Immunocytochemical localization of albumin in ovarian follicles of fertile rats.

The purpose of this study was to investigate whether albumin (Alb) can be detected in ovarian rat granulosa cells. Using immunocytochemistry and morphometrics, the percentages of Alb-positive follicles (follicle-index), of Alb-positive granulosa cells (granulosa-index), and of strongly reacting follicles (intensity-index) were evaluated in intact and regressing follicles of different diameter groups during different stages of the estrous cycle. In intact follicles, the follicle- and the granulosa-index increased from small-sized to large-sized follicles. Although the follicle-index did not change in any group during the stages of the estrous cycle, the granulosa-index was higher during proestrus than during the other stages. Intact follicles showed a stronger immunoreactivity than regressing follicles throughout the stages of the estrous cycle. Thus, Alb may be a requirement for the control of follicle growth in fertile rats. This Alb function may be attributable to Alb binding to specific cell-membrane components followed by the intracellular uptake of Alb-bound substances.