Mitotic activity and its 24-hour rhythm in the ovarian follicles during the estrous cycle of a wild rat, Bandicota bengalensis

Mitotic activity in ovarian follicles was studied in relation to the size of the follicles during a 24-hour period (10.00, 16.00, 22.00 and 04.00 h) throughout the estrous cycle of the wild bandicoot rat (Bandicota bengalensis) to ascertain the cell proliferation rate and its 24-hour rhythm in the follicular tissue. In the bandicoot ovary, mitotic activity in the granulosa and thecal cells was highest in the follicles ranging from 201 to 400 micron in diameter. During the estrous cycle, mitotic activity of the granulosa cells was highest at estrus in follicles less than 601 micron, and at diestrus in follicles greater than 600 micron; while the mitotic trough was at proestrus in all the follicles. Thecal mitosis was significantly lower than mitosis of the granulosa cells. In most of the follicles, mitotic activity in the thecal cells was highest at diestrus and lowest at metestrus. In both the granulosa and thecal cells, the timing of mitotic peaks and troughs varied according to the size of the follicles and the stages of the estrous cycle. In the granulosa cells mitotic peaks were maximal in the daytime (10.00 h, 16.00 h) and in some cases at night (04.00 h); and mitotic troughs were primarily during the night (22.00 h, 04.00 h) and in some cases in the day (10.00 h). In the thecal cells, however, mitotic activity in most of the follicles was distinctly higher in the daytime (16.00 h) than at night (22.00 h, i.e., evening). Thus, a prominent 24-hour mitotic rhythm was noticed in the ovarian follicles of the bandicoot rat.     

A histochemical study of the binding of 125I-HCG to the rat ovary throughout the estrous cycle

Summary Changes in the distribution of the in vitro uptake of ¹²⁵I-HCG by the ovaries of adult rats were examined histochemically throughout the estrous cycle.Only in follicles wider than 500 m, occurring mainly at diestrus and proestrus, could granulosa cells bind the labelled hormone. The labelling increased with follicular size and decreased in intensity from the peripheral granulosa cells inwards. No uptake occurred in the oocytes, in the cells of the cumulus oophorus nor in the granulosa cells of the atretic follicles.The binding capacity of the newly-formed corpora lutea of estrus was less than that of preovulatory follicles. The uptake of ¹²⁵I-HCG by corpora lutea during the first cycle reached its maximum at diestrus but fell sharply by proestrus. The uptake was patchy in the corpora lutea of the second cycle and not significant in the older ones.The uptake of ¹²⁵I-HCG by thecae increased with follicular size and was greater in the thecae of atretic follicles than in the thecae of growing follicles of like size. There was a greater uptake in the last formed interstitial tissue than there was in older tissue.At proestrus, the uptake of ¹²⁵I-HCG was unaffected by the LH surge at 18.00h but had decreased slightly at 24.00 h.The implications of these data in relation to the regulation of receptor sites, is discussed.     

Compensatory ovulatory mechanisms operative after first ovulation in rats unilaterally ovariectomized prepubertally

Ovarian steroid contents and serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were measured during the days after first ovulation in rats unilaterally ovariectomized in late prepuberty. In addition, follicle counts were made at second estrus and second metestrus. During the cycle following first ovulation, ovarian estradiol contents in unilaterally ovariectomized (ULO) rats were significantly increased as compared to intact rats on the day of metestrus, on diestrus 1 and on second estrus. Ovarian progesterone was significantly increased on the days of metestrus, on diestrus 1, second proestrus and second estrus, but no differences were seen in ovarian androgen contents. After ULO there was an indication of an augmented FSH surge at the first and the second ovulation. Follicle counts revealed that the total number of healthy as well as of atretic antral follicles on the day of second estrus was significantly increased after ULO, due to increased numbers of the smallest antral follicles. At second metestrus the number of larger antral follicles (350-500 micron 3) and the total number of healthy antral follicles was higher after ULO. It is concluded that the compensatory process after ULO involved increased recruitment of small antral follicles. Activities in the remaining ovary were not simply doubled but a new hormonal balance was established.     

Follicular growth and kinetics during the estrous cycle, pregnancy and postpartum in the Indian mole rat (Bandicota bengalensis)

Follicular growth and kinetics were studied in detail in the ovaries of the Indian mole rat (Bandicota bengalensis) during various stages of the estrous cycle; days 7, 12, 15, 19, and 21 of pregnancy; and day 2 postpartum. The sizes of follicles, oocytes, nuclei, and nucleoli were measured. In all rats, regression coefficients, a, and intercepts, b, were calculated in oocyte/follicle, oocyte nucleus/follicle and oocyte nucleus/oocyte regressions. The oocyte reached its maximum size when the average follicle diameter was 117 microns in nonpregnant rats and 131 microns in pregnant rats. The oocyte nucleus attained maximum size when the follicle diameter was 110 microns during the estrous cycle and 111 microns during pregnancy and postpartum. Maximum values of the diameter of the largest antral follicle and average diameter of the four largest antral follicles were observed during proestrus (473 and 442 microns, respectively) and on day 21 of pregnancy (611 and 538 microns, respectively). Chi 2 analysis showed that distribution of various types of follicles was not independent of the stage of the estrous cycle and pregnancy. In estrus and metestrus most of the follicles were between stages I and V. However, by diestrus and proestrus, follicles of all size groups developed. The numbers of stage I and II follicles did not differ as pregnancy advanced. More stage V follicles were present on day 12 than on day 7 of pregnancy; however, their numbers decreased by day 15. Afterwards, progressive increase of stage V and (VI + VII) follicles was observed until day 21. This was accompanied by the shift of follicles from stage (III + IV) on days 19 and 21 of pregnancy and even of stage II on day 2 postpartum. Wherever possible, the results have been compared with previous observations in various rodent species.     

Prolactin receptors in the rat mammary gland. Change during the estrous cycle

Ovine prolactin (o-PRL) binding to mammary gland membranes was studied during the estrous cycle in the rat. Groups of rats were decapitated throughout the 4-day estrous cycle at 10 h00 on the days of diestrus I, diestrus II and estrus and at 10 h00, 12 h00, 16 h00 during the day of proestrus. Daily vaginal smears were taken to determine the stage of the estrous cycle which was also controlled by PRL and LH serum levels. Prolactin receptors were quantified in the 100 000 g pellet. For one Scatchard analysis, mammary gland membranes from 5 animals were pooled. Results given are the mean of 4 or 5 pools. Results obtained showed that the apparent affinity constant (KA) remained unchanged during the days of diestrus II and at all the times studied of proestrus and showed a slight but significant decrease on the days of estrus and diestrus I (or metestrus). The binding capacity did not vary from the day of diestrus II to the proestrus 16h00 (11.3 +/- 2.8 fmoles/mg protein) but sharply increased on the day of estrus (190.4 +/- 35.9 fmoles/mg protein). Binding capacity remained elevated on the day of diestrus I. This increase of PRL receptors on the day of estrous would appear to be an important step in preparing mammary gland for pregnancy and lactation.     

Effects of thymulin and GnRH on the release of gonadotropins by in vitro pituitary cells obtained from rats in each day of estrous cycle

The effects of thymulin and GnRH on FSH and LH release were studied in suspension cultures of anterior pituitary cells from female adult rats sacrificed on each day of the estrous cycle. The spontaneous release of gonadotropins by pituitaries, as well as their response to GnRH or thymulin addition, fluctuated during the estrous cycle. Adding thymulin to pituitary cells from rats in diestrus 1 increased the concentration of FSH; while in cells from rats in estrus, FSH level decreased. Thymulin had a stimulatory effect on the basal concentration of LH during most days of the estrous cycle. Adding GnRH increased FSH release in cells from rats in diestrus 1, diestrus 2, or proestrus, and resulted in higher LH levels in cells obtained from rats in all days of the estrous cycle. Compared to the GnRH treatment, the simultaneous addition of thymulin and GnRH to cells from rats in diestrus 1, diestrus 2, or proestrus resulted in lower FSH concentrations. Similar results were observed in the LH release by cells from rats in diestrus 1, while in cells from rats in proestrus or estrus, LH concentrations increased. A directly proportional relation between progesterone serum levels and the effects of thymulin on FSH release was observed. These data suggest that thymulin plays a dual role in the release of gonadotropins, and that its effects depend on the hormonal status of the donor's pituitary.     

Variations in concentration of oxytocin and vasopressin in the paraventricular nucleus of the hypothalamus during the estrous cycle in rats

Oxytocin (OT) and arginine-8-vasopressin (AVP) were measured by radioimmunoassay in micropunched hypothalamic neurosecretory nuclei of estrous cycling female Sprague-Dawley rats. In the paraventricular nucleus (PVN): the concentration (pg/microgram protein) of OT was significantly higher in rats in diestrus than during proestrus, estrus, or metestrus, while the concentration during metestrus was significantly greater than in proestrus and estrus; the concentration of AVP was significantly lower in animals in estrus than during the other three stages; because the paraventricular OT levels dropped before proestrus, the AVP/OT ratio was significantly greater in animals in proestrus than in diestrus, metestrus, and estrus. In the supraoptic nucleus (SON) a similar trend was noted: the concentration of OT was highest during diestrus, and AVP was lowest during estrus, though neither was significantly different from other stages. Because the OT and AVP cycles in the SON were asynchronous, the ratio of AVP to OT was significantly higher in proestrus than in metestrus or diestrus and significantly greater in estrus than during diestrus. In contrast to these two areas, peptide concentrations did not vary significantly across the estrous cycle in other sites of nonapeptide synthesis, i.e. the anterior commissural nucleus (ACN) and the suprachiasmatic nuclei (SCN).     

Quantitative and qualitative cytochemical analysis of changes in polysaccharides-proteins in rat ovulable and atretic ovarian follicles during the estrous cycle

Summary The glycosaminoglycan (periodic acid — Schiff, PAS) and hyaluronic acid (alcian blue) content of the membrana granulosa, zona pellucida and antrum of rat ovarian follicles was analyzed qualitatively and quantitatively during the estrous cycle in three types of follicles: ovulable, early atretic and late atretic. The qualitative analysis consisted of the conjunctive localization of PAS-reactive, fluorescent granules within the membrana granulosa. The quantitative analysis consisted of microdensitometric measurements of PAS and alcian blue staining within the zona pellucida and antrum of the ovulable and atretic follicles. For the localization of PAS granules within the granulosa cells, ovaries were removed on the day of proestrus, fixed in 6% paraformaldehyde, embedded in methacrylate and sectioned. Following the examination of the cells for fluorescence, the same section was stained with PAS and lead-hematoxylin. In ovulable follicles there was no fluorescence in the membrana granulosa while PAS granules occurred exclusively within the cells of the cumulus and corona radiata. In late atretic follicles, fluorescent-PAS reactive granules were located in the granulosa cells at the periphery of the follicle. During early atresia no fluorescence and very few PAS granules were observed in the granulosa cells. Since fluorescence is a marker for some lysosomes, these observations suggest that the PAS granules in the ovulable follicles may not be a type of lysosome. The amount of stain in the zona pellucida and antrum of the three follicular types was quantified using a scanning and integrating microdensitometer. On all days of the estrous cycle, PAS intensity was higher in the zona pellucida than in the antrum of the three follicular types. PAS staining in the respective antra was the same on all days of the estrous cycle. Intrafollicular PAS staining in the zonae pellucidae differed during the cycle. With respect to the zonae pellucidae, staining intensity in the three follicles was identical on estrus. On diestrus-1, staining intensity was the same in the ovulable and early atretic follicles and less in the late atretic follicle. By diestrus-2 and on proestrus, PAS intensity was highest in the zona pellucida of the ovulable follicle and less in the zona pellucida of both types of atretic follicle. In contrast to this pattern of staining, alcian blue staining intensity was identical in the zona pellucida of all follicles throughout the cycle. There was no difference in intra-antral alcian blue staining intensity on estrus and diestrus-2. On diestrus-1 and proestrus, staining intensity was greater in the antrum of the late atretic follicle than in the antra of the other follicular types. These studies indicate that glycosaminoglycan content is greater in the zona pellucida of the ovulable follicle of the rat on the last two days preceding ovulation than in the zona pellucida of either the early or late atretic follicles. In contrast, hyaluronic acid content remains constant in the zona pellucida of the three follicular types throughout the estrous cycle. These studies also give the first indication that, in the rat, the localization of PAS granules exclusively in the cumulus oophorus and corona radiata may be used to identify ovulable follicles.This work was supported by a research grant from the National Institute of Child Health and Human Development, HD-12684     

Quantitative determination of follicle size distribution in the guinea pig ovary after hemicastration and PMSG treatment

In order to investigate the action point of intraphysiological or supraphysiological elevation of FSH during the preovulatory period on follicular development, adult guinea pigs underwent unilateral ovariectomy on days 10, 12 and 14 of the estrous cycle (N = 6 each group). Thereafter, guinea pigs were injected twice daily with either vehicle or pregnant mare's serum gonadotropin (PMS). After 2 days, the remaining ovaries were removed. The resected ovaries were fixed, embedded in paraffin, serially sectioned (7 microns) and stained with Azan. All follicles greater than 70 microns were classified by size and atretic stage. The follicular size distribution was not affected by hemicastration at day 10, although the ratio of atretic follicles (greater than 400 microns) decreased from 51% to 32% (P less than 0.01). Hemicastration at day 12 increased the largest nonatretic population (70-99 microns group) from 17% to 26%, and the ratio of atretic follicles (greater than 400 microns) decreased from 35% to 23%. The peak size distribution of follicles was shifted from 70-99 microns to 200-299 microns by PMS, and follicles 600-899 microns in size contained an increased percentage of atresia, which resulted in the bimodal distribution of viable follicles greater than 400 microns. These data suggest that 2 day hemicastration promotes an influx of primordial follicles into growing follicles and suppresses the atretic process by a different mechanism depending on the date of hemicastration in the estrous cycle. Conversely, hemicastration + PMS accelerated viable follicle growth to increase the percentage of atresia.     

Expression of ghrelin in the porcine hypothalamo-pituitary-ovary axis during the estrous cycle

Ghrelin, a 28-amino acid acylated peptide produced mainly by the stomach, has various functions. Recent studies focus on its endocrine and/or paracrine effects in the regulation of the hypothalamo-pituitary-gonadal axis, that is, the role in reproduction. Previous data have shown that variation of ghrelin depended on the phases of estrous cycle in adult rat ovary. This study was to investigate the expression of ghrelin in the cyclic porcine hypothalamo-pituitary-ovary axis and stomach by semiquantitative RT-PCR and immunohistochemical method. Twenty virginal gilts were classified into four groups as the proestrus, estrus, diestrus1 and diestrus2. Results showed that expression of ghrelin mRNA in the hypothalamus changed with the estrous cycle, i.e., with the highest level in the proestrus and the lowest in the estrus. In the pituitary, the pattern of ghrelin mRNA expression during estrous cycle markedly decreased in the estrus and diestrus1. In the ovary, ghrelin mRNA exhibited with the highest level in the diestrus2 and the lowest in the proestrus, which was different from those in the hypothalamus and pituitary. In the stomach, the expression of ghrelin mRNA had the same tendency as that of the porcine ovary. In immunohistochemical experiment, ghrelin immunoreactive cells were predominantly located in the luteal compartment and growing follicles in the luteal phase of ovary. However, only few ghrelin immunoreactive cells were found in the proestrus ovary. In gastric mucosa, ghrelin immunoreactive cells were detected in the estrus, diestrus1 and diestrus2, but few ghrelin positive cells were seen in the proestrus. Results suggest that ghrelin may play a major role in the endocrine network that integrates energy balance and reproduction.     

Influence of the estrous cycle and prostaglandins on utero-ovarian vein blood flow in the rat.

The blood flow rate in the utero-ovarian vein (UOV) has been measured in adult female rats during the different phases of the estrous cycle. It was observed that the blood flow rate in the UOV is high at proestrus and at estrus and low during diestrus days 1 and 2. The intravenous injection of 10 mug PGF2alpha or PGE2 diminishes the blood flow rate in the UOV. The efficacy of the two PGs in reducing blood flow is different in the various phases of the estrous cycle, being maximal during the day of estrus.     

Age-related alterations in follicular development and hormonal profiles in rats with 4-day estrous cycles

Two experiments were conducted to examine the hypothesis that an alteration in follicular development is associated with advancing maternal age in the absence of prolonged estrous cycles. In Experiment 1, serum and four follicles (from one ovary per rat) were collected from young and middle-aged, 4-day cycling rats on estrus or metestrus. Number and diameter of nonatretic antral follicles greater than 200 microns in diameter were determined from serial sections of the other ovary from each rat. In Experiment 2, serum and follicles (12 +/- 2) from both ovaries were collected from young and middle-aged rats on each day of a 4-day estrous cycle. All microdissected follicles were assayed for estradiol-17 beta (E2) and all sera were assayed for E2, follicle-stimulating hormone, and luteinizing hormone by radioimmunoassay. Numbers of follicles greater than 400 microns in diameter did not differ, while numbers of follicles 200-400 microns in diameter were reduced in middle-aged rats compared to young rats (Experiment 1). The mean diameter of follicles greater than 400 microns in diameter and the follicular content of E2 was greater in middle-aged than in young rats. In Experiment 2, a greater proportion of large follicles were observed in middle-aged rats than in young rats on all days, and a greater proportion of follicles with high concentrations of E2 were observed on diestrus. We interpreted these data as indicative of an early age-related change in the control of follicular recruitment, growth, and maturation.     

Behavioral, follicular and gonadotropin changes during the estrous cycle in donkeys

Sexual behavior, follicular development and ovulation, and concentrations of circulating gonadotropins during the estrous cycle were studied during the summer in 7 jennies. Mean behavioral estrous length was 6.4 +/- 0.6 days (mean +/- SEM, n=19; 5.6 +/- 0.5 days preovulatory and 0.8 +/- 0.2 days post-ovulatory). Mean diestrous length was 19.3 +/- 0.6 days (n=14). Females in estrus typically showed posturing, mouth clapping, clitoral winking, urinating and tail raising. Mouth clapping began approximately one day sooner and lasted approximately one day longer than winking and tail raising, so that the total duration of clapping was significantly greater than for the other two signs. Follicular changes and concentrations of gonadotropins were determined for 14 estrous cycles (2 per jenny). The follicular end points [diameter of the largest follicle and number of large (>25 mm), medium (20-24 mm), and small follicles (<20 mm)] showed a significant day effect. The diameter of the largest follicle and the number of large follicles began to increase significantly 7 days prior to ovulation with a maximum value the day before ovulation. Medium follicles reached a maximum number 4 days prior to ovulation, and small follicles decreased significantly prior to ovulation. After ovulation, all follicular end points, except the number of small follicles, remained low for the next 12 days. Mean values of FSH were low during estrus and high during diestrus with 2 significant peaks, one 3 days and one 9 days after ovulation. In contrast, mean levels of LH were low during diestrus and high during estrus with a maximum value the day after ovulation. The LH profile showed a more prolonged gradual increase prior to ovulation, than that which has been reported for ponies and horses.     

Inhibition of estrus and corpora lutea function with Norgestomet

Forty-five nonpregnant, nonlactating, Angus and Brangus cows were utilized to determine how long a Norgestomet ear implant would inhibit estrus when administered at various stages of an estrous cycle. All cows completed a nontreated estrous cycle to ensure normal cyclicity. At the second observed estrus (estrus = Day 1), cows were randomly allotted to be treated at metestrus (Day 3 or Day 4, n = 15); at diestrus (Day 9 or Day 10, n = 14); or at proestrus (Day 15 or Day 16, n = 16). All cows received a 2-ml intramuscular injection of 3 mg of Norgestomet accompanied by a 6-mg Norgestomet ear implant, which remained in situ for 21 days, or until individual cows were observed in estrus. Estrus was inhibited for a mean (+/- SEM) of 18.7 +/- 0.7, 19.9 +/- 0.8, and 17.0 +/- 0.8 days, respectively, when cows were treated at metestrus, diestrus, and proestrus (metestrus and diestrus vs proestrus; P < 0.05). Estrus was inhibited for an entire 21-day implantation period in 27, 50, and 38% of cows treated at metestrus, diestrus, and proestrus, respectively (P > 0.10). Norgestomet inhibited estrus in all cows for 11, 17, and 11 days after implantation when treatment was initiated at metestrus, diestrus, and proestrus, respectively (P > 0.10). These data indicate that a 6-mg Norgestomet ear implant effectively inhibits estrus in all cows for a maximum of 11 days, with some cows exhibiting estrus by Day 12 with the Norgestomet implant in situ.     

Effect of methyl parathion formulation on estrous cycle and reproductive performance in albino rats

The animals were injected intraperitoneally with graded doses of methyl parathion at 1.5 to 3 mg/kg body weight for 15 days from the day of estrus. Results indicated that the methyl parathion treatment showed irregular estrous cycles, affect the duration of each estrous cycle, proestrus and diestrus were significantly changed in 2.5 and 3 mg treatment groups. But there was no significant change in the number and duration of each estrous cycle, duration of proestrus and diestrus in 1.5 and 2 mg methyl parathion treatment groups. However, there was a significant decrease in the duration of estrus, while there was no significant change in the duration of metestrus in all methyl parathion treatment rats when compared with those of the corresponding parameters of the control. There was no significant effect on number of live pups on day 1 and 5 except in 3 mg methyl parathion treatment group where it was significantly decreased. There was no significant change in reproductive indices like pregnancy, parturition, live birth and viability in all the methyl parathion treatment rats except the viability index in the highest dose.     

Ovarian prostaglandin endoperoxide synthase: cellular localization during the rat estrous cycle

The specific cellular localization of prostaglandin endoperoxide (PGH) synthase was studied throughout the rat estrous cycle. Animals were necropsied at 1300 h on each day of the 4-day cycle, and an additional group was necropsied at 2300 h on proestrus. Ovaries were removed and processed for cellular identification of PGH synthase by immunohistochemistry. At all stages of the cycle, intense immunostaining was observed in newly formed corpora lutea. Luteal cells were immunoreactive, but the connective tissue centrum was unstained. Interstitial tissue contained heavily labeled cells, whereas the germinal epithelium exhibited faint staining. During estrus, metestrus, and diestrus, thecal cells from preantral and antral follicles contained PGH synthase immunoreactivity, but granulosa cells were unstained. Faint staining of mural granulosa cells was observed first in 78% of preovulatory follicles (less than 400-microns diameter) in ovaries collected on the afternoon of proestrus. After the luteinizing hormone surge, 95% of the preovulatory follicles exhibited PGH synthase staining. The percentage of immunoreactive granulosa cells in these preovulatory follicles increased 4-fold in ovaries collected at 2300 h on proestrus. The presence of ovarian PGH synthase throughout the rat estrous cycle and the changes in cellular localization may reflect the potential role of PGs in follicular and luteal function.     

Cessation of transition-phase follicle growth in the guinea pig by follicle-regulatory protein

The granulosa cell produces a protein inhibitor of aromatase activity (follicle-regulatory protein: FRP), which recently was purified to homogeneity. To determine the possible involvement of FRP in follicular maturation, we examined the size distribution of follicles and their morphological patterns as well as serum steroid levels after the systemic administration of FRP and/or gonadotropin to guinea pigs, which have 5-6 days between luteolysis and ovulation in a 16-day cycle. FRP was partially purified from porcine follicular fluid by ammonium sulfate precipitation (0-35%), Dye Matrex Orange A Chromatography, dialysis, and lyophylization. To investigate the effect of pregnant mare's serum (PMS) during the periovulatory period in follicular development, adult guinea pigs underwent unilateral ovariectomy on Days 10, 12, and 14 of the estrous cycle (N = 6 each). Guinea pigs were injected twice daily with vehicle or PMS (5 IU) and 2 days thereafter the remaining ovaries were removed. Another group of guinea pigs received, in addition, intraperitoneal injections of FRP (1 mg) each morning from Day 8 of estrus until they were killed. The resected ovaries were fixed, embedded in paraffin, serially sectioned (7 micron), and stained with Azan for comparative study via light microscopy. All follicles greater than 400 micron were classified by size, and the atretic pattern was determined by mural granulosa cell pyknosis and antral sloughing. The distribution of follicular size was not affected by hemicastration at Day 10, although the percentage of total atretic follicles decreased. In the PMS-treated group, there was a significant decrease in the number of viable follicles (700-899 micron) after hemicastration. Also pronounced in follicles of this size was the lack of mid-atretic follicles. After injections of FRP for 3 or 5 days, the overall number of follicles was almost doubled as compared to the number found in the normal ovary. Additionally, there was a significant increase in the percentage of follicles that were recently atretic, although the total percentage of atretic follicles was unchanged. After hemicastration at Day 10 followed by FRP treatment for 2 days, the total percentage of atretic follicles in the remaining ovary decreased to 18% compared with 35% in the normal ovary, 46% in the hemicastrated plus PMS-treated group, and 38% in the hemicastrated and PMS- and FRP-treated group (all p less than 0.01). Treating the hemicastrated animal with PMS increased the percentage of atretic follicles in all groups.(ABSTRACT TRUNCATED AT 400 WORDS)     

Gonadotropin-releasing hormone binding sites in ovaries of normal cycling and persistent-estrus rats

The gonadotropin-releasing hormone (GnRH) binding capacity in ovaries and pituitaries of normal cycling rats at different stages of the estrous cycle and in ovaries of persistent-estrus rats was measured using radioligand-receptor assay (RRA). Persistent estrus was induced either by neonatal administration of testosterone propionate (1.25 mg s.c.) on the second day of life or by a hypothalamic suprachiasmatic frontal cut made with Halász' knife. All animals were killed during the critical period (1400-1600 h), and GnRH receptor was assayed. GnRH receptor levels in both ovaries and pituitaries changed during the estrous cycle. The total number of ovarian GnRH binding sites was significantly higher in proestrus than in diestrus 1, the stage in which the lowest level was found. When binding sites were expressed in fmol/mg ovary, the highest level was observed in diestrus 2; however, no changes were observed during the estrous cycle when GnRH binding sites were expressed as fmol/mg protein. Changes noted were very similar to those demonstrated in pituitary GnRH receptors in our present and previous experiments. Higher levels of pituitary binding sites were found in diestrus 2 and proestrus than in estrus and diestrus 1. The changes in the GnRH receptor levels were more striking in the pituitary than in the ovaries. It appears that the total number of ovarian GnRH binding sites was not altered in either of the two persistent-estrus groups, but that their concentration was significantly higher (expressed in fmol/mg ovary or fmol/mg protein) than on any day during the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of the estrous cycle and prostaglandins on utero-ovarian vein blood flow in the rat

The blood flow rate in the utero-ovarian vein (UOV) has been measured in adult female rats during the different phases of the estrous cycle. It was observed that the blood flow rate in the UOV is high at proestrus and at estrus and low during diestrus days 1 and 2. The intravenous injection of 10 μg PGF_2α or PGE₂ diminishes the blood flow rate in the UOV. The efficacy of the two PGs in reducing blood flow is different in the various phases of the estrous cycle, being maximal during the day of estrus.