Hypophysectomy in the pregnant rat

Abstract

TWO TEXT FIGWS AND TWO PLATES (FOUR FIGURES)I n a preliminary report (Pencharz and Long, '31) on the effect of hypophysectomy in the pregnant rat, it was stated that removal of the anterior and posterior portions of the gland between the eleventh and twentieth days of pregnancy was followed by a lengthening of the gestation period by from 3 to 4 days. On the other hand, in those instances in which fragments of the gland had been inadvertently left behind, gestation was normal or disturbed, depending upon the amount of tissue left in situ. Since that announcement, experiments have been extended to include earlier stages of pregnancy, and the present paper is a detailed report of the earlier observations and of the more recent studies.I n the paper referred to above it mas also stated that in those instances in which the operation was complete and no tissue could be detected at autopsy and by serial sections of the pituitary region, the rats died at the end of a prolonged gestation period without being able to expel their young, In the more recent studies a number of animals survived, dead and living young being born several days beyond term.So far as the writers are aware, the literature contains an account of only two short series of experiments dealing with the effects of total hypophysectomy in the pregnant animal, The first group of experiments was carried out by Aschner in 1912 on three pregnant dogs, in which ablation of the hypophysis was followed by abortion in from 3 to 12 days. after the operation.

The Size of the Corpus Luteum during Pseudopregnancy and Pregnancy in the Rat

“…Hypophysectomy before the 11th day invariably terminated pregnancy in the rat. However, after the 12th day pregnancy was maintained, evidently because the placenta secreted a luteotrophic hormone in sufficient amount by this time (Alloiteau, 1957 ;Rothchild 1960 ;Astwood and Greep, 1938 ;Pencharz and Long, 1933). Presence of prolactin-like hormone in the rat placenta which had a luteotrophic effect has been reported (Astwood and Greep, 1938;Averil et al, 1950, Ray et al, 1955.…”

Luteotrophic Activity of the Young Conceptus in the Rat

“…Under our conditions the Day-8 conceptus was already sufficiently active to maintain pregnancy in some rats. It is interesting that the Day-8 placenta has also some mammotrophic activity (Ray, Averill, Lyons & Johnson, 1955). As hypophysectomy interrupts pregnancy when performed before Day 12, pregnancies maintained after the cessation of progesterone treatment in our experiment were also considered to be supported by the pituitary.…”

“…Concerning the maintenance of the corpora lutea, there is abundant evi¬ dence that the placenta plays an important role during the latter half of pregnancy (Pencharz & Long, 1933;Klein, 1935;Astwood & Greep, 1938; Deanesly & Newton, 1941 ; Averill, Ray & Lyons, 1950). Although it has been established that the maintenance of the corpora lutea during the first half of pregnancy is dependent on pituitary luteotrophic activity, Alloiteau (1957) was able to demonstrate that the young conceptus could also maintain the corpora lutea in rats hypophysectomized just after implantation, provided that the pregnancy was supported by daily injections of progesterone.…”

Expression of LH-.ALPHA. and -.BETA.Subunit mRNAs in the Rat Placenta.

“…The existence of gonadotropic activity in rat and mouse placenta was demonstrated in early studies done in the 1930s by Pencharz and Long [8] and Astwood and Creep [9]. Gonadotropin-like activity has been found in serum from pregnant rats [10,11], but an antibody to the rat LH (rLH)-a subunit was unable to detect the a subunit in rat placenta [12], and no detectable specific mRNAs have been found by northern blot analysis [13].…”