Influence of follicular maturation on the susceptibility of chicken ovarian granulosa cells to free oxygen radicals

Abstract

The influence of ovarian follicular maturation on lipid peroxidation-induced changes in the fluidity of plasma membrane of granulosa cells was investigated using the fluorogenic polyunsaturated fatty acid cis-parinaric acid (cPNA). An increase in lipid peroxidation results in the decrease of fluorescence intensity of cPNA. A decrease in membrane fluidity results in the decrease of fluorescence polarization of cPNA. Granulosa cells isolated from the largest (F1; mature), and third largest (F3; developing) preovulatory follicles as well as from a pool of immature small yellow follicles (SYF) of the domestic hen ovary were pre-labelled with cPNA. The cPNA-labelled cells were exposed to a free oxygen radical generating agent 2,2'azobis-(2-amidinopropane)-hydrochloride (AAPH). AAPH enhanced the rate of decrease in fluorescence intensity of cPNA-labelled cells. This effect of AAPH was greater in the more differentiated granulosa cells obtained from mature follicles than in less differentiated cells isolated from immature follicles. Similarly, the degree of change in fluorescence polarization was greater in more differentiated F1 granulosa cells than in the less differentiated ones. The analysis of fatty acid composition of phospholipids indicated that the plasma membrane of differentiated granulosa cells contained a higher proportion of the unsaturated fatty acids, oleic and linoleic acids. The fluorescence data show that the rigidity of the plasma membrane of chicken granulosa cells decreases with advancing follicular maturation presumably due to relative increase in the unsaturated fatty acid content of plasma membrane phospholipid.