Effects of Steroids on the Release of Luteinizing Hormone in the Rat

Kobayashi, Fuminori; Hara, Katsumi; Miyake, Tamotsu

doi:10.1507/endocrj1954.16.251

Cited by 27 publications

(23 citation statements)

References 8 publications

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“…Similar action of synthetic progestin was demonstrated in immature rats by Meyer (1963 and1965). Compared with the dose of progesterone which accelerated spontaneous ovulation, a huge amount of progesterone was required to restore delayed ovulation (Kobayashi et al, 1969a). Further, norethynodrel, which failed to restore delayed ovulation in our previous study (Kobayashi et al, 1969c), facilitated LH-release in 3 out of 6 rats in this study.…”

Section: Discussioncontrasting

confidence: 49%

Facilitation of Luteinizing Hormone Release by Progesterone in Proestrous Rats

1970

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SynopsisIn order to elucidate the facilitation of ovulatory release of luteinizing hormone (LH) and subsequent ovulation, subcutaneous injection or intrahypothalamic implantation of progesterone was carried out on the morning of proestrus in 4-day cyclic rats . By injecting progesterone on the morning or early afternoon of proestrus , an approximate 3 hr advancement of ovulatory release of LH was demonstrated by confirming the occurrence of ovulation on the next morning after timed hypophysectomy performed on the afternoon of proestrus. Ovulation also occurred about 3 hr earlier in the estrous morning when progesterone had been given on the morning of proestrus. The minimum effective dose of progesterone to facilitate LH-release was somewhere between 0 .1 and 0.625mg per rat. Facilitation of LH-release by steroid administration on the morning of proestrus is not entirely specific for progesterone. Norethisterone, medroxyprogesterone acetate , and desoxycorticosterone(DOC) also induced the advanced release of LH. Facilitation of ovulatory release of LH was induced also in the rats having progesterone crystals implanted in the median eminence-arcuate region of the hypothalamus on the morning of proestrus. These results indicate that a neural timing factor regulating the onset of LHrelease in proestrus is labile to a certain extent, and that it operates about 3 hr in advance when it is exposed to progesterone given on the morning of proestrus , and that the appearance of facilitatory action of progesterone depends on the pre-existing estrogen level in the circulating blood.It is well known that progesterone has a biphasic effect on ovulation and, according to the conditions, it can either stimulate or inhibit the release of luteinizing hormone (LH) (for a review see Everett, 1964; Sawyer, 1964;Rothchild, 1965;Davidson, 1969). A lack of spontaneous ovulation during pregnancy or pseudopregnancy is evidence of the inhibitory effect on LH-release of endogenous progesterone, the secretion of which is increased during gestation. Exogenous progesterone also inhibits or delays spontaneous ovulation in rats and in many other species. The stimulating effect of progesterone on ovulation has been shown under several conditions, e. g. in persistent estrous rats (Everett, 1940), in normal 5-day cyclic rats (Everett, 1948; BrownGrant, 1967) and in immature rats primed with pregnant mare's serum gonadotropin Meyer, 1963 and1965).With regard to the ovulation induction in adult rats, it was previously suggested by Everett(1948) that the appearance of stimulating action of progesterone depends on the pre-existing estrogen level in the circulating blood. In our previous work, progesterone administered into 4-day cyclic rats induced a delayed ovulation only when injected before 2 a. m. proestrus, by which time estrogen secretion had not attained the maximum (Hori et al., 1968), and it accounted for uterine distension and uterine weight increase on the day of proestrus though it was not enough for the release of LH on the same day (Kob...

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Section: Discussioncontrasting

confidence: 49%

Facilitation of Luteinizing Hormone Release by Progesterone in Proestrous Rats

1970

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“…It has been shown that the ovarian steroids responsible for the proestrous rise in uterine weight, an ovulatory surge of gonadotropin, and for estrous vaginal cornification, start to secrete on the afternoon before proestrous day (Schwartz, 1964;Lawton and Sawyer, 1968;Kobayashi et al, 1969a). Furthermore, this ovarian secretion due to gonadotropin release on the day before proestrus is also reported (Lawton and Sawyer, 1968;Kobayashi et al, 1969b).…”

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confidence: 96%

Acute Effect of Neural Deafferentation on Timing of Gonadotropin Secretion Before Proestrus in the Female Rat

Kawakami

Terasawa

1972

Endocrinol Japon

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SynopsisAn attempt was made to investigate a role of the brain on release of gonadotropin responsible for the events of proestrus and estrus in the 4-day cyclic rats. Rats were acutely deafferented at the level of anterior commissure (AC) with three kinds of the L-shaped knives at the different time of day, and autopsied to examine the uterine distension and ovulation on the days of expected proestrus or estrus. Serum and pituitary level of LH, FSH and prolactin in the deafferented rats were measured by radioimmunoassay. The results are as follows: 1) With an L-shaped knife of 2.5 mm of the horizontal blade (knife A) the fornix (Fx) and the stria terminalis (ST) were interrupted and simultaneously the tract of diagonal bundle of Broca (TDB), the bed nucleus of stria terminalis (BST), the nucleus of accumbens (ACC), the nucleus of anterior commissure (NAC) and parolfactory area were commonly damaged. The deafferentation at 20:00 on the day of diestrus I prevented vaginal cornification, uterine distension and ovulation on the expected estrous day. Full cornification was observed in all examined rats with transection after 10:00 on the day of diestrus II, while uterine distension was not observed in the rats with transection before 20:00 on the same day. None of rats bearing the transection ovulated on the day of estrus, even the transection was performed at 8:00 on the day of proestrus. 2) With an L-shaped knife of 1.4 mm of the horizontal blade (knife B) the Fx were interrupted and the BAC and the TDB were commonly damaged, however, the ST, the BST and the ACC were only partially damaged. Most of results following to the neural transection with knife B were similar to those observed with knife A except for ovulation being observed in the rats transected at 8:00 on the day of proestrus. However, transection at the mid-thalamus (knife placed at 2 mm caudal to the AC) did not interfere any normal cyclic changes. 3) Estrogen injection into the rats transected with knife B at 20:00 on the day of diestrus II resulted in inducing ovulation, while with knife A did not. 4) Transection either Fx or medial cortico-hypothalamic tract (CHT) with an L-shaped knife of 1.0 mm of the horizontal blade (knife C) on the day of diestrus I partially prevented the occurrence of events of proestrus and estrus. 5) Transection of the septal complex with knife B at 20:00 on the day of diestrus I prevented a rise of pituitary LH, pituitary prolactin and serum prolactin, which used to be observed in normal proestrus. Both Fx and CHT transection resulted in an increase of pituitary FSH. From the ovariectomy experiment the ovary of the our colony's rats must be in situ at 15:00 for vaginal cornification and at 24:00 for uterine distension. Thus, following facts are suggested 1) the septal complex or higher brain such as the limbic structure may be involved in the release of gonadotropin responsible for the events of proestrus and estrus, 2) timing of release of gonadotropin (folliculotropin) might occur preceding to the ovarian changes and it ...

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“…Pretreatment with progesterone denied the stimulative action of EB on gonadotropin release (Table 5) but did not debase the luteotropic action of estrogen (Table 6). The treatment with progesterone alone did not seem to cause an increase in ovarian secretion of progesterone, since Kobayashi et al (1969) demonstrated, using the rats in our breeding conditions, that progesterone treatment on estrus or diestrus 1 does not affect the timing of ovulation, while the treatment on diestrus 2 does delay ovulation by 48 hr. These results suggest that although prolactin possesses luteotropic action (MacDonald et al, 1970;Armstrong et al, 1970;Uchida et al, 1970) and LH is also required for the maintenance of corpora lutea (Loewit et al, 1969;Madhwa Raj and Moudgal, 1970;Yoshinaga et al, 1971), either gonadotropin, alone or combined, is unable to mediate the luteotropic action of estrogen.…”

Section: Discussionmentioning

confidence: 64%