Measurements of intrafollicular pressures in the rabbit ovary

Abstract

Pressures within rabbit Graafian follicles have been determined by direct cannulation with micro-pipettes. The average pressure in the antrum of 60 maturing follicles was slightly over 17 mm Hg. There was no difference in the pressures in precoital and postcoital follicles. The average pressure of 15 blood follicles (preatretic) was 50 mm Hg. A direct proportionality was observed between the blood pressure and follicle pressure, suggesting that colloid osmotic pressure contributes little to the total hydrostatic pressure in the follicle. Blebbing preceded the appearance of the ovulation cone. In six measurements made during ovulation, intrafollicular pressure dropped instantly from about 15 to 5 mm Hg at the time of rupture. Visible muscle-like contractions of the follicle, concomitant with recorded pressure changes, were seen in two of six ovulating follicles. A hypothesis explaining the mechanism of ovulation includes the concept that structural changes in the thecal wall result in ballooning and the appearance of an ovulation cone. Rupture of the ovulation cone occurs under the force of a steady pressure in the antrum.