Influence of unilateral ovariectomy on follicular development in cycling rats

Abstract

Ovarian follicular development was analyzed in intact and unilaterally ovariectomized cyclic rats. Holtzman rats, followed for three successive cycles, were classified as 4-or 5-day animals, with estrus designated as day 1. Intact 4-and 5-day animals were killed on each day of the estrous cycle and one ovary from each animal was saved for histology and examined for normal follicles larger than 352 p, Cycling rats were unilaterally ovariectomized on day 1 and killed on each of the remaining days of the immediate estrous cycle and day 1 of the next cycle. The follicular population (normal follicles larger than 352 p ) was studied in the remaining ovary.During the estrous cycle of intact rats, there was a gradual increase in the number of follicles with a diameter of 518 to 571 p and greater; however, the totaI number of follicles ranging in size from 352 to 571 p and larger remained relatively constant. At day 5, in the 5-day cycling rat, the ovaries were depleted of follicles measuring from 395 to 570 p.Following unilateral ovariectomy on day 1, there was a temporary decrease in the number of follicles larger than 448 p. This agreed with the finding that animals semi-spayed on day 1 and injected with 20 I.U. human chorionic gonadotropin on day 2 (PM) did not ovulate, whereas intact animals ovulated an average of seven eggs after the same treatment. The remaining ovary of animals unilaterally ovariectomized on day 1 showed a significant increase by the next estrus in the number of follicles larger than 448 p.The method of compensatory ovulation in the rat involved doubling the number of large follicles which ultimately matured during the estrous cycle. This resulted from increased proliferation of smaller follicles in the course of the cycle rather than from decreased follicular atresia.

Blockade of recruitment of ovarian follicles by suppression of the secondary surge of follicle-stimulating hormone with porcine follicular field.

“…PFF-treated animals given exogenous FSH showed a significant (P < 0.05) dose-related increase in the recruitment of follicles 350-500 jim in diameter (Fig. 5) (4,5). This cohort of follicles, minus those which proceed into the later stages of atresia ( Fig.…”

“…This continued secretion of FSH has been called the "secondary FSH surge. " Reflecting the marked alterations in serum gonadotropins, between the mornings of proestrus and estrus there is also a discontinuous growth of ovarian follicles into the "pre-Graafian " size class, 390-500 gm in diameter (4,5). McClintock.and Schwartz (6) first proposed that, although the LH surge terminated the cycle in progress by inducing ovulation, the FSH secretion at proestrus initiated the recruitment of the cohort of follicles that would ovulate in the next cycle.…”

The number of oocytes and the rate of atresia in unilaterally ovariectomized mice up to 8 months after surgery

“…Studies of follicular development in the days following surgery indicate that the immediate compensatory ovulation is due to increased recruitment of preantral or early antral follicles (Hermreck & Greenwald, 1964;Peppier & Greenwald, 1970b;Chiras & Greenwald, 1978 Mandi & Zuckerman (1950, 1951 since these methods had been used in the earlier studies on mice and rats (Mandi & Zuckerman, 1951;Mandi et al, 1952;Jones & Krohn, 1960 (Mandi & Zuckerman, 1950, 1951 The present study was founded on the assumption that the increased output of eggs by the single ovary remaining after surgery could, in the long term, be controlled either by increasing the rate at which follicles leave the pool, or by reducing the number of oocytes lost by atresia. For the first of these assumptions the overall depletion of oocytes should be more rapid than in a control ovary, and this has been claimed to be the case in the rat (Mandi et al, 1952).…”

Acute Effects of Ovarian Steroids upon Follicular Growth in the Cycling Rat

“…The constancy of number of developing follicles in the cycling rat has been demonstrated by several workers (Mandl and Zuckerman, 1952;Peppier and Greenwald, 1970;Welschen and Rutte, 1971) using histological examination. The present study based on the direct measurement of isolated follicles made it possible to analyse the follicular activity with a relatively simple procedure and to provide more quantitative information on the development of follicles throughout the estrous cycle.…”