Abundant expression of sodium-potassium-activated adenosinetriphosphatase alpha 1 subunit in corpus luteum of porcine ovary.

Follicular development is accompanied by the accumulation of follicular fluid. During corpus luteum formation, follicular fluid is diminished and antrum is replaced by lutein cells. These dynamic changes in fluid distribution suggest the existence of control mechanism of fluid transport and membrane permeability. One of the major factors regulating membrane permeability is the sodium-potassium-activated adenosinetriphosphatase (Na(+)-K(+)-ATPase). To elucidate the possible involvement of Na(+)-K(+)-ATPase in follicular growth and luteinization, immunohistochemical localization of Na(+)-K(+)-ATPase alpha1 subunit and enzyme activity in porcine ovary were investigated. In primordial follicles, Na(+)-K(+)-ATPase alpha1 subunit immunostaining was localized only in the oocyte and the surrounding stromal cells. In preantral follicles, immunostaining for Na(+)-K(+)-ATPase alpha1 subunit became apparent in granulosa and theca cells. As the follicle matured, the staining intensity in the oocyte, theca, and granulosa cells increased, which corresponded with the enzyme activity. Na(+)-K(+)-ATPase alpha1 subunit immunostaining became most abundant in granulosa and theca lutein cells in corpus luteum, and decreased in the regressing corpus luteum. Enzyme activity in corpus luteum was significantly higher than that in the follicles. This is the first study indicating that Na(+)-K(+)-ATPase alpha1 subunit expression is augmented in granulosa cells by follicular growth and most abundant in lutein cells in the corpus luteum, suggesting its possible involvement in corpus luteum formation.