Effect of a single dose of anti‐LH‐serum at proestrus on the rat estrous cycle

Abstract

Previous studies have shown that pentobarbital administration at 2 P.M. of proestrus i n the rat blocks ovulation and the drop in pituitary LH content normally seen at estrus; these data were interpreted as indicating that the drug acted by blocking LH release. Signs of prolongation of estrogen secretion were seen in these rats and, in the absence of further treatment, ovulation occurred 24 hours later. In the present study a single dose of anti-ovine-LH-serum administered at 1 P.M. of proestrus also blocked ovulation, but did not prevent the drop in pituitary content on the morning of "estrus." Therefore, one may conclude that this blockade was the result of preventing the peripheral effects of LH on the ovary.The antiserum blockade did not produce prolongation of estrogen secretion and no rat ovulated within the next four days. During this time pituitary LH content was normal, as were ovarian and uterine weight, although large follicles, rather than recent corpora lutea, were seen in the ovary. Six rats were followed until the next vaginal cornification (by 6 days); only three of the six had ovulated by day seven.The contrast between the sequelae of pentobarbital and antiserum blockade is interpreted in the light of a new theory of regulation of reproductive cyclicity in the rat.In the rat exposed to an alternating light-dark environment (lights on 5 A.M. to 7 P.M.) the release of the ovulatory surge of LH starts after 2 P.M. on the afternoon of proestrus, as shown by timed hypophysectomy studies (Everett, '61 ; Hoffmann and Schwartz, '65a). Much evidence suggests that this release occurs as the result of two "necessary and sufficient" conditions (Schwartz and Bartosik, '62): first, there appears to be a daily facilitatory period for LH release starting after P.M. (Everett, '61); second, enhanced ovarian secretion occurs on the day before proestrus (Schwartz, '64; Schwartz and Talley, '65). However, these two conditions are not completely independent since the critical period for LH release is prolonged when steroid secretion is enhanced (Hoffmann and Schwartz, '65a,b). The LH release for ovulation can be blocked by administration of pentobarbital before 2 P.M. of the day of proestrus, as shown by the effect of pentobarbital in preventing the proestrous rise in plasma LH (Schwartz and Caldarelli, '65), the drop in pituitary LI-I content normally seen at estrus (Schwartz, '64) and, of course, the expected ovula- The present study approached the problem of ovarian-pituitary interrelationships from a different point of departure. It has been demonstrated that a single dose of anti-ovine-LH-serum, when administered before the proestrous facilitatory period, can block ovulation (Kelly, Robertson and Stansfield, '63). The purpose of the present experiment was, first, to ascertain whether the antiserum blockade was peripheral (by testing to see if pituitary LH content depleted at estrus) and, second, to follow the subsequent ovarian and pituitary events and contrast these with the effects of pentobarbital blo...

Effects of Barbiturate Injection on the Day Before Proestrus in the Rat

“…It is possible that barbiturates administered on the day before proestrus exert a partial blockade of LH release, thus reducing estrogen and progesterone secretion enough to prevent the triggering of the ovu latory surge of LH on the day of proestrus but not enough to prevent vaginal and uterine changes. (Following a single injection of anti-LI I serum at proestrus, uterine and vaginal signs of estrogen secretion returned more quickly in the next cycle than the LH release for ovu lation, suggesting that more steroid may be necessary to induce LH release than uterine and vaginal signs [Schwartz and Gold 1967]). Another possibility is that the barbiturates did not block estrogen secretion to any appreciable extent, but were blocking the gonado trophin release responsible for progesterone secretion, which may be necessary for release of the ovulatory surge of LH, when superimposed on a background of estrogen secretion [Everett and Sawyer 1949].…”

“…Some were laparotomized between 10 and 11a.m. on the following morning ("proestrus") to check the extent of uterine distention or ballooning, previous experi ments having shown that this procedure does not interfere with subsequent events leading to ovulation [Schwartz 1964;Schwartz and Gold 1967], At autopsy between 10 and 11 a.m. on the morning of expected cstrus, oviducts were inspected under the dissecting microscope for the distended, translucent area indicative of recent ovulation. In many of the obviously positive cases this ampullar segment was cut and ova were extruded and counted, or serial sections of one ovary and oviduct were prepared; in every negative or questionable case such serial sections were made.…”

Examination of the role of FSH in periovulatory events in the hamster

“…While FSH has been shown to bring about ovulation in hypophysectomized, pentobarbital-or chlorpromazine-blocked rats and in PMSG-primed immature rats (Carter et al, 1961 ;Lostroh & Johnson, 1966;Harrington, Bex, Elton & Roach, 1970;Nuti, McShan & Meyer, 1974;Tsafriri et al, 1976), endogenous FSH has not been found necessary for ovulation in any studies, including the present, in which FSH antiserum was used (Schwartz, Krone, Talley & Ely, 1973;Moudgal, Rao, Maneckjee, Muralidhar, Mukku & Sheela Rani, 1974;Jagannadha Rao et al, 1974a;Schwartz, Cobbs, Talley & Ely, 1975). The role of LH in ovulation, on the other hand, has been unequivocally demonstrated in many systems (Kelly, Robertson & Stanfield, 1963;Lostroh & Johnson, 1966;Schwartz & Gold, 1967;Sasamoto, 1969;Madhwa Raj & Moudgal, 1970;Ely & Schwartz, 1971;Moudgal, MacDonald & Greep, 1971;Jagannadha Rao et al, 1974a;Lipner et al, 1974;Schwartz et al, 1975;Tsafriri et al, 1976). It is probable that in systems in which ovulation has been induced by FSH, it is due to synergism with the minimal amounts of LH that may be found in the system (either present in the system ia low amounts, even after hypophysectomy, or as a contaminant), because FSH in combination with minimal amounts of LH has been shown to cause ovulation in hypophysectomized immature rats (Lipner et al, 1974).…”

Depression of Decidual Growth in the Rat With Lh Antiserum and Pituitary Autotransplantation

“…This was true except when lh antiserum was given on Days 1 to 5 in intact rats, indicating that antibodies can exist for several days in circulation (Quadri et al, 1966;Schwartz & (Finn, 1965). Hetherington (1968) demonstrated a difference in decidua formation following an intra-uterine injection of air compared with oil.…”