Neonatal estrogen affects preoptic/anterior hypothalamic LHRH differently in adult male and female rats

When administered during the critical perinatal period, estrogen permanently modifies both male and female reproductive function. This study evaluated the influence of exogenous estrogen administered during this time on the hypothalamic LHRH content and on gonadotropin secretion in adult male and female rats. LHRH content in the preoptic-anterior hypothalamic (PO/AH) and midhypothalamic (MH) areas of neonatally estrogenized rats (1 mg on postpartum day 2) and of control male and female rats during the estrous cycle was determined by radioimmunoassay between 80 and 90 days of age. LHRH content was significantly greater in the PO/AH of neonatally estrogenized females than in estrogenized males whereas no differences in LHRH content of the PO/AH existed between control male and female rats. Neonatal administration of estrogen resulted in increased LHRH content in the MH of female rats and decreased LHRH content in male rats, as in the PO/AH; however, these differences were less marked in the MH and not statistically significant. The marked increase in serum LH concentration present in control cycling females in proestrus was abolished by neonatal estrogen treatment. Exposure to neonatal estrogen reduced FSH concentrations in males. The data are consistent with the concept that the hypothalamic-pituitary system is modified by estrogen circulating during the period of sexual differentiation. LHRH synthesis and release appear to be directly modified by neonatal estrogen. The effects of neonatal estrogen treatment in the PO/AH and MH areas may possibly involve two disparate types of alterations of developing LHRH neurons which modulate gonadotropin secretion in the adult rat.     

Immunoreactive prolactin in the hypothalamus and cerebrospinal fluid of male and female rats

Immunoreactive prolactin (ir-PRL) has been identified in the cerebrospinal fluid (CSF) and brain of the male and female rat. In this study we determined the concentration of ir-PRL in the CSF and hypothalamus under conditions known to increase or decrease serum PRL. Hypophysectomy (60 days) significantly decreased the concentration of ir-PRL in the CSF of male (4.9 +/- 0.7 vs. 3.0 +/- 0.3 ng/ml) and female (5.8 +/- 0.9 vs. 3.1 +/- 0.5 ng/ml) rats. However, the effect of long-term hypophysectomy on hypothalamic ir-PRL was gender-dependent. That is, in the male rat hypophysectomy did not affect the content of ir-PRL in the female rat, long-term hypophysectomy decreased the content of ir-PRL in the median eminence, ventral hypothalamus, and dorsal hypothalamus 37, 40, and 47%, respectively. Estradiol replacement to the hypophysectomized female rat normalized the content of ir-PRL in the median eminence (96 +/- 5.8 to 131 +/- 9.6 ng/mg protein), ventral hypothalamus (11 +/- 0.6 to 16.0 +/- 1.1 ng/mg protein), dorsal hypothalamus (4.7 +/- 0.4 to 8.6 +/- 0.4 ng/mg protein), and the concentration ir-PRL in the CSF (2.5 +/- 0.3 to 4.6 +/- 0.4 ng/ml). In intact female rats, administration of haloperidol induced a marked hyperprolactinemia, and significantly increased CSF ir-PRL (5.1 +/- 1.5 vs. 18.0 +/- 3.8 ng/ml). However, in the same rats, the content of ir-PRL in the median eminence was significantly decreased while the ir-PRL content in the ventral hypothalamus and dorsal hypothalamus was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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.     

Aromatization of androstenedione by microsomes from the human placenta after gestational alcohol consumption

Human placental microsomes were used to evaluate rates of andre stenedione aromatiration from patients selected for gestational alcohol consumption. After term delivery, kinetic comparisons of specific activity and Michaelis constants of reduced pyridine nucleotide cotactors were determined. The data failed to indicate a significant alcohol effect on these enzymatic parameters.     

Indoleamines in the hypothalamus and area of the midbrain raphe nuclei of male and female rats throughout postnatal development

We have investigated the changes in the concentrations of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in the hypothalamus-preoptic area (HPOA) and midbrain raphe (MR) region of male and female rats throughout development. No sex differences were found in the concentrations of the indoleamines in either of the areas investigated at any stage of development. The 5-HIAA/5-HT molar ratio was maximal at 4 days of age in both the HPOA and MR. A small but significant sex difference in the 5-HIAA/5-HT ratio occurred in the HPOA (higher in males) but not in the MR at 40 days of age, and the ratio was significantly greater in 80-day-old female rats in the HPOA but not MR. Studies using NSD 1015 to block the conversion of 5-hydroxytryptophan to 5-HT showed that a higher rate of 5-HT synthesis occurred in the HPOA of 80-day-old rats compared with the neonatal HPOA and that in 80-day-old rats the rate of 5-HT synthesis was significantly higher in females. These results show that endogenous steroids do not affect the activity of serotoninergic neurons in the HPOA or MR either during or immediately after the critical period of sexual differentiation. In addition, the results from the NSD 1015 experiments show that the high 5-HIAA/5-HT ratio found in neonates does not involve a higher rate of 5-HT synthesis than that in adult rats.     

A comparative study of the effects of neonatal androgenization and estrogenization on vasoactive intestinal peptide levels in the anterior pituitary and the hypothalamus of adult female rats.

We compared the effects of neonatal androgenization (NA) and estrogenization (NE) on vasoactive intestinal peptide (VIP) levels in the anterior pituitary (AP) and the hypothalamus and on prolactin (PRL) secretion in adult female rats. Twenty-four hours after birth, a total of seven groups were treated as follows. Three NA groups received a single subcutaneous injection of 10, 100, or 1,000 micrograms of testosterone, respectively. Similarly, three NE groups received 1, 10, or 100 micrograms of 17 beta-estradiol, respectively. The remaining one group was injected with oil vehicle only, and served as controls. At 8 weeks of age, animals were sacrificed by rapid decapitation. NA (1,000 micrograms) and NE (100 micrograms) resulted in a similar degree of hyperprolactinemia and hyperestrogenemia, but this effect ratio between NA and NE (about 1:10) was not true with the lower doses, indicating a qualitative difference in the effects of the two treatments. This is in agreement with our previous study. VIP content determined in the suprachiasmatic nucleus, the paraventricular nucleus and the median eminence did not significantly correlate with plasma PRL. In contrast, there were significant correlations among AP VIP, plasma PRL and estradiol. These results suggest the possibility that the NA- and NE-induced hyperprolactinemia may be mediated, at least in part, by a paracrine and/or autocrine effect of the increased AP VIP on the lactotroph which may probably be mediated by hyperestrogenemia. However, the possibility was also suggested that the observed changes in AP VIP were related more to NA and NE's imprinting effects on the developing brain than to the PRL secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fasting reduces the kiss1 mRNA levels in the caudal hypothalamus of gonadally intact adult female rats

Kisspeptin, which is the product of the kiss1 gene and its receptor kiss1r, have emerged as the essential gatekeepers of reproduction. The present study used gonadally intact female rats to evaluate fasting-induced suppression of the KiSS-1 system of anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC) under normal physiological conditions. Starting on the day of estrous, one group of rats was subjected to 72 h of food deprivation, while the other group of rats was able to continue feeding ad libitum. The length of the estrous cycle was significantly longer in the food-deprived rats as compared to the feeding rats. At the end of the 72-h food deprivation period, all of the food-deprived rats were at the diestrous phase, with their serum concentrations of LH and leptin significantly lower than that observed in the feeding rats. In addition, as compared to the feeding rats, the expression levels of kiss1 mRNA were significantly lower in the food-deprived rats in the posterior hypothalamic block, which contained the ARC, but not in the anterior hypothalamic block, which contain the AVPV. However, both the kiss1r mRNA expression levels in the anterior and posterior hypothalamic blocks and the neurokinin B and neurokinin 3 receptor mRNA expression levels in the posterior hypothalamic block were not significantly different between the feeding and food-deprived rats. Thus, lower kiss1 mRNA levels in the ARC appear to be responsible for the fasting-induced inhibition of gonadotrophin secretion and subsequent prolongation of the estrous cycle.     

Diurnal variations of plasma and pituitary thyrotrophin in adult male and female rats.

Male and female rats fed a low iodine diet for 20 days were used to study the diurnal variations in resting levels of plasma and pituitary TSH concentration using a highly sensitive radioimmunoassay. Sex differences in the fluctuations in plasma TSH levels and in amount of TSH in the pituitary gland were observed. The daily fluctuations of plasma TSH were characterized by two peaks that occurred in males at 6 a.m. and at 3 p.m. while in females the peaks were delayed until 9 a.m. and 7:30 p.m. Moreover, in the females the morning and the afternoon peaks were of the same intensity while in the males the afternoon peak that occurred just before the onset of darkness was much greater than the morning peak. There was a fall in TSH content of the pituitary in the male rats at 6 a.m. and also in the afternoon just before the onset of darkness. Thus, the diurnal variations in the plasma and pituitary TSH levels were related in male rats. In the females, however, the pituitary TSH concentration did not reflect the changes observed in the plasma TSH levels. The level of plasma PBI did not appear to be responsible for the fluctuations in plasma TSH concentration. It is suggested that the main mechanism for the control of the circadian rhythm of TSH might be related to a high activity at night.     

Progesterone induced modulations of serum hormonal profiles in adult male and female rats.

The impact of progesterone on serum hormonal profiles in the presence and absence of gonads was studied in adult male and female albino rats. Progesterone was administered intramuscularly for 30 days at a dose of 1 mg/100g body weight/day. Serum testosterone, estradiol and prolactin titres decreased in male and female rats with intact gonads given progesterone. While the levels of both luteinizing hormone (LH) and follicle stimulating hormone (FSH) decreased in male rats with intact gonads, only FSH decreased in female rats. The inhibitory effect of progesterone on serum estradiol, LH, FSH and prolactin persisted even after gonadectomy in male rats. This persistent inhibitory effect of progesterone was also seen on serum testosterone, FSH and prolactin levels of female rats. Ovariectomy modified progesterone action on LH, as is evident from the decreased levels of LH observed only in ovariectomized rats given progesterone. While progesterone had no effect on serum T3 and T4 in male rats, gonadectomy altered the levels of T3 and T4 in male and female rats. Progesterone increased the levels of T3 and decreased the levels of T4 in ovariectomized rats. Growth hormone (GH) and thyroid stimulating hormone (TSH) levels seem to be resistant to changes in progesterone titre, irrespective of the sex and gonadal status. The present data suggest the existence of a sex specific effect of progesterone on gonadotrophins. The data on T3, T4 and TSH reveals that progesterone has no effect on the pituitary thyroid axis in the presence of gonads.     

Demonstration of nuclear 3H-estradiol binding in hypothalamus and amygdala of female, androgenized-female, and male rats

The subcellular distribution of radioactivity in female, androgenized female, and male rats 1 hour after the iv administration of tritiated estradiol was examined. High regional specificity among nucle ar fractions of brain areas was seen with the preoptic-anterior hypothal amic area (POA-AH), median eminence-basal hypothalamus (ME-BH), and amygdala having much higher nuclear binding than other brain areas. Nuc lear binding was receptor-mediated in POA-AH, ME-BH, amygdala, dorsal hypothalamus, and the prehypothalamic area in all groups, as demonstrate d by competetive inhibition with diethylstilbestrol (DES). At this time period no differences between male and female rats in DES-blockable radioactivity levels of either nuclear or supernatant fractions in any brain area or pituitary were observed. Androgenized females had lower DES-blockable, nuclear radioactivity levels in POA-AH, ME-BH, and uteri but the % of total tissue radioactivity in the nuclei did not differ between groups for any tissue. These results demonstrate that males and females have similar estradiol uptake systems that are capable of high levels of nuclear binding in various brain areas.