Progesterone acts at the plasma membrane of human sperm

S Meizel, KO Turner - Molecular and cellular endocrinology, 1991 - Elsevier
S Meizel, KO Turner
Molecular and cellular endocrinology, 1991Elsevier
There has been increasing interest in the relationship between rapid effects of steroids and
steroidplasma membrane interaction. This laboratory has previously reported that
progesterone increases human sperm cytosolic free calcium ([Ca 2+] i) and thereby initiates
the human sperm acrosome reaction (AR) in< 1 min. Herein, to test whether progesterone
acts at the sperm plasma membrane, progesterone 3-(O-carboxymethyl) oxime: bovine
serum albumin (BSA) conjugate (free of unconjugated progesterone) was added to …
Abstract
There has been increasing interest in the relationship between rapid effects of steroids and steroidplasma membrane interaction. This laboratory has previously reported that progesterone increases human sperm cytosolic free calcium ([Ca2+]i) and thereby initiates the human sperm acrosome reaction (AR) in < 1 min. Herein, to test whether progesterone acts at the sperm plasma membrane, progesterone 3-(O-carboxymethyl)oxime: bovine serum albumin (BSA) conjugate (free of unconjugated progesterone) was added to capacitated human sperm. Fura-2 assays were used to detect < 1 min changes in [Ca2+]i, and indirect immunofluorescence was used to assay the AR occurring 1 min after stimulus addition. The conjugate increased [Ca2+]i and the AR (though less than did unconjugated progesterone). Enzyme immunoassays demonstrated that the concentrations of unconjugated progesterone in conjugate-treated sperm suspensions did not increase over those of control suspensions. Since the progesterone: BSA conjugate presumably does not cross the sperm plasma membrane, progesterone must act at that membrane to increase [Ca2+]i and the AR.
Elsevier