Adenylyl Cyclase System of the Small Preovulatory Follicles of the Domestic Hen: Responsiveness to Follicle-Stimulating Hormone and Luteinizing Hormone 1

Abstract

It was determined if the granulosa cells of the small preovulatory follicles of the domestic hen are a target tissue for FSH. The 3rd largest (F3), 4th largest (F4) and 5th largest (F5) follicles were removed from hens at 20, 12, 6 and 2 h before ovulation of the F1 follicle. Basal, FSH- and luteinizing hormone (LH)-stimulable adenylylatecyclase (AC) activities were measured in the granulosa cells. Isolated granulosa cells of the F5 follicle, obtained 20 h before ovulation of the F1 follicle, were incubated with ovine (o) or turkey (t) FSH and progesterone (P4) was assayed in the medium. Basal AC activity was similar for F5, F4 and F3 granulosa cells except for an increase (P < 0.01) in F3 follicles removed 2 h before ovulation of the F1 follicle. The FSH-stimulable AC activity of F5, F4 and F3 granulosa cells was elevated over basal (P < 0.01). The greatest responsiveness was seen in the F5 follicle and the least in the F3 follicle. LH-stimulable AC activity was absent in the F5 follicle but present in the F4 and F3 follicles with the greater responsiveness in the F3 follicle. Isolated F5 granulosa cells secreted significant amounts of P4 in response to oFSH and tFSH. FSH stimulates the AC system of granulosa cells of the smaller preovulatory follicles (F5 > F4 > F3) while LH stimulates the AC system of granulosa cells of the larger follicles (F3 > F4) and FSH promotes P4 production by granulosa cells of F4 follicles. The smaller preovulatory follicles of the domestic hen are a target tissue for FSH. During follicular maturation in the domestic hen, the responsiveness to FSH decreases with a concomitant increase in responsiveness to LH.