Biochemical and structural differences between porcine ovarian follicular and luteal mitochondria.

Abstract

Mitochondria from intact follicles (6-10 mm) and corpora lutes of porcine ovaries were isolated and compared biochemically and structurally. With succinate as substrate, luteal mitochondria consumed oxygen at a rate four times greater than did follicular mitochondria. However, the ADP:O ratio (moles of ADP converted to ATP per atom of oxygen) was significantly lower in luteal mitochondria. Follicular mitochondria synthesized 8.9 pmoles ATP/mg protein/2 h, whereas luteal mitochondria synthesized 21.2 �moles/mg protein/2 h. Also, luteal mitochondria converted five times more (4�I4 Cl -cholesterol to l4-’� Cl -pregnenolone than did follicular mitochondria. The amounts of cytochrome aa3 in follicular and luteal mitochondria were 0.052 and 0.15 nmoles/ mg protein, respectively, while the amounts of cytochrome P450 were 0.011 and 0.21 nmoles/mg protein. Electron microscopic examination of nonsectioned isolated samples showed that luteal mitochondria were significantly larger than follicular mitochondria, It is concluded that luteal mitochondria are more active in steroidogenesis and energy production than are follicular mitochondria. These higher levels of activity in luteal mitochondria probably result, in part, from the presence of additional functional components as indicated by increases in mitochondrial size and amounts of cytochrome aa3 and cytochrome P450.