of somatotroph cells were carried out. Additionally, rat pituitary cells were dispersed and overall and individual GH release was studied by radioimmunoassay and cell immunoblot assay (quantified by image analysis), respectively. The ultrastructure and size of somatotroph cells did not change, but volume density of secretion granules was reduced (p<0.01) by previous in vivo GH treatment. At four days, basal GH release of rat pituitary cell monolayer cultures was lower in the GPG group than in the VPG group (p<0.05); after 12 hours of culture, GHRH stimulation of GH release was lower in the GPG group than in the VPG group (p<0.05), and GHRH+SRIH inhibited GH release in the GPG group (p<0.05), but not in the VPG group. The percentage of somatotroph cells was not modified, but the ratio of strongly/weakly GH-immunostained cells had changed; weakly GH-immunostained cells increased from 34% to 55%. Moreover, in vitro treatment with GHRH, SRIH, and both, easily changed the strongly/weakly GH-immunostained cell ratio. Individual GH release, however, was not changed by previous in vivo GH treatment, although GHRH preferably stimulated a subpopulation of GH cells and SRIH did not inhibit individual GH release. These data suggest that exogenous chronic rhGH treatment down-regulates somatotroph function by modifying the proportion of GH cell subpopulation.     

Inhibition of pituitary bioactive prolactin secretion in the male rat by the glucocorticoid agonist decadron phosphate.

In the present studies, the soluble glucocorticoid agonist, decadron phosphate (DEC), was administered i.v. to intact adult male rats in order to evaluate the effects of glucocorticoid receptor stimulation on circulating levels of immunoreactive (ir-) and bioactive (bio-) prolactin (PRL). In light of reports that glucocorticoid-specific receptors exist within the rat brain, additional experiments investigated the effects of intracerebroventricular (i.c.v.) administration of graded doses of the same drug on pituitary ir- and bioPRL secretion. Concentrations of ir- and bioPRL in samples obtained before and after drug treatments were determined by standard PRL radioimmunoassay and the Nb2 rat node lymphoma bioassay, respectively. Rats injected i.v. with 0.5 mg DEC/kg body weight, but not those treated with a tenfold lesser dose, exhibited decreased plasma irPRL concentrations. However, both doses promoted a decline in circulating levels of bioPRL compared to vehicle-treated controls, along with an overall reduction in the plasma bio/irPRL ratio. The magnitude and duration of this drug-induced decline in biopotency of secreted hormone was dose-dependent. While the plasma bio/irPRL ratio was diminished only transiently in rats injected with 0.05 mg DEC/kg, treatment with the higher dose led to a sustained decrease in the plasma bio/irPRL ratio for the duration of the experiment. The current studies also show that intracerebral administration of DEC resulted in dose-dependent alterations in pituitary PRL release. Circulating levels of ir- and bioPRL were not altered in rats injected i.c.v. with 10 ng of DEC, the lowest dose tested.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dexamethasone increases inhibin and estradiol secretion mediated by endogenous FSH in equine chorionic gonadotropin (eCG)-primed immature female rats.

In the present study, we have examined whether the effects of dexamethasone on follicle stimulating hormone (FSH) secretion were mediated by hypophysiotropic factors, and whether the increased levels of FSH induced by dexamethasone can stimulate ovarian functions in equine chorionic gonadotropin (eCG)-primed immature female rats. Dexamethasone (500 microg) significantly increased serum concentrations of FSH in hypophysectomized rats implanted with pituitary under the kidney capsule, as well as in intact rats. Serum concentrations of inhibin and estradiol in eCG (2.5, 5 i.u.)-primed rats were significantly increased by simultaneous treatment with dexamethasone (500 microg) and eCG. These simultaneous effects were not confirmed in hypophysectomized rats. The results had shown that hypophysiotropic factors do not mediate the selective increase of FSH secretion caused by dexamethasone. Dexamethasone induces the excess amount of FSH secretion from anterior pituitary and this FSH can stimulate inhibin and estradiol secretion in eCG-primed immature female rat.     

Stimulatory effect of Sertoli cell culture medium on the FSH release by pituitary halves in vitro

The influence of the medium collected from cultured rat Sertoli cells on the spontaneous and LHRH-stimulated release of gonadotropins by incubated rat pituitary halves was examined. The homogeneity of the cultured population of Sertoli cells taken from 20-day-old rats ranged up to 98%. The cells in culture responded to FSH stimulation with characteristic morphological changes and with increased secretion of estradiol-17 beta. The hemi-pituitaries obtained from sexually mature male rats were incubated for 5 hours in the presence of Sertoli cell culture medium (SCCM) or its fractions obtained by use of ultrafiltration. The SCCM fraction deprived of MW less than 10 kD compounds exhibited a typical inhibin-like activity, whereas crude SCCM as well as its low-molecular-weight fraction stimulated the basal FSH release to about 150% and 175% of the control values, respectively. These fractions exerted an inhibitory effect on the LHRH-stimulated secretion of both LH and FSH. It is concluded that Sertoli cells cultured in chemically defined medium release, apart from inhibin, a non-steroidal, heat-labile substance of MW less than 10 kD which stimulates the basal secretion of FSH and LH and inhibits the LHRH-stimulated secretion of both gonadotropins from incubated rat hemi-pituitaries.     

Feedback control of FSH secretion in the male rat

Site of feedback control of FSH secretion in the male rat was studied by measuring changes in serum LH, FSH and hypothalamic LH-RH by radioimmunoassay in rats after castration and after 500 rad X-irradiation to the testis. The rise in serum LH and FSH in castrated animals was associated with a significant fall in hypothalamic LH-RH 16 and 24 days after castration. Serum FSH rose significantly after X-irradiation without a significant change in serum LH or hypothalamic LH-RH content up to 30 days after irradiation. When pituitary halves from X-irradiated animals were incubated in vitro in the presence or absence of synthetic LH-RH, there was a significant rise in FSH (but not LH) released in the incubation medium in the absence of added LH-RH. The response of the pituitaries to LH-RH was, however, not different between control and irradiated rats. It is concluded that the testicular FSH-inhibitory substance acts predominantly at the pituitary gland on the LH-RH independent release of FSH.     

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.     

Blockade of pulsatile LH, FSH and testosterone secretion in rams by constant infusion of an LHRH agonist

Adult Soay rams were infused for 21 days with 50 micrograms buserelin/day, using s.c. implanted osmotic mini-pumps. The continuous treatment with this LHRH agonist induced a supraphysiological increase in the blood concentrations of LH (15-fold) and testosterone (5-fold) followed by a decrease below pre-treatment values after 10 days. The blood concentrations of FSH showed only a minimal initial increase but the subsequent decrease was dramatic, occurring within 1 day. By Day 10 of treatment, the blood concentrations of all 3 hormones were low or declining, LH pulses were absent in the serial profiles based on 20-min blood samples and the administration of LHRH antiserum failed to affect the secretion of LH or testosterone. By Day 21, the secretion of FSH, LH and testosterone was maximally suppressed. The i.v. injection of 400 ng LHRH was totally ineffective at stimulating an increase in the blood concentrations of LH while the i.v. injection of 50 micrograms ovine LH induced a normal increase in the concentrations of testosterone; this confirmed that the chronic treatment with the LHRH agonist had desensitized the pituitary gonadotrophs without markedly affecting the responsiveness of the testicular Leydig cells. The ratio of bioactive: radioimmunoactive LH did not change during the treatment. The long-term effect of the infusion was fully reversible as shown by the increase in the blood concentrations of FSH, LH and testosterone and the return of normal pulsatile fluctuations in LH and testosterone within 7 days of the end of treatment.     

Multiple dexamethasone treatment affects morphometric parameters of gonadotrophic cells in adult female rats

Exposure to glucocorticoids leads to numerous changes in various biological systems including the reproductive system. The aim of the present work was to find out whether dexamethasone (Dx) treatment of adult female rats would influence the histological and morphometric characteristics of the pituitary gonadotrophic cells (luteinizing--LH cells and follicle stimulating--FSH cells). One group of female Wistar rats received Dx injections on three consecutive days in doses 1.0, 0.5 and 0.5 mg/kg b.w. respectively, while the control rats were treated with equivalent volumes of saline. Experimental and control animals were sacrificed 24 h and 72 h after the last injection. The peroxidase-antiperoxidase (PAP) immunocytochemical procedure was used to study the LH and FSH cells. The stereological and morphometric analyses showed that multiple Dx treatments of female rats significantly decreased the volume of LH cells and the volume of their nuclei 24 h and 72 h after the last Dx injection in comparison with control values. At 24 h after Dx treatment, the volume density of LH cells was significantly increased, but at 72 h differences between the experimental and control groups were insignificant. The increase in number of LH cells per unit area (mm2) was significant at both timepoints (24 h and 72 h). Stereologic and morphometric characteristics of FSH cells was changed after Dx treatment in the same manner as that of LH cells, except for the volume density, where a significant increase was established 24 h and 72 h after the last Dx application. These results clearly demonstrate that 24 h and 72 h after the last of three Dx injections there were changes in the immunocytochemical and morphometric features of gonadotrophic cells.