RESUMO
<p><b>OBJECTIVES</b>To investigate the localization and positive percentage of progesterone receptor (PR) on the human sperm surface.</p><p><b>METHODS</b>After in vitro capacitation, progesterone binding sites on the sperm were quantitatively analyzed by fluorescence microscopy and flow cytometry using fluorescein isothiocyanate-labeled bovine serum albumin-progesterone complex (P-BSA-FITC).</p><p><b>RESULTS</b>The spermatozoa stained by P-BSA-FITC mainly showed two labeling patterns, with the green fluorescence on the whole acrosomal region or the equatorial acrosomal region only and the stainless postacrosomal and tail regions. The percentage of progesterone-binding sperm was (30.2 +/- 2.4)%.</p><p><b>CONCLUSIONS</b>There is selective expression of PR on the human sperm acrosome surface.</p>