Increased LH pulse frequency and estrogen secretion associated with termination of anestrus followed by enhancement of uterine estrogen receptor gene expression in the beagle bitch

The relationships among pulsatile LH secretion pattern, estrogen secretion, and expression of the uterine estrogen receptor gene were examined throughout the estrous cycle in beagle bitches. In Experiment 1, blood samples were collected from 30 bitches every 10 min for 8 h from a cephalic vein during different phases of the estrous cycle. An increase in the mean plasma levels of LH occurred from mid to late anestrus (P < 0.01). The LH pulse frequency increased (P < 0.01) from late anestrus to proestrus, and was strongly correlated (r = 0.96, P < 0.001) with the mean plasma level of estradiol-17 beta (E2). In Experiment 2, middle uterine samples, including the myometrium and endometrium, from 18 bitches were taken at 6 stages of the estrous cycle. The total number of estrogen receptors and nuclear estrogen receptor and its mRNA levels in the uterus also increased (P < 0.01) from late anestrus to proestrus. Mean plasma E2 level and the number of uterine estrogen receptor were positively correlated (r = 0.81, P < 0.05). In Experiment 3, nine bitches were ovariectomized in mid anestrus. Two weeks later they received a single injection of 10 or 50 micrograms/kg, i.m., estradiol benzoate. The number of uterine estrogen receptor and their mRNA levels for ovariectomized bitches were low, but increased (P < 0.05) after treatment with a low dose of estradiol benzoate. These results suggest that increases in LH pulse frequency and estrogen secretion are associated with termination of anestrus and that subsequent enhancement of uterine estrogen receptor expression may be up-regulated by estradiol.     

Estrous cycle-dependent histology and review of sex steroid receptor expression in dog reproductive tissues and mammary gland and associated hormone levels

This report describes normal histology of tissues from immature female dogs and sequential microscopic changes that occur during different stages of the estrous cycle in ovary, uterus, vagina and mammary glands. These observations are associated with a literature review of concurrent estrous cycle plasma hormone levels and expression of sex steroid receptors in these tissues. The combined review of different aspects of the estrous cycle in the dog provides readers with a comprehensive presentation and may guide investigators that are involved in testing compounds with hormonal effects in female dogs.     

Effects of endocannabinoid 1 and 2 (CB1; CB2) receptor agonists on luteal weight, circulating progesterone, luteal mRNA for luteinizing hormone (LH) receptors, and luteal unoccupied and occupied receptors for LH in vivo in ewes

Thirty to forty percent of ruminant pregnancies are lost during the first third of gestation due to inadequate progesterone secretion. During the estrous cycle, luteinizing hormone (LH) regulates progesterone secretion by small luteal cells (SLC). Loss of luteal progesterone secretion during the estrous cycle is increased via uterine secretion of prostaglandin F(2α) (PGF(2α)) starting on days 12-13 post-estrus in ewes with up to 4-6 pulses per day. Prostaglandin F(2α) is synthesized from arachidonic acid, which is released from phospholipids by phospholipase A2. Endocannabinoids are also derived from phospholipids and are associated with infertility. Endocannabinoid-induced infertility has been postulated to occur primarily via negative effects on implantation. Cannabinoid (CB) type 1 (CB1) or type 2 (CB2) receptor agonists and an inhibitor of the enzyme fatty acid amide hydrolase, which catabolizes endocannabinoids, decreased luteal progesterone, prostaglandin E (PGE), and prostaglandin F(2α) (PGF(2α)) secretion by the bovine corpus luteum in vitro by 30 percent. The objective of the experiment described herein was to determine whether CB1 or CB2 receptor agonists given in vivo affect circulating progesterone, luteal weights, luteal mRNA for LH receptors, and luteal occupied and unoccupied LH receptors during the estrous cycle of ewes. Treatments were: Vehicle, Methanandamide (CB1 agonist; METH), or 1-(4-chlorobenzoyl)-5-methoxy-1H-indole-3-acetic acid morpholineamide (CB2 agonist; IMMA). Ewes received randomized treatments on day 10 post-estrus. A single treatment (500 μg; N=5/treatment group) in a volume of 1 ml was given into the interstitial tissue of the ovarian vascular pedicle adjacent to the luteal-containing ovary. Jugular venous blood was collected at 0 h and every 6-48 h for the analysis of progesterone by radioimmunoassay (RIA). Corpora lutea were collected at 48 h, weighed, bisected, and frozen in liquid nitrogen until analysis of unoccupied and occupied LH receptors and mRNA for LH receptors. Profiles of jugular venous progesterone, luteal weights, luteal mRNA for LH receptors, and luteal occupied and unoccupied LH receptors were decreased (P≤0.05) by CB1 or CB2 receptor agonists when compared to Vehicle controls. Progesterone in 80 percent of CB1 or CB2 receptor agonist-treated ewes was decreased (P≤0.05) below 1 ng/ml by 48 h post-treatment. It is concluded that the stimulation of either CB1 or CB2 receptors in vivo affected negatively luteal progesterone secretion by decreasing luteal mRNA for LH receptors and also decreasing occupied and unoccupied receptors for LH on luteal membranes. The corpus luteum may be an important site for endocannabinoids to decrease fertility as well as negatively affect implantation, since progesterone is required for implantation.     

寒冷对雌性C57BL/6小鼠动情周期的影响*

目的:研究寒冷对雌性C57BL/6小鼠动情周期的影响。方法:12只雌性小鼠随机分为对照组、低温组,每组6只;低温组每天4℃暴露4 h,每天阴道涂片法观察小鼠动情状况,对照组饲养于常温动物房;每2 d称量体重,2周后心脏取血、子宫和卵巢,检测小鼠血清E2、FSH、LH、Prl、P水平,进行子宫、卵巢的组织病理学检查。结果:与对照组比较,低温组小鼠体重无显著性差异(P＞0.05),小鼠子宫脏器系数明显较低、动情间期明显延长(P＜0.01),血清FSH显著升高、Prl显著降低(P＜0.01),小鼠子宫腺管扩张,卵巢卵泡数量明显减少。结论:寒冷可使雌性C57BL/6小鼠动情周期延长,进而可能影响生殖功能。     

Involvement of gonadotropins in induction of luteolysis in pigs

In our previous study we have demonstrated that treatment of endometrial explants with LH increased 13,14-dihydro-15-ketoprostaglandin F(2alpha) (PGFM) accumulation in pigs. This was particularly visible on Days 14-16 of the estrous cycle. Action of gonadotropin in porcine endometrium appears to be mediated by LH/hCG receptors whose number is dependent on the day of the estrous cycle. In the current study i.v. infusion (1 hour) of hCG (200 IU) performed on Days 10 (n=4) and 12-14 (n=4) of the porcine estrous cycle did not affect plasma PGFM (ng/ml+/-SEM) concentrations. In contrast, administration of hCG on Days 15-17 produced, depending on plasma PGFM level before the infusion period, three different types of response: I. plasma PGFM surge of amplitude 0.62+/-0.15 was observed when the mean basal pre-infusion PGFM plasma level was 0.23+/-0.05 (n=6 gilts); II. the delayed PGFM surge of amplitude 0.62+/-0.15 was determined when basal pre-infusion PGFM level was 0.80+/-0.20 (n=6); and III. lack of PGFM response to hCG was found when basal pre-infusion PGFM level was 1.09+/-0.61 (n=6). Concentrations of plasma PGFM before and after saline infusion did not differ on Days 12-14 and 16 of the estrous cycle. In the next experiment blood samples were collected every 1 hour on Days 12-19 of the estrous cycle to determine concentrations of LH, PGFM and progesterone in four gilts. In particular gilts, plasma peaks of LH closely preceded surges of PGFM in 72.7, 84.6, 75.0 and 66.6 percent, respectively. The highest PGFM surges followed a decline in plasma progesterone concentration. We conclude that the increased PGF(2alpha) metabolite production after hCG infusion during the late luteal phase of the estrous cycle as well as the relationship between plasma LH and PGFM peaks suggest the LH involvement in the elevation of endometrial PGF(2alpha) secretion in pigs, and, in consequence, induction of luteolysis.     

The role of the adenylyl cyclase system in the regulation of corpus luteum function in the human and in nonhuman primates

We have reviewed the properties of luteinizing hormone/human chorionic gonadotropic (LH/hCG)-sensitive adenylyl cyclase (AC) of human corpus luteum (CL) and its regulation by several hormones and nonhormonal activators. We have also described the changes in enzyme activity in membrane preparations of human and cynomolgus monkey CL obtained at various stages of the menstrual cycle and pregnancy. The data have been analyzed with respect to the functional status of the luteal tissue and to the species differences among primate CL. In the menstrual cycle, luteal AC responsiveness to LH/hCG was detectable during the midluteal phase, but not during the late luteal phase or in the follicular phase of the following cycle. In addition, nonhormonal stimulation was high in CL obtained during the midluteal and late luteal phases, but declined drastically by the follicular phase of the next cycle. In early pregnancy, the enzyme was unresponsive to LH/hCG stimulation, yet its sensitivity to nonhormonal stimulation was similar, if not identical, to that of midluteal phase CL. Functional activity was also evident at the end of pregnancy. These results demonstrate that expression of AC activity in primate luteal membrane changes significantly with varying hormonal status under physiologic conditions. It is concluded that the AC system in luteal membranes is an effective model to study the mechanisms that regulate function and life span of the human and nonhuman primate CL.     

Identification of LH/hCG receptors in rabbit uterus

Luteinizing hormone (LH) is believed to act via specific receptors to control gonadal steroidogenesis and reproductive processes. Recently A. J. Ziecik, P. D. Stanchev, and J. E. Tilton (Endocrinology 119:1159, 1986) reported surprisingly that LH/hCG receptors were present in porcine uterus, a tissue not known to be a target for LH action. We report herein the identification of high-affinity LH receptors in the rabbit uterus. Uteri from adult New Zealand white rabbits were homogenized in Tris-HCl, 0.25 M sucrose. After filtration and sequential centrifugation, a partially purified pellet containing receptors was obtained. This preparation was incubated with a trace (1300 cpm) (50 pg) 125I-labeled chorionic gonadotropin and with various unlabeled protein hormones. Receptor bound was separated from free hormone by centrifugation at 1000 g. Affinity was estimated by Woolf plot analysis. Specific binding sites for LH/hCG were identified. The following Kd's were calculated: human LH, 1.6 X 10(-11); hCG, 0.5 X 10(-11); human TSH, 1.3 X 10(-9); and human FSH, 7.85 X 10(-9). The reaction of human FSH and TSH with the receptor is best explained by LH contamination of these hormones. A similar preparation of rat liver showed that no binding sites were present. Rabbit ovarian LH receptors had a Kd slightly higher at 4.1 X 10(-11) than that of the uterine LH receptors. Rabbit ovarian receptors were present at 2.27 X 10(-13) M/mg protein compared to uterine receptors at 4.65 X 10(-15) M/mg protein. We conclude specific- and high-affinity binding sites (receptors) for LH are present in the rabbit uterus. The function of these receptors remains unknown.     

Relationship between serum gonadotropins and pituitary immunoreactive gonadotropins and steroid receptors during the first FSH increase of the estrous cycle and following steroid treatment in heifers

The objectives were to determine the effects of (i) time during the first FSH increase of the estrous cycle (time-course study) and (ii) exogenous steroid treatment (steroid feedback study) on the relationship between circulating serum gonadotropins, and the proportions of pituitary cells immunoreactive for gonadotropins and steroid receptors during the estrous cycle in heifers. Pituitaries were collected from heifers (n=40) slaughtered at 13h (n=8), 30h (n=24) and 66h (n=8) after estrous onset, corresponding to before, during and after the first FSH increase of the estrous cycle. Heifers slaughtered during the FSH increase (at 30h) either received no treatment (n=8), or were treated (n=16) with estradiol benzoate and/or progesterone before slaughter. During the time-course study, the proportion of pituitary cells immunoreactive for FSH increased (P<0.05) during the first transient FSH increase reflecting serum concentrations. The proportion of pituitary cells immunoreactive for LH was unaltered, a reflection of serum LH concentrations. The proportion of estrogen receptors (ER)-alpha, but not ER-beta, was decreased (P<0.05) at 30h compared with at either 13 or 66h. During the steroid feedback study, exogenous progesterone with or without estradiol suppressed (P<0.05) the proportions of pituitary cells immunoreactive for gonadotropins, serum FSH concentrations and LH pulse frequency. Steroid treatment did not alter the proportion of pituitary cells positive for estrogen receptors (alpha and beta). While progesterone receptors (PR) were not detected in the anterior pituitary by immunohistochemistry during the early estrous cycle or in response to steroid treatment, quantitative real-time PCR revealed that mRNA for progesterone receptors was expressed at very low levels. The expression of pituitary PR mRNA was decreased (P<0.05) at 30 and 66h compared with 13h, and was suppressed (P<0.05) following steroid treatments. Alterations in pituitary steroid receptors are implicated in the differential regulation of gonadotropin secretion during the first transient FSH rise, but not in response to exogenous steroids. The time-course study and steroid feedback responses support the hypothesis that LH pulse frequency is tightly linked to regulation of GnRH pulse frequency. Serum FSH is regulated by its own synthesis, as reflected by pituitary FSH content and perhaps by alterations in pituitary sensitivity to circulating steroids by changes in steroid receptor content.     

Endocrine and local control of the primate corpus luteum

The primate corpus luteum is a transient endocrine gland that differentiates from the ovulatory follicle midway through the ovarian (menstrual) cycle. Its formation and limited lifespan is critical for fertility, as luteal-derived progesterone is the essential steroid hormone required for embryo implantation and maintenance of intra-uterine pregnancy until the placenta develops. It is well-established that LH and the LH-like hormone, CG, are the vital luteotropic hormones during the menstrual cycle and early pregnancy, respectively. Recent advances, particularly through genome analyses and cellular studies, increased our understanding of various local factors and cellular processes associated with the development, maintenance and repression of the corpus luteum. These include paracrine or autocrine factors associated with angiogenesis (e.g., VEGF), and that mediate LH/CG actions (e.g., progesterone), or counteract luteotropic effects (i.e., local luteolysis; e.g., PGF_2α). However, areas of mystery and controversy remain, particularly regarding the signals and events that initiate luteal regression in the non-fecund cycle. Novel approaches capable of gene “knockdown” or amplification”, in vivo as well as in vitro, should identify novel or underappreciated gene products that are regulated by or modulate LH/CG actions to control the functional lifespan of the primate corpus luteum. Further advances in our understanding of luteal physiology will help to improve or control fertility for purposes ranging from preservation of endangered primate species to designing novel ovary-based contraceptives and treating ovarian disorders in women.     

Pattern of ovarian progesterone secretion during the luteal phase of the ovine estrous cycle

Pulsatile secretion of progesterone has been observed during the late luteal phase of the menstrual cycle in the rhesus monkey and human. As the luteal phase progresses in each of these species, there is a pattern of decreased frequency and increased amplitude of progesterone pulses. The present study was designed to determine the pattern of progesterone secretion during the late luteal phase (Days 10-16) of the normal ovine estrous cycle. Five unanesthetized ewes, each bearing an indwelling cannula in the utero-ovarian vein, were bled every 15 min from 0800 h on Day 10 through 0800 h on Day 16 of the estrous cycle. With the computer program PULSAR, it was determined that progesterone secretion was episodic, with pulsations observed on all days. Analysis of variance was used to determine differences in frequency, amplitude, and interpeak interval (IPI) of progesterone pulses among ewes and days. The ewes averaged 8.0 +/- 0.63 pulses of progesterone per 24 h. Mean frequency of pulses was not different between days but showed differences between ewes. Mean amplitude of progesterone pulses was 7.0 +/- 0.27 ng/ml, with no differences observed either between days or between ewes. Mean IPI was 197 +/- 7.1 min, and, like frequency, the IPI was not different between days, but varied between ewes. No consistent temporal relationship was found between progesterone pulses and luteinizing hormone (LH), as determined by bioassay and radioimmunoassay, on Day 14 of the cycle in one ewe. The results indicate that progesterone secretion is episodic during the luteal phase of the ovine estrous cycle and is independent of LH pulses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Uterine blood supply as a main factor involved in the regulation of the estrous cycle--a new theory

The paper presents a new theory on the physiological mechanism of initiation of luteolysis, function of endometrial cells and protection of corpus luteum. This theory is based on previous studies published by the authors and their coworkers on the retrograde transfer of PGF2alpha in the uterine broad ligament vasculature during the estrous cycle, early pregnancy and pseudopregnancy. The studies were focused on cyclic changes in uterine blood supply and the apoptosis of endometrial cells. Moreover, the results of many other authors are cited. The statements of the theory are as follows: 1. The initiation of luteolysis is a consequence of regressive changes in the endometrium which are due to the reduction of the uterine blood supply below the level necessary to provide for the extended needs of active endometrium. 2. During the luteal phase, both a considerable increase in uterine weight and a decrease in blood flow through the uterine artery, resulting from increasing progesterone concentration, reduce the uterine blood supply. In comparison to the volume of blood flowing to the porcine uterus during the estrus period, only 30-40% of the blood volume is determined on day 12 of the estrous cycle. The uterine weight at that time is 40-60% larger than that in the early luteal phase. Thus, due to the considerable constriction of uterine blood vessels, there is a discrepancy between the requirement for oxygen and other factors transported by blood and the possibility of supplying the uterus with these substances. After reaching the threshold of uterine blood supply level, which in pigs takes place around day 12 of the estrous cycle, regressive changes and PGF2alpha release from endometrial cells occurs. 3. Estrogens and progesterone are the major factors affecting blood flow in vessels supplying the uterus. The factors that modulate, complement and support vasodilation and vasoconstriction are: PGE2, LH, oxytocin, cytokines, neurotransmitters and other local blood flow regulators. In some animal species these modulators, especially those of embryonic origin, may be crucial for the status of uterine vasculature. 4. During early pregnancy, the action of embryo signals (estrogens, cytokines), endometrial PGE2 as well as LH results in the relaxation of the uterine artery (pigs: day 12) and, consequently, in an increase in uterine blood supply. This reaction of the maternal recognition of pregnancy effectively prevents regressive changes in well developed endometrial cells to occur. 5. Local uptake and retrograde transfer of PGF2alpha into the uterine lumen during early pregnancy protects corpus luteum from PGF2alpha luteolytic action. 6. During the period of regressive changes resulting from the limited uterine blood supply, endometrial cells restrain PGF2alpha synthesis. They are, however, still capable of releasing prostaglandin when uterine blood supply is improved after the embryo appears in the uterus. This potential capability for PGF2alpha synthesis was demonstrated in in vitro studies when endometrial cells collected during its regressive phase were incubated in medium and stimulated by LH and oxytocin. 7. Prostaglandin F2alpha pulses in venous blood flowing from the uterus do not confirm pulsatile secretion of PGF2alpha. The pulses may result from the pulsatile excretion of PGF2alpha with venous blood according to the rhythmic uterine contractions associated with oxytocin secretion. 8. The results supporting this concept are presented and discussed in due course. The critique of Bazer and Thatcher's theory on exocrine versus endocrine secretion of prostaglandin F2alpha during the estrous cycle is also depicted.     

Changes in the levels of protein and steroid hormones in the plasma and steroid hormone receptors in the uterus of normal cycling guinea pigs

This study deals with the estrous cycle of guinea pigs in relation to sexual behavior, uterine weight, levels of gonadotropins, steroid hormones, and steroid hormone receptors in the uterus. The guinea pigs in this study showed cyclic changes in various reproductive functions broadly similar to other laboratory species studied. The increase in the uterine weight coincided with high concentration of steroid hormones (estradiol and progesterone) secreted during proestrus and estrus. The elevated levels of steroid hormone receptor concentrations in the uterus during these periods also confirm the role of these hormones. The rise in progesterone level from day 14 of the cycle was associated with lordosis and its related behavior. It was noted that the "estrus behavior" is the most accurate external marker for ovulation and sexual receptivity to males. It was also observed that there is an association between follicle-stimulating hormone and luteinizing hormone during the preovulatory period that was not demonstrated in previous studies.     

Control of Ovarian Function in Domestic Animals

Plasma hormone levels during the estrous cycle of the cow, ewe,and sow have been measured, and the patterns of secretion ofestrogens, progesterone, and luteinizing hormone during thecycle have been related to ovarian changes and other informationconcerning the cycle for each species. Peripheral plasma progesteroneand LH levels are generally inversely related during the cyclein each species, and it seems clear that progesterone exertsa negative feedback on LH secretion in all three species, atleast insofar as the cyclic release of preovulatory amountsof LH is concerned. Peak plasma progesterone levels are highestin the sow, lowest in the ewe, and intermediate in the cow.Plasma LH levels at estrus are highest in the ewe, lowest inthe sow, and intermediate in the cow. Sharp peaks in plasmaLH occur at the onset of estrus in the cow, and a few hoursafter the onset of estrus in the ewe and sow; these peaks areof about 6–8 hr duration. LH exerts a luteotrophic actionon the corpora lutea of all three species, and verylow levelsof LH secretion appear capable of maintaining the corpus luteumin the ewe and cow. There is no good evidence that prolactinis luteotrophic in any of these species. Three peaks of plasmaestrogen levels are seen in the ewe and the cow and these appearrelated to periods of accelerated follicle growth. One peakoccurs early in the cycle and before plasma progesterone levelsrise appreciably and another occurs during the luteal phasejust prior to corpus luteum regression. The third peak occursafter plasma progesterone levels decline and is associated withgrowth of the ovulating follicle. The luteal phase estrogenpeak has not been found in the sow. The rapid rise in bloodestrogens after the corpus luteum regresses facilitates thepreovulatorysurge of LH in all three species. Cyclical regressionof the corpus luteum in all three speciesappears to be underlocal control of the adjacent horn of the uterus. Exogenousestrogens are luteolytic in the cow and ewe, but luteotrophicin the sow. The ovaries of all three species contain very poorlydeveloped interstitial tissue probably because of the neailycomplete dedifftrentiation of the thecal cells during atresia.Thus, these animals lack an important source ofsteroid hormonespresent in the lodents and certain other species.     

Dynamics of Estrous Synchrony in Captive Gray Mouse Lemurs (Microcebus murinus)

Estrous synchrony in seasonal breeders can in principle be based on and shaped by environmental, internal, and/or social cues. We analyzed the dynamics of estrous synchrony for the first time in a seasonal, nocturnal primate species, the gray mouse lemur (Microcebus murinus). We compared successive estrous cycles and different levels of spatial proximity over two reproductive seasons in a captive population in order to identify possible social influences on estrous synchrony. The females exhibited a marked estrous synchrony at the beginning of each reproductive season, but we found no indication of a process of socially induced synchronization among them. Females housed in the same cage/room were not more strongly synchronized than females housed in different cages/rooms. Moreover, cycles desynchronized from the first to the second estrus of the season. Estrous cycle length did not depend on age, parity, or social housing conditions, but instead mainly on the individuality of the lemurs. This individuality, shown for the first time in a nocturnal primate species, is likely to be based on an endogenous rhythm with a genetic basis. We discuss possible social advantages, e.g., communal rearing, and disadvantages, e.g., mate choice and female-female competition, of estrous synchrony for nocturnal primates living in a dispersed individualized social network, and propose that a moderate flexibility within the individual cycle lengths probably enables the females to compromise between the different socioecological pressures.     

The rat uterine oestrogen receptor in relation to intra-uterine devices and the oestrous cycle [proceedings

There are changes in the nuclear content of the estrogen receptor in the rat uterus during the estrous cycle that are associated with changes in its physiology. The changes correlate with the concentrations of circulating estradiol. It appears that uterotrophic response to estradiol is a function of the nuclear receptor. The insertion of an IUD leads to changes in the treated uterine horn which appear to be the result of an increased responsitivity to circulating estradiol. The presence of an IUD did not alter the estrous cycle, gonadotropin, or corpus luteum function. The intracellular distribution of the estrogen receptor was investigated in normal uterine horns and in the horns with devices throughout the estrous cycle. Groups of 30 Wistar rats had a silk suture fitted in the lumen of 1 uterine horn. After 14 days the progress of these estrous cycles was determined. Rats were grouped according to the stage of the cycle on the 4th day. Rats were then killed and the uteri removed. Cytosol receptors were measured. The capacity of the cytosol estrogen receptor to bind to oligo(dT)-cellulose was determined. Cytosol protein, nuclear protein, and DNA were measured. At all stages of the estrous cycle, the wet weight and cytosol receptor of the treated horns were greater than the control horns. A slight increase in the capacity of cytosol receptor to bind to oligo(dT)-cellulose was noted at proestrus. The response elicited by the IUD was not considered to be due to an estrogenic response since the changes observed were not accompanied by a corresponding increase in the content of nuclear receptor.     

Serum luteinizing hormone and ovulatory response to luteinizing hormone-releasing hormone in the estrous and anestrous domestic cat.

A heterologous double antibody radioimmunoassay was developed to measure changes in serum luteinizing hormone (LH) concentrations in estrous and anestrous queens (female domestic cats), following a single injection of varying doses (0--25 microgram) of luteinizing hormone-releasing hormone (LH-RH). No increase in serum LH was detected in any of the estrous or anestrous queens following a single saline injection. Treatment with LH-RH resulted in a sharp increase in serum LH concentration in both estrous and anestrous queens. Ovulations as observed by the presence of corpora lutea at laparoscopy occurred in none of four, one of four, two of four and four of four estrous queens receiving 0, 5, 10 or 25 microgram of LH-RH, respectively. Mean serum LH concentration of the ovulating queens was maintained at a higher level and did not return to basal level at the same time as that of nonovulating queens. The data show that: LH-RH can cause release of LH in both estrous and anestrous queens and induce ovulation in the estrous cat; the magnitude of LH response is influenced by the stage of the reproductive cycle; and the duration during which LH is maintained above basal level may play a significant role in ovulation induction in this coitus-induced ovulatory species.     

Disruption of the tissue inhibitor of metalloproteinase-1 gene results in altered reproductive cyclicity and uterine morphology in reproductive-age female mice

Tissue inhibitor of metalloproteinase-1 (TIMP-1) is a multifunctional protein expressed in the uterus of essentially all species, yet the function of this protein is uncertain. To assess the role of TIMP-1 in the uterine events that occur during the murine estrous cycle, mature female TIMP-1 wild-type and null mice were monitored for reproductive cyclicity. Mice were sacrificed in each stage of the estrous cycle, and peripheral blood was collected and assayed for serum estradiol and progesterone content by RIA. Uterine morphology and TIMP-1, TIMP-2, TIMP-3, and TIMP-4 mRNA expression were also examined between genotypes in each stage of the estrous cycle. Disruption of the TIMP-1 gene product was associated with an altered reproductive cycle characterized by a significant decrease in the length of the estrus period in the null mice. Also during the period of estrus, null mice expressed significantly lower levels of uterine TIMP-3 mRNA expression, altered uterine morphology, significantly higher serum estradiol levels, and significantly lower serum progesterone levels compared to their wild-type counterparts. It is concluded from this study that TIMP-1 has a multifaceted role in regulating the murine reproductive cycle, and this control appears to be at the level of both the uterus and the ovary.     

Gonadal steroid modulation of brain opioid systems

It is becoming increasingly clear that the effects of the opioids and their synthetic analogs on anterior pituitary function largely depend on the steroid milieu present in the animal at time of drug administration. However, it is still unclear whether gonadal steroids regulate the opioid-modulated mechanisms by affecting the number of opiate receptors in the brain. To further investigate these issues, the effects of opiate agonists and antagonists on LH, FSH and prolactin (Prl) secretion have been studied in: (a) normal and castrated male rats, and (b) normally cycling female rats. The binding characteristics of the brain subclass of mu opiate receptors have been analyzed in the same group of experimental animals; this type of receptors seems to be particularly involved in the control of gonadotropin and Prl release. When injected intraventricularly into normal male rats, morphine (200 micrograms/rat) induced in a significant elevation of serum LH levels at 10 and 20 min. In long-term castrated animals the administration of the drug significantly reduced LH secretion at 40 and 60 min after the injection, the inhibition lasted up to 180 min. Morphine, when given intraventricularly to normal males, induced a conspicuous and significant elevation of serum Prl levels at 10, 20, 40 and 60 min after treatment. However, when the drug was administered to castrated rats, it did not significantly affect Prl release at any time interval considered. Morphine intraventricular injections did not modify serum FSH levels either in normal or in castrated male rats. The concentration of mu opiate receptors was found to be similar when measured in the whole brain of normal and orchidectomized rats. In adult cycling female rats, s.c. injections of naloxone (2.5 mg/kg) stimulated LH release in every phase of the estrous cycle; the magnitude of the responses was highly variable, being particularly elevated at 16.00 h of the day of proestrous and at 10.00, 12.00 and 14.00 h of the day of estrous. Conversely, LH response to naloxone was totally obliterated at 18.00 and 20.00 h of the day of proestrous, when the preovulatory LH surge was found to occur. The concentration of brain opiate receptors of the mu type showed significant variations during the different phases of the estrous cycle, with higher levels at 12.00 h of the day of proestrous and at 18.00 h of the day of estrous.(ABSTRACT TRUNCATED AT 400 WORDS)