ALTERATIONS IN FOLLICULAR FUNCTION-ASSOCIATED WITH SELECTION ON OVULATION RATE IN FINN EWES

Finn ewes have been selected on ovulation rate to produce three lines with approximate ovulation rates of 5 (High), 3 (Control), and 2.5 (Lo w). The associated alterations in follicular function were investigate d in three experiments. The function of large estrogenic follicles (Ex p. 1) was assessed by measuring in vitro output of steroids and inhibi n after a 1-h culture period. Follicles from High line ewes contained fewer (P < .01) granulosa cells than follicles from Low line ewes. Est radiol output per granulosa cell and testosterone output per thecal ce ll were greater for High than for Low line follicles (P < .01 and < .0 5, respectively). In contrast, inhibin output, expressed per follicle or per granulosa cell, did not differ between lines. In Exp. 2, cell p roliferation in small follicles from the three lines was assessed afte r incubation of follicles in the presence of [H-3]thymidine and in the presence or absence of FSH. The slope of the linear regression relati ng labeling index of the granulosa cells and follicle size differed si gnificantly between High and Low lines with a significant negative coe fficient for High line and a nonsignificant positive slope in the Low line. In Exp. 3, follicular fluid and serum proteins were compared bet ween High and Low lines with 2D PAGE. A line difference was detected f or a serum protein (40 kDa, pI = 6). High line had one spot, whereas L ow line had three spots on 2D PAGE. This protein was not apolipoprotei n E. Furthermore, the pattern of lipoproteins (high-density and low-de nsity lipoproteins) in serum was similar between High and Low line she ep. The results indicate that selection for High ovulation rate was as sociated with smaller follicles that contained fewer granulosa. cells per thecal cell. Aspects of function of estrogenic follicles (estradio l but not inhibin production) were also changed by selection.