CHICKEN GONADOTROPIN-RELEASING HORMONES ENHANCE SOLUBLE AND INSOLUBLEFIBRONECTIN PRODUCTION BY GRANULOSA-CELLS OF THE DOMESTIC-FOWL IN-VITRO

Experiments were conducted in vitro to examine the effect of two chick en gonadotropin-releasing hormones, cGnRH-I ([Gln8]-GnRH) and cGnRH-II ([His5,Trp7,Tyr8]-GnRH), on fibronectin (soluble and insoluble) produ ction by chicken granulosa cells isolated from the largest (F1; about 35 mm in diameter), and third largest (F3; 15 to 20 mm in diameter) pr eovulatory follicles as well as from a pool of immature small yellow f ollicles (SYF; 6 to 8 mm in diameter). The amounts of soluble fibronec tin (fibronectin secreted into the incubation medium) and insoluble fi bronectin (fibronectin associated with cells plus fibronectin attached to culture substratum) were quantified with a specific ELISA. Fibrone ctin secreted into the incubation medium (soluble fibronectin) by unst imulated cells increased with advanced stages of follicular maturation . Addition of both cGnRH-I and -II increased the amount of fibronectin secreted into the incubation medium by all follicular cell types. The amount of insoluble fibronectin in culture wells that contained unsti mulated cells also increased with advanced stages of follicle developm ent. Both cGnRH-I and -II increased the quantity of insoluble fibronec tin by granulosa cells from all follicle types. Total (soluble plus in soluble) fibronectin production was elevated when cGnRH-I or -II was a dded to F1, F3 and SYF granulosa cells. The magnitude of cGnRH-I or -I I stimulation (percentage increase) of soluble, insoluble, or total fi bronectin production was calculated as a multiple of the unstimulated (control) value for each follicle type, and they were greatest in cell s derived from developing and immature follicles. These results indica te that homologous cGnRH-I and -II are capable of directly modulating the physiology of the avian ovary.