Proestrous Stage Research Articles

New aspects of the neuroendocrine role of PACAP.

The presence of PACAP was revealed in the anterior pituitary with RIA, HPLC, and with the demonstration of its mRNA. The level of PACAP mRNA in the anterior pituitary is the highest during the proestrous LH surge. In our immunohistochemical studies we were able to demonstrate PACAP immunoreactive cells in the anterior pituitary. The shape and the distribution of PACAP immunoreactive cells were very similar to that of the gonadotropes; however, the number of PACAP cells was less than that of LH cells. Additionally, another PACAP-positive cell population with small diameter appeared in the proestrous stage, during pregnancy and lactation. Double labeling revealed that the major part of large PACAP cells exhibited LH immunoreactivity and those with a small diameter contained PRL. It is not clear whether the pituitary- or the hypothalamic-born PACAP, or both, influence pituitary LH and PRL secretion. I.c.v. administration of PACAP just prior to the critical period in the proestrous stage inhibited the expected ovulation and blocked the proestrus LH and PRL surge, although i.v. administration of PACAP had no effect. PACAP antiserum did not interfere with ovulation when i.c.v. or i.v. injection was used. Our results support the view that PACAP has a role in the control of LH and PRL secretion during the estrous cycle, pregnancy, and lactation. The inhibitory effect of PACAP on ovulation is mediated through the hypothalamus.

Acute treatment with 5-HT3 receptor antagonist, tropisetron, reduces immobility in intact female rats exposed to the forced swim test

The effects of tropisetron, a 5-HT3 receptor antagonist, were evaluated in adult Fischer female rats exposed to the Forced Swim Test (FST). Rats selected on the days of proestrus or estrus was immersed in a cylinder of water for 2 consecutive days. Rats were exposed to the FST for 15 min on day 1 (pretest), followed by a 5-min session (test), 24 h later. The proestrous–estrous group consisted of rats that were exposed to the FST on their proestrous stage (pretest); then 24 h later the same rats were exposed to the FST on their estrous stage (test). Rats in the estrous–diestrous group were exposed to the FST on their estrous stage (pretest) and 24 h later on their diestrous stage (test). Rats were injected intraperitoneally with saline or 1.0 or 2.0 mg/kg tropisetron 30 min prior to exposure to the cylinder on the test day. Immobility, swimming, and struggling behaviors were scored for 5 min. There was a significant decline in immobility after treatment with 2.0 mg/kg tropisetron in both groups. In addition, a significant decline in swimming was observed in the estrous rats (proestrous–estrous group) after treatment with 2.0 mg/kg tropisetron. There were no significant effects of tropisetron on struggling in any groups examined.

Simultaneous effect of lead and cadmium on granulosa cells: A cellular model for ovarian toxicity

Lead (Pb) and cadmium (Cd) are known reproductive toxicants, which accumulate in granulosa cells of the ovary. Female Charles foster rats were treated with sodium acetate (control), lead acetate and cadmium acetate either alone or in combination at a dose 0.05 mg/kg body weight intra-peritoneally for 15 days daily. Animals were killed at proestrous stage and granulosa cells were isolated from the ovaries. Binding of 125I-luteinizing hormone ( 125I-LH), 125I-follicle stimulating hormone ( 125I-FSH) and 17β-hydroxysteroid dehydrogenase activity were measured. As these receptors are localized on the surface of the cell membrane, we also estimated the membrane parameters of these cells. Our results demonstrated that both lead and cadmium caused a significant reduction in gonadotropin binding, which altered steroidogenic enzyme activity of granulosa cells. These changes exhibited a positive correlation with membrane changes of the granulosa cells.

Estrous Cycle Specific Immunolocalization of Different Domains of the Epidermal Growth Factor Receptor in the Porcine Oviduct

Although porcine uterus is known to contain active and inactive forms of epidermal growth factor receptor (EGF-R), the latter consist of the extracellular domain only; it is currently unknown whether different EGF-R isoforms are expressed in the porcine oviduct during estrous cycle. Therefore, we used two different monoclonal antibodies, one against the extracellular and the other against the cytoplasmic domain of the EGF-R, to investigate cycle-dependent and cell-type-specific expression of full-size and truncated receptor forms. At metestrus, the majority of epithelial cells of the oviduct were strongly immunopositive for both antibodies, indicating the presence of the full-size receptor. In diestrous and proestrous stages, we found a low level of cytoplasmic but no extracellular EGF-R staining in epithelial cells. While the staining intensity of cytoplasmic domain of the EGF-R was only faint or absent in muscular tissue and blood vessels throughout the estrous cycle, extracellular domain of the EGF-R exhibited a strong immunostaining of smooth muscle cells and vascular smooth muscle cells, especially in diestrous and proestrous stages. There was no significant difference between the oviductal ampulla and isthmus in either the intensity or the pattern of both cytoplasmic and extracellular EGF-R immunostaining. We conclude that the restricted presence of the functional full-size receptor to the epithelial layer indicates a specific role during early embryonic development, whereas truncated EGF-R forms may potentially regulate contractions and blood flow in the oviduct.

Sex hormone regulation of anti-bacterial activity in rat uterine secretions and apical release of anti-bacterial factor(s) by uterine epithelial cells in culture

In mature female rats, sex hormones regulate the reproductive (estrous) cycle to optimize mating and fertility. During the part of the estrous cycle when mating occurs, and when estrogen is the dominant sex hormone, the uterus is susceptible to infection with bacteria that can be deleterious for survival and fertility. The present study investigated whether sex hormones regulate innate immunity in the female reproductive tract by affecting the secretion of an anti-bacterial factor(s) in the rat uterus. Uterine fluids from intact rats at the proestrous stage of the estrous cycle significantly inhibited Staphylococcus aureus growth. When ovariectomized rats were treated with estradiol, anti-bacterial activity against both S. aureus and Escherichia coli increased in uterine secretions with hormone treatment. In contrast, rats injected with either progesterone and estradiol or progesterone alone displayed no bactericidal activity indicating that progesterone reversed the stimulatory effect of estradiol on anti-bacterial activity. In other studies, isolated uterine epithelial cells from intact animals were grown to confluence and high transepithelial resistance on cell inserts. Analysis of apical secretions indicated that a soluble factor(s) is released by polarized epithelial cells which inhibits bacterial growth. These results demonstrate that sex hormones influence the presence of a broad-spectrum bactericidal factor(s) in luminal secretions of the rat uterus. Further these studies suggest that epithelial cells which line the uterine lumen are a primary source of anti-bacterial activity.

Stereological characterization of bovine ( Bos taurus) cumulus-oocyte complexes aspirated from small antral follicles during the metestrous and proestrous phases

Bovine cumulus-oocyte complexes (COCs) aspirated from slaughterhouse ovaries are used for in vitro maturation and fertilization after selection on the basis of morphological appearance of the cumulus and ooplasm. In this context, a quantitative characterization of COCs could provide additional criteria for selecting the most competent complexes. Bovine COCs from small (1–4 mm) antral follicles were aspirated from metestrous and proestrous stage ovaries of Holstein–Friesian cows, fixed in glutaraldehyde, randomly embedded in glycol-methacrylate, and sectioned at 20 μm. The unbiased nucleator principle of stereology was used for estimating the mean volumes of complexes, oocytes, cumulus cells, and nuclei of oocytes and cumulus cells. The thickness of the zona pellucida and the relative numerical percentages of the several morphological types (C1, C2 and C3) of cumulus cells were also evaluated. The optical dissector procedure was used for cumulus cell sampling. Quantitative data show that the variability among complexes is generally high, especially for the volume of COCs. There were no linear correlations between the studied parameters, except between the volume of the oocyte and nucleus at metestrus. At proestrus, the volumes of COCs, oocytes and nuclei of oocytes, the volume of follicular cells and the thickness of the inner zona pellucida, were significantly higher than at metestrus. The relative numerical frequency of follicular type C1 cells was lower whereas that of type C3 cells was higher at proestrus than at metestrus. In conclusion, small antral follicles had larger COCs and oocytes at proestrus compared to metestrus and the COCs also had a higher percentage of follicular type C3 cells. Results suggest that for the same type of follicle size there may exist different functional populations of COCs at distinct stages of the bovine ovarian cycle.

The role of PACAP in gonadotropic hormone secretion at hypothalamic and pituitary levels.

The presence of pituitary adenylate cyclase-activating polypeptide (PACAP) and its mRNAin the three levels of the hypothalamo-hypophyseal-ovarian axis was previously demonstrated using immunohistochemistry, in situ hybridization, and reverse transcriptase polymerase chain reaction (RT-PCR). In the hypothalamus, PACAP is present in neuroendocrine effector cells and in the median eminence. In the anterior pituitary and ovary, PACAP is transiently present during the proestrous stage of the estrous cycle. In the pituitary, PACAP was observed in gonadotropes. In the ovary, PACAP was demonstrated in the granulosa cells of the preovulatory ovarian follicles. The effect of PACAP on luteinizing hormone (LH) secretion was demonstrated in in vivo and in vitro models. In our work we have studied the role of PACAP in gonadotropic hormone secretion at hypothalamic and pituitary levels. At the hypothalamic level, PACAP, administered intracerebroventricularly to female rats before the critical period of the proestrus stage, can inhibit LH release and ovulation. Its inhibiting effect is mediated through corticotropin-releasing factor (CRF) and endogenous opioids. PACAP administered to neonatal female rats delayed the onset of puberty by influencing the luteinizing hormone-releasing hormone (LHRH) neuronal system. In the pituitary gland, the release of PACAP depended on the stage of the estrous cycle and on the time of day the animals were sacrificed. On the day of proestrus, the number of PACAP-releasing cells showed a diurnal change with two peaks (in the morning and in the evening). The peak was much higher in the evening at the end of the LH surge than in the morning.

PACAP38 and PACAP27 administered intracerebroventricularly have an opposite effect on LH secretion

The effect of PACAP38 on the LH surge and ovulation was compared with that of PACAP27 and VIP in the same model. The peptides were administered intracerebroventricularly before the critical period of the proestrous stage. PACAP38 was able to inhibit ovulation and to prevent the preovulatory LH surge; however, PACAP27 did not inhibit the ovulation and VIP inhibited the ovulation in 2/11 animals. In those animals of the last two groups in which ovulation occurred, the preovulatory LH surge was higher than in control rats. It is speculated that the opposite effect of PACAP38 and PACAP27 on the preovulatory LH surge and ovulation is possibly mediated through different receptors.

Fertility maintenance and 5-fluorouracil timing within the mammalian fertility cycle

The mammalian fertility cycle is responsible for tight coordination of molecular, biochemical and cellular events. We have investigated whether timing of 5-fluorouracil (5-FU) chemotherapy within this cycle affects its reproductive toxicology. When this very short half-life, largely S-phase active cytotoxic antimetabolite is administered during the estrous phase (immediate postovulatory) of the fertility cycle, female mice suffer greater subsequent loss of fertility (decreased successful pregnancy rate) than those mice receiving 5-FU during the metestrous, diestrous, or proestrous stages. Pups subsequently born to mothers given 5-FU during the estrous and metestrous stages are of lower weight compared with those born to mothers treated with 5-FU during diestrus or proestrus. Acute lethality is similarly affected by the fertility cycle timing of 5-FU administration. Treatment during estrus is associated with the greatest overall lethal toxicity. This finding indicates that the 5-FU susceptibility of nonreproductive tissues, the integrity of which is essential for survival, may also be coordinated by the mammalian fertility cycle. It is concluded that optimizing the fertility cycle timing of 5-FU (e.g., during the periovulatory, proestrous stage) diminishes the frequency and severity of long-term reproductive damage.

Role of PACAP in the Regulation of Gonadotroph Hormone Secretion during Ontogenesis: A Single Neonatal Injection of PACAP Delays Puberty and Its Intracerebroventricular Administration before the Critical Period of Proestrous Stage Blocks Ovulation in Adulthooda

Annals of the New York Academy of SciencesVolume 865, Issue 1 p. 590-594 Role of PACAP in the Regulation of Gonadotroph Hormone Secretion during Ontogenesis: A Single Neonatal Injection of PACAP Delays Puberty and Its Intracerebroventricular Administration before the Critical Period of Proestrous Stage Blocks Ovulation in Adulthooda K. KÖVES, Corresponding Author K. KÖVES Corresponding author: Katalin Köves, M.D., Ph.D., Department of Human Morphology, Semmelweis University Medical School, Tüzoltó u. 58; Budapest, H-1094 Hungary; Tel.: (36)1 - 215 6920; Fax.: (36)1 - 215 3064; E-mail: [email protected]Search for more papers by this authorJ. MOLNÁR, J. MOLNÁR Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorO. KÁNTOR, O. KÁNTOR Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorA. LAKATOS, A. LAKATOS Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorK. FÓGEL, K. FÓGEL Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorM. KAUSZ, M. KAUSZ Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorM. C. VANDERMEERS-PIRET, M. C. VANDERMEERS-PIRET Department of Medicine and Pharmacology, Laboratory of Chemical; Biology and Nutrition, Liberty University of Bruxelles, BelgiumSearch for more papers by this authorA. SOMOGYVÁRI-VIGH, A. SOMOGYVÁRI-VIGH Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorA. ARIMURA, A. ARIMURA US-Japan Biomedical Research Laboratories, Tulane University Hebert; Center, Belle Chasse, Louisiana 70037 USA Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this author K. KÖVES, Corresponding Author K. KÖVES Corresponding author: Katalin Köves, M.D., Ph.D., Department of Human Morphology, Semmelweis University Medical School, Tüzoltó u. 58; Budapest, H-1094 Hungary; Tel.: (36)1 - 215 6920; Fax.: (36)1 - 215 3064; E-mail: [email protected]Search for more papers by this authorJ. MOLNÁR, J. MOLNÁR Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorO. KÁNTOR, O. KÁNTOR Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorA. LAKATOS, A. LAKATOS Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorK. FÓGEL, K. FÓGEL Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorM. KAUSZ, M. KAUSZ Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorM. C. VANDERMEERS-PIRET, M. C. VANDERMEERS-PIRET Department of Medicine and Pharmacology, Laboratory of Chemical; Biology and Nutrition, Liberty University of Bruxelles, BelgiumSearch for more papers by this authorA. SOMOGYVÁRI-VIGH, A. SOMOGYVÁRI-VIGH Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this authorA. ARIMURA, A. ARIMURA US-Japan Biomedical Research Laboratories, Tulane University Hebert; Center, Belle Chasse, Louisiana 70037 USA Department of Human Morphology and Developmental Biology, Semmelweis University Medical School, Budapest, Hungary H-1094Search for more papers by this author First published: 07 February 2006 https://doi.org/10.1111/j.1749-6632.1998.tb11242.xCitations: 9 a This work was partially supported by OTKA grant T020403 (k.k. and M.k.), and National Institutes of Health Grant DK-09094 (A.A.). Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume865, Issue1VIP, PACAP, AND RELATED PEPTIDES: THIRD INTERNATIONAL SYMPOSIUMDecember 1998Pages 590-594 RelatedInformation

Localization of connective tissue growth factor during the period of embryo implantation in the mouse.

A role for connective tissue growth factor (CTGF) in reproductive function has been suggested from recent studies in the pig. To extend these findings, we have analyzed the immunohistochemical localization of CTGF during the estrous cycle and early pregnancy in mice. During the diestrous and early proestrous stages, CTGF was localized at high levels to both luminal and glandular uterine epithelial cells and at much lower levels in the stroma or myometrium. Epithelial expression of CTGF was considerably reduced at estrus. On Days 1.5-3.5 of pregnancy, CTGF was localized mainly to the uterine epithelial cells, which showed a substantially reduced level of CTGF on Day 4.5. On Days 5.5 and 6.5, CTGF was present at high levels in uterine decidual cells. CTGF was detected in the trophectoderm and inner cell mass of the preimplantation embryo on Day 4.5 and became preferentially localized to embryonic endoderm and mesoderm on Days 5.5-6.5. Multiple mass forms of CTGF (Mr 14 000-38 000) were present in endometrial extracts and uterine luminal flushings. Collectively, these data support a role for CTGF in uterine cell growth, migration, adhesion, and extracellular matrix production during the estrous cycle and early pregnancy, as well as in early development of the embryo.

Estrogenic effects on urinary 6-sulphatoxymelatonin excretion in the female rat.

The pattern of melatonin production during the estrous cycle of the rat was measured by monitoring urinary 6-sulphatoxymelatonin (aMT.6S) excretion. Adult rats were maintained under a 14L:10D photoperiod and urine was collected at hourly intervals over a 5-day period using an automated collection system; the concentration of aMT.6S was assayed by RIA and hourly outputs were calculated. Each nightly collection of urine was assigned to an estrous cycle stage as determined by the vaginal smear of the preceding morning. Total aMT.6S excretions (mean +/- SEM) during estrous, metestrous, diestrous, and proestrous stages were 493 +/- 49, 539 +/- 44, 562 +/- 40, and 646 +/- 51 pmol/night, respectively (n = 7). The excretion of aMT.6S was significantly higher on the night of proestrus compared to each of the other stages (P < 0.05). To determine whether estrogen was responsible for the increased aMT.6S excretion during proestrus, rats were studied before and after ovariectomy and following implantation with estradiol implants. Total overnight aMT.6S excretion was reduced by 31% in ovariectomized animals relative to the intact state (P < 0.05) and restored to the intact levels by administration of estradiol (P < 0.05). It was concluded that estradiol can modulate melatonin production in adult rats, and that the changing pattern of aMT.6S excretion throughout the estrous cycle may provide a basis for a functional relationship between pineal activity and reproduction in this species.

PACAP blocks the ovulation in rat administered icv before the critical period of proestrous stage

PACAP blocks the ovulation in rat administered icv before the critical period of proestrous stage

Occurrence of Deoxyribonucleic Acid Fragmentation during Prolactin-Induced Structural Luteolysis in Cycling Rats1

We determined whether fragmentation of genomic DNA, one of the hallmarks of apoptosis, occurs during structural luteolysis in cycling rats. Corpora lutea (CL) were collected from rats at each estrous cycle stage (1800 h), and fragmented DNA was extracted. Only CL from rats at the proestrous stage showed distinct DNA fragmentation. To determine the period of occurrence of DNA fragmentation, CL were collected at several points between 1200 h on the day of proestrus and 0600 h on the day of estrus. Distinct DNA fragmentation was observed from 1800 h (proestrus) to 2400 h (proestrus), and the extent was significantly lower at 0600 h (estrus). It is known that prolactin (PRL) induces structural luteolysis in rats. To examine the role of PRL in luteal DNA fragmentation, 2-bromo-alpha-ergocryptine (BE) was used to suppress the PRL surge on the day of proestrus. CL collected at 1800 h from BE-treated rats did not show distinct DNA fragmentation, and PRL injection offset the effect of BE. Histochemical analysis with a 3'-end labeling technique confirmed the occurrence of DNA fragmentation in luteal tissue. These results suggest that apoptotic cell death occurs during PRL-induced structural luteolysis.

Vascular smooth muscle reactivity to norepinephrine in ovariectomized rats: Relationship to vascular PGE 2/PGF 2α ratio

1. 1. We have recently demonstrated that, in normal female rats, vascular reactivity (VR) and vascular prostaglandin-E 2 (PGE 2) and prostacyclin production are influenced by the ovarian cycle. 2. 2. In this study, we investigated the vascular reactivity (VR) of isolated rat thoracic aorta to norepinephrine (NE 10 −12-10 −6M) in ovariectomized rats (OVX-rats), 48 hr and 8 days after surgical removal of the ovaries and in normally cycling rats (NR) at the proestrus stage of the estrous cycle, when the level of circulating estrogen was higher. 3. 3. In addition, we determined the vascular synthesis of PGE 2 and protaglandin-F 2α (PGF 2α) in both groups of OVX-rats, and in NR during the proestrous stage. 4. 4. The results showed that VR to NE 10 −12-10 −10 M was similar between OVX-rats and normal rats. 5. 5. However, aortic rings obtained from both groups of OVX-rats showed a significant increase of the contraction response induced by NE 10 −9-10 −6 M. 6. 6. Furthermore, the contractile response to NE 10 −7-10 −6 M was greater in the aortic rings from OVX-rats 8 days after ovariectomy compared to OVX-rats 48 hr ( p < 0.001). 7. 7. Vascular PGE 2 and PGF 2α synthesis (ng/mg protein/hr) was significantly higher in both groups of OVX-rats than NR. But the vascular PGF 2α synthesis increased more than PGE 2 in these OVX-rats, thus the ratio PGE 2/PGF 2α was decreased significantly in both groups of OVX-rats ( p < 0.01 and p < 0.001 OVX-rats 48 hr and 8 days after surgery, respectively) compared to NR-ratio.

Hormonal influences of detoxication in the rat ovary on enzymes in comparison with the liver

Variations in the total capacity of the rat ovary to metabolize xenobiotics during different phases of the estrous cycle were studied. The level of the conjugating enzymes, phenol UDP-glucuronosyltransferase (pUDPGT; EC 2.4.1.17), phenol sulfotransferase (pST; EC 2.8.2.1) and glutathione transferases (EC 2.5.1.18) was determined in the ovary and compared with the corresponding hepatic activities. In addition, catalase (EC 1.11.1.6) and NAD(P)H: quinone oxidoreductase (EC 1.6.99.2) two other detoxifying enzymes, were assayed. In order to study the hormonal influences on detoxifying enzymes, mature rats were characterized with respect to their stage in the estrous cycle. Immature rats were treated with pregnant mare's serum gonadotropin (PMSG) for 2 or 3 days to enrich the ovaries in preovulatory follicles or corpora lutea, respectively. The present study demonstrates that ovarian pUDPGT and pST activities are increased 936% and 175%, respectively, in ovaries enriched in corpora lutea compared to ovaries from untreated immature rats. Increases in these activities in mature rats during the metestrous stage of the estrous cycle compared to the proestrous stage were also noted. In the liver pUDPGT activity is increased significantly (1.6-fold) in immature rats with ovaries enriched in preovulatory follicles compared to untreated rats. Both ovarian pST and pUDPGT activities increased in mature rats treated with PMSG (“hyperstimulated”), while in the liver only pST was increased by such treatment. Ovarian glutathione transferase activity proved not to be dependent on the hormonal fluctuations associated with the estrous cycle. However, in the liver of mature rats treated with PMSG, this activity increased 2-fold compared to the untreated immature rats. The catalase activity found in the ovarian mitochondrial fraction was approx. 10-fold higher than in the cytosolic fraction, independent of the hormonal status. Moreover, we found a significant 1.4-fold increase in peroxisomal catalase activity in the mitochondrial fraction of immature rats treated with PMSG, both when enriched in preovulatory follicles and in corpora lutea. In the liver cytosolic catalase activity decreased several-fold in immature rats following PMSG treatment. We did not find any variations in ovarian NAD(P)H: quinone oxidoreductase activity during the estrous cycle, whereas in the liver this activity decreased in the luteal phase, as it did in mature rats treated with PMSG. From this study and earlier investigations in our laboratory, we conclude that cyclic variations due to hormones of the estrous cycle of the major 7,12-dimethylbenz(a)anthracene (DMBA)-metabolizing phase I enzymes in the ovary are not accompanied by increases in the activities of the corresponding phase II enzymes. An increased steady-state level of reactive intermediates around the time of ovulation may thus increase the risk of cellular damage, e.g. in the oocyte, during this period.

Circadian and estrous cycle-dependent variations in blood pressure and heart rate in female rats

To determine whether cardiovascular functions are controlled by the endogenous circadian system and whether they change with the estrous cycle in female rats, we measured mean arterial pressure (MAP), heart rate (HR), and spontaneous activity (ACT) of female rats using an implantable radiotelemetry device and a computerized data-collecting system. Under a 12:12-h light-dark (LD) cycle, these parameters exhibited daily rhythms that were entrained to the photic cycle. The patterns of the daily rhythms varied with estrous cycles, and variations were particularly marked in the proestrous stage. During the dark period of this stage, ACT levels were significantly higher, but HR was significantly lower than in other stages. Although the peak MAP occurred within 2 h after the onset of the dark phase in three of the estrous stages, it occurred around midnight in the proestrous stage. Such estrous cycle-dependent variations were eliminated by ovariectomy. The implantation of 17 beta-estradiol produced a gradual increase in MAP and an abrupt decrease in HR. During constant darkness, all three parameters were free running, maintaining the same internal phase relationships with each other as during LD cycles. These results indicate that daily variations in these parameters were controlled by the endogenous circadian oscillating system, that they vary with the estrous cycle in female rats, and that estrogen may be responsible for these estrous cycle-dependent variations.

Brain Lys-aminopeptidase activity. Changes during cycle and pregnancy.

Lys-aminopeptidase activity levels during the estrous cycle (estrous and proestrous, in the morning and afternoon) and the pregnancy (2nd, 7th, 14th and 20th day postinsemination and the parturition day), in several areas of the rat brain, were studied in this research. The selected brain regions were the frontal, parietal and occipital cortices, olphactory bulbus, thalamus, hypothalamus, hippocampus, amygdala, striatum and pituitary gland. The most significant changes were shown in the hypothalamus and the pituitary gland. Thus, in these areas, the higher cyclic enzyme levels were found in the proestrous stage. During pregnancy, there was a rise on the 7th and 14th days, with a decrease on the 20th day. Also, similar changes in the occipital cortex, striatum, hippocampus and amygdala were appreciated, but fewer than those observed in the hypothalamus and the pituitary. In conclusion, the activity of the aminopeptidase under study fluctuates during the estrous cycle and during pregnancy, as well as in the hypothalamic-pituitary axis and also in several extrahypothalamic areas of the rat brain.

Brain soluble and membrane-bound Tyr-aminopeptidase activities during the stages of estrous and proestrous in the female rat

Brain Tyr-aminopeptidase activity levels during two stages of the rat estrous cycle (estrous and proestrous), are described in this research. The study includes the activities of the soluble and the membrane-bound forms. Soluble Tyr-aminopeptidase activity shows a significant increase during the proestrous stage in the hypothalamus. The complete membrane-bound activity did not significantly change at any point. However, a significant rise was found in the membrane-bound puromycin insensitive aminopeptidase activity in the hypothalamus and the pituitary gland during the proestrous phase.

Progesterone does not mediate the inhibition of pineal melatonin production during the rat proestrous night

N-Acetyltransferase (NAT) activity and melatonin content were determined in pineal glands obtained during the proestrous stage of the rat estrous cycle. In control animals, both pineal NAT activity and melatonin levels were reduced during the first hours of proestrous night, as compared with day-time proestrous levels. The administration of antiprogestagen RU486, in a dose which blocked the preovulatory rise of serum luteinizing hormone and follicle-stimulating hormone levels, failed to prevent the reduction of pineal melatonin synthesis associated with the ovulatory events at proestrous night. These results suggest that estradiol, but not progesterone, might be the ovarian hormone responsible for the inhibition of pineal melatonin synthesis observed in the normal cycling female rat during proestrous night.