Physiological levels of immunoreactive ANH-like peptides in human follicular fluid

The concentrations of immunoreactive C-terminal (ANH-(99-126)) and N-terminal (ANH-(1-98] portions of pro-ANH were measured in follicular fluid and plasma samples from 9 young women undergoing in vitro fertilization. ANH-(99-126) and ANH-(1-98)-like immunoreactivity levels in plasma were 6.0-25.4 (mean 12.2 pmol/l and 184-427 (mean 300) pmol/l, respectively, whereas the corresponding levels in follicular fluid were 3.8-8.0 (mean 4.9) pmol/l and 169-385 (mean 262) pmol/l. The concentrations of both ANH-like peptides were consistently lower (p less than 0.01) in the follicular fluid than in the matched plasma samples, but within the variation found in plasma controls. It is concluded that ANH-like peptides in the follicular fluid, whether secreted locally or derived from circulating ANH, might play a physiological role in the biosynthesis of ovarian steroid hormones or follicular maturation and fluid dynamics.