COMPARISON OF THE ABILITY OF PROGESTERONE AND HEAT SOLUBILIZED PORCINE ZONA-PELLUCIDA TO INITIATE THE PORCINE SPERM ACROSOME REACTION IN-VITRO

It has been previously shown that progesterone can initiate the acroso me reaction (AR) of capacitated human and hamster sperm in vivo. We re port here that progesterone can initiate a morphologically normal AR i n porcine sperm that have undergone capacitation in a Hepes-buffered m edium in vitro. In addition, we have compared the abilities of progest erone and heat-solubilized porcine zona pellucida (zona) to initiate t he porcine sperm AR. Capacitated porcine sperm were treated with 1 mu g/ml progesterone, 150 mu g/ml porcine zona, or solvent control for 10 min. After treatment, sperm were incubated with the supravital dye Ho echst 33258, fixed and the acrosomal status determined in the previous ly viable sperm by fluorescence microscopy with fluorescein isothiocya nate-labeled Pisum sativum agglutinin (FITC-PSA). There was no signifi cant difference between the percentage of AR initiated by zona compare d to that initiated by progesterone. In order to determine whether the re was a synergistic interaction between the two AR initiators, both w ere added simultaneously to capacitated porcine sperm at optimal (1 mu g/ml progesterone, 150 mu g/ml zona) and suboptimal (75 ng/ml progest erone and 75 mu g/ml zona) concentrations. Simultaneous addition of th e two AR-initiators at the two concentrations stimulated an additive A R-initiating response, rather than a synergistic one. Several possible explanations for the additive results are discussed. (C) 1994 Wiley-L iss, Inc.