Daily Measurement of Pituitary Lh Content During Pregnancy in the Rat: Do Cyclic Changes Persist?

Abstract

Daily measurements of pituitary lh content during pregnancy in the rat, by the ovarian ascorbic acid depletion method, reveal no evidence of the regular changes manifested during the non-pregnant oestrous cycle. Instead, lh content rises from typical oestrous values on Day 1 to levels characteristic of cyclic pro-oestrus on Day 8. Pituitary lh content then exceeds pro-oestrous levels throughout the remainder of pregnancy until Day 21. Ovarian weight first decreases up to Day 10, then rises until the end of pregnancy. Ovarian histology reveals the presence of follicles of all sizes on each day, accompanied by increasing size of the corpora lutea of pregnancy. The significance of these observations and previous data in the literature concerning the pituitaryovarian axis during pregnancy are discussed from the point of view of the question of persistence of some manifestations of the oestrous cycle during pregnancy.

Morphometric analysis of follicular dynamics in pregnant and pseudopregnant rats

“…A low tonic secretion of LH is assumed to cause this dioestrous follicular growth (Bogovich et al, 1981). It is not within the scope of this quantitative morphological study to discuss the hormonal situation in relation to follicular development in rats in the pregnant state, since this has already been extensively discussed by Schwartz & Tally (1968).…”

“…During these prolonged dioestrous states inhibition of oestrus and ovulation occurs although enough evidence has been found to assume that follicular growth continues (Asami, 1920;Evans & Swezy, 1931;Ingram, 1962;Schwartz & Tally, 1968;Pedersen & Peters, 1971;Greenwald, 1978). However, there is still no agreement about the presence or absence of cyclic follicular maturation during these dioestrous periods.…”

Follicular Growth: The Basic Event in the Mouse and Human Ovary

“…The numbers of antral follicles were comparable to those found during the oestrous cycle until the 12th day of pregnancy, when their number increased sharply. A con¬ tinuous growth of follicles of all sizes is reported in the rat during pregnancy (Schwartz & Talley, 1968). Govan (1968Govan ( , 1970 (Krarup et al, 1969).…”

Luteinizing hormone, prolactin and ovarian 20 alpha-hydroxysteroid dehydrogenase activities during pregnancy or pseudo-pregnancy in the rat

“…Other investigators have reported pituitary LH concentrations throughout pregnancy (Greenwald, 1966;Schwartz and Talley, 1968), pseudopregnancy (Schwartz and Rothchild, 1964) and on several isolated days of prolonged pseudopregnancy with hysterectomy (Labhsetwar, 1967;Christian, Yuan, and Rothchild, 1968), Their results obtained with the OAAD biossay are relatively similar to those presented here.…”