Corpus Luteum Of Estrous Cycle Research Articles

Inhibin .ALPHA.-Subunit mRNA Is Expressed in the Corpus Luteum of the Pregnant Mare.

The expression of inhibin α-subunit mRNA was examined in the corpus luteum (CL) of pregnant mares. Corpora lutea were obtained from pregnant mares at 50 h, 94 h after ovulation and on 30, 60, and 90 days of pregnancy. Northern blot analysis, using a cDNA specific to equine inhibin α-subunit as a probe revealed that the expression level of its transcript continued to decline until 30 days after ovulation. However, on day 60 of pregnancy, the level increased similar to that at 94 h after ovulation. On day 90 of pregnancy, the level declined again. The expression of inhibin α-subunit mRNA in the estrous cycle CL (7 days after ovulation) was also examined but the level was moderately low. Considering that serum concentration of equine chorionic gonadotropin (eCG) peaks at around day 60 of pregnancy, and the expression level of inhibin α-subunit in the CL of the pregnant mare also shows a peak on day 60 of pregnancy, it was suggested that, during pregnancy in equidae, the expression of inhibin α-subunit mRNA in the CL is stimulated by eCG.

Enzyme Histochemistry of Bovine Luteinized Follicular Cysts and Corpora lutea of Estrous Cycle

Contents: Enzyme histochemical characteristics of parenchyma of luteinized follicular cysts and of corpora lutea of estrous cycle were compared in view of the developmental stages of the luteal tissue in order to evaluate the role of this type of cyst in bovine sterility. Δ5‐3β‐hydroxysteroid dehydrogenase and succinate dehydrogenase activities were higher in mature luteal tissue than in immature and regressed one. Both enzymes demonstrated higher reaction intensities in large luteal cells than in small ones. Glucose‐6‐phosphate dehydrogenase activities in non‐regressed luteal tissue specimens were higher than in regressed ones. Reaction intensities were lower in large luteal cells than in small ones. NADH2 and NADPH tetrazolium reductases exhibited very high reaction intensities compared to the other dehydrogenases demonstrated. Acid phosphatase showed an almost constantly high activity in luteal tissue irrespective of the developmental stage. Alkaline phosphatase activity was high in small luteal cells, proliferating large luteal cells, and proliferating capillary endothelial cells, as well as in fibroblasts. The present study showed enzyme histochemical characteristics of luteinized follicular cysts and corpora lutea of estrous cycle to be almost identical. Structural and enzyme histochemical findings in bovine corpora lutea of pregnancy beyond the first month of gravidity, as reported in literature, differ markedly from those described here, suggesting a similar life‐span for luteinized follicular cysts and corpora lutea of estrous cycle.Inhalt: Enzymhistochemie von Follikel‐Lutein‐Zysten und von Zyklusgelbkörpern beim Rind Enzymhistochemische Merkmale von Follikel‐Lutein‐Zysten und von Zyklusgelbkörpern wurden, bezogen auf die Entwicklungsstadien des Luteingewebes, miteinander verglichen um die Rolle dieser Zystenart im Sterilitatsgeschehen des Rindes abzuklären. Die Aktivität der Δ 5 ‐3β‐Hydroxysteroiddehydrogenase und der Sukzinatdehydrogenase waren im voll entwickelten Luteingewebe höher als im noch nicht ausgereiften oder schon in Rückbildung befindlichen. Beide Enzyme waren in den groβen Luteinzellen stärker aktiv als in den kleinen. Die Glucose‐6‐phosphatdehydrogenaseaktivität war in nicht rüekgebildeten Luteingewebeproben höher als in rückgebildeten. In den groβen Luteinzellen war die Reaktionsintensität dieses Enzyms niedriger als in den kleinen. Die NADH2‐ und die NADPH‐Tetrazoliumreduktasen waren im Vergleich zu den anderen nachgewiesenen Dehydrogenasen sehr viel stärker aktiv. Die saure Phosphatase wies unabhängig vom morphologischen Entwicklungsstadium des Luteingewebes eine fast konstant hohe Aktivität im Gewebe auf. Die alkalische Phosphatase war in den kleinen und in den proliferierenden groβen Luteinzellen sowie in sprossenden Kapillarendothelzellen und in Fibroblasten stark aktiv. In der vorliegenden Untersuchung wurde nachgewiesen, daβ die enzymhktochemisch erfaβbaren Merkmale von Follikel‐Lutein‐Zysten und Zyklusgelbkörpern nahezu identisch sind. Strukturelle und histochemische Befunde, wie sie aus der Literatur über den mehr als einen Monat alten Trachtigkeitsgelbkorper zu entnehmen sind, unterscheiden sich deutlich von den hier beschriebenen Ergebnissen. Daraus kann gefolgert werden, daβ Follikel‐Lutein‐Zysten und Zyklusgelbkörper eine ähnlich lange Verweildauer am Ovar haben.

Activity of Δ5-3 β-Hydroxysteroid dehydrogenase, succinate dehydrogenase, and glucose-6-phosphate dehydrogenase in bovine luteinized follicular cysts and corpora lutea of estrous cycle: A quantitative histochemical study

Genital organs and blood samples of dairy cows were obtained from the local slaughter-house. Fourteen luteinized follicular cysts (LFC) and 20 corpora lutea of estrous cycle (CLC) were used for the quantitative enzyme histochemical demonstration of Δ 5-3 β-hydroxysteroid dehydrogenase (3 β-OHSDH), succinate dehydrogenase (SDH) and glucose-6-phosphate dehydrogenase (G-6-PDH) activities, employing a computerized microscope photometer. Progesterone concentrations were determined in blood serum by radioimmunoassay. Luteal tissue samples were grouped in several developmental stages according to micromorphological criteria. The enzyme activities per volume unit were the same for all luteal cells regardless of their position within the cyst wall. The pattern of enzyme activities in luteal tissue was influenced by local cell composition and the fraction of steroidogenic cytoplasm in luteal tissue which varied according to the distance from the cyst cavity. In LFC and CLC, activities of 3 β-OHSDH and SDH in large (LLC) and small luteal cells (SLC) and luteal tissue, as well as relative amounts of 3 β-OHSDH-positive tissue fractions, and serum progesterone values exhibited a distinct pattern, depending on the morphological development of luteal tissue samples. G-6-PDH did not show these relations. Activities of 3 β-OHSDH and SDH were higher in LLC than in SLC. Activities of G-6-PDH, however, were distinctly higher in SLC. 3 β-OHSDH and SDH showed a positive correlation in LLC, SLC, and luteal tissue. There was no interrelation between G-6-PDH and the other enzymes tested. Enzyme activities in LLC and SLC were positively correlated. 3 β-OHSDH and SDH exhibited a positive correlation to serum progesterone concentrations, while G-6-PDH did not. The results of the present quantitative enzyme histochemical study indicate that the structural development of bovine luteal tissue of LFC and CLC is paralleled by corresponding 3 β-OHSDH and SDH activities, which, in turn, are positively related to serum progesterone concentrations. All enzymes tested are more active in LFC than in CLC, indicating a functional equivalency or almost predominance in luteal tissue of LFC compared to that of CLC. Serum progesterone concentrations, however, were lower in animals bearing LFC than in those having CLC. Since histochemical characteristics of LFC are similar to those of CLC, the results suggest that LFC regress spontaneously within a period similar to normal estrous cycle length, because no focal regeneration could be found, such as is typical for corpora lutea of pregnancy.

Pituitary regulation of corpus luteum progesterone secretion in cyclic rats.

Pituitary LH and PRL secretion during the early postovulatory period of the rat estrous cycle seem to affect the corpus luteum (CL) autonomy to secrete progesterone. Thus, while PRL would act luteotropically, LH would be luteolytic. To further investigate these facts, 4-day cyclic rats, treated with either 1 mg bromocriptine (CB) or 0.25 ml 70% ethanol (ETOH) at 1600 h on estrus, were injected with 0.5 ml of either an anti-LH serum (LHAS) or normal horse serum (NHS) at 0800 h on metestrus. Rats treated at 0800 h on metestrus with both, CB and LHAS, were also used. To verify through a different procedure the effect of LH and/or PRL deprivation in estrous cycle CL progesterone secretion, hypophysectomy (HYPOX) and sham HYPOX (SHAM) were done at 0800 h on metestrus in either CB- or ETOH-injected rats at 1600 h on estrus. Hypophysectomized rats at 1600 h on estrus were also used. Progesterone secretion was prolonged up to 0800 h on diestrus in those rats deprived of LH from 0800 h on metestrus (ETOH/LHAS, -/CB + LHAS, ETOH/HYPOX) compared with controls (ETOH/NHS, ETOH/SHAM). This luteotropic effect was absent in those rats lacking estrous afternoon PRL (CB/LHAS, CB/HYPOX, HYPOX/-). No effect on CL progesterone secretion was detected in those rats exclusively deprived of PRL on the afternoon of estrus (CB/NHS, CB/SHAM). These results suggest that in the absence of the protective effects of PRL secretion on the afternoon of estrus, rat CL become extremely sensitive to the luteolytic effects of early diestrous LH levels, and this results in 4-day estrous cycles.

Inhibition of [ 3H] prostaglandin F 2α binding to its receptors by progesterone

The specific binding of [ 3H] prostaglandin (PG) F 2α to bovine corpus luteum cell membranes was inhibited by progesterone. Progesterone Inhibition of binding was dependent on membrane protein and independent of [ 3H] PGF 2α concentrations in the medium. The lower inhibition of binding at high protein concentrations can be overcome by increasing the amounts of progesterone added. Progesterone inhibition of binding appears to be due to a decrease in the receptor number rather than a decrease in the receptor affinities. The kinetic properties (association and dissociation rates) of the remaining receptors were unchanged. The inhibition of [ 3H] PGF 2α binding was observed by preincubating the membranes with progesterone or by adding at the beginning but not during incubation. The concentrations of progesterone that inhibited binding by about 50% do occur in bovine corpora lutea of estrous cycle and pregnancy.

The control of progesterone secretion during the estrous cycle and early pseudopregnancy in the rat: prolactin, gonadotropin and steroid levels associated with rescue of the corpus luteum of pseudopregnancy.

The hormonal factors associated with converting a corpus luteum of estrous cycle into a corpus luteum of pseudopregnancy were studied by measuring LH and FSH prolactin, estradiol and progesterone levels in decapitated rats during the 4-day estrous cycle and a comparable time of pseudopregnancy (lights on 0600-0800 hr.). During the estrous cycle, prolactin, LH and FSH remained low and unchanging except on the afternoon of proestrus, when typical proestrous surges were observed. In contrast, estradiol levels began to increase on D-1, from baseline values of 7 pg/ml to approximately 15-20 pg/ml. These levels were maintained until the afternoon of D-2 when estradiol further increased to reach peak levels of 40-50 pg/ml by 0900 hr on proestrus. Estradiol then declined in relation to the increase in LH secreation and had returned to baseline by estrus. Progesterone secretion by the corpora lutea of the cycle also increased on the afternoon of D-1 and reached a maximum value of 25-30 ng/ml early on the morning of D-2. At this time, a precipitious fall in progesterone occurred, returning to baseline values of 5-1- ng/ml by 0700 on D-2 signifying the regression of the corpora lutea of the cycle. Progesterone remained low thereafter until the afternoon of proestrus when levels increased in response to the proestrus when levels increased in response to the proestrous surge of LH. Following cervical stimulation at 1900 hr on proestrus, no differences were noted, with respect to the estrous cycle, in LH, FSH or estradiol secreation through the afternoon of D-2. Surprisingly, progesterone levels did not differ in the cycle and pseudopregnancy until the early morning of D-29 instead of progesterone levels falling to baseline as they had during the cycle, the corpora lutea of pseudopregnancy were rescused, progesterone increasing dramatically to reach levels of 45-50 ng/ml by 1700 hr on that same day. The only difference in hormone secretion that was noted which could account for this marked divergence in progesterone secretion was the pattern of prolactin secretion following cervical stimulation. In contrast to the low levels seen during the estrous cycle, biphasio surges of prolactin secretion occured each day, one being nocturnal (0100-0900 hr) and the other diurnal (1500-2100 hr). The rescue of the corpus luteum occured in association with the nocturnal surge on D-2. These results suggest that nocturnal surge on D-2, PROLACTIN IS THE MAJOR Luteotropic stimulus which transforms and estrous cycle into pseudopregnancy by prolonging progesterone secretion from the corpus luteum. Moreover, if LH is important for progesterone secretion, no changes were observed in the pattern of LH secretion which can account for the rescue of the corpus luteum.