Effect of Follicular Fluid Proteins and Gonadotropins on Progesterone Secretion by Buffalo Granulosa Cells In vitro

Abstract

In the mammalian ovary the follicular fluid contains proteins and peptides which play an important role in growth, development and maturation of oocytes. The gonadotropins and some other factors work synergistically and regulate ovarian functions. In the present study the effect of follicular fluid proteins (FFP) and gonadotropins on progesterone secretion by granulosa cells (GC) from buffalo ovary, was investigated during culture. The follicular fluid was collected from small (<5 mm), and medium (5-8 mm) follicles obtained from buffalo ovaries. The follicular fluid from medium follicles was fractionated with ammonium sulphate at 80% saturation. The precipitated protein fraction was further resolved in to minor (peaks I, III) and major (peak II) proteins using gel filtration (Sephadex G-200). The FFP from small follicles and major FFP (peak II) at a dose of 200 μg/well, significantly stimulated progesterone secretion by pooled GC (3×10 5 cells/2 ml medium/well). The minor FFP did not show any stimulatory effect. There was a significant increase in progesterone secretion by pooled GC in presence of FFP and LH (10 ng/well), however, FSH (20 ng/well) with FFP exhibited an inhibitory effect. The major FFP and gonadotropins were also studied for their effect on progesterone production by GC isolated from medium and large size follicles. The GC from medium follicles were more responsive to FSH and FFP whereas GC from large follicles exhibited enhanced progesterone secretion with LH and FFP. These results indicated that FFP have their own stimulatory effect and also act synergistically with gonadotropins. The significantly different response shown by GC, for steroid hormone secretion, is based on their stage of growth and differentiation. The purification and characterization of such steroidogenic proteins may help in elucidating their role in growth and differentiation of granulosa cells.