Hydrogen hexachloroplatinate induces the acrosome reaction in human spermatozoa

Human spermatozoa from healthy donors (n = 7) were washed in Tyrode's medium containing 0.6 mg/ml freeze-dried egg yolk, filtered through glass wool and exposed to 0.5, 5, 50, 500 or 1000 microM hydrogen hexachloroplatinate. Viability, membrane integrity and the acrosome reaction were examined using trypan blue exclusion, hypo-osmotic swelling test and fluoresceinated Pisum sativum agglutinin, respectively, after incubation for 3 or 6 h at 37 degrees C. While sperm motility, viability and membrane integrity were not affected by the platinum compound after incubation for 3 h, the number of acrosome-reacted spermatozoa increased from 16.0 +/- 6.4% (control, mean +/- SEM) to 21.0 +/- 3.3 (0.5 microM), 22.3 +/- 4.3% (5 microM), 28.0 +/- 4.3% (50 microM, p < 0.01), 29.3 +/- 3.9% (500 microM, p < 0.01) and 43.9 +/- 7.4% (1 mM, p < 0.001); a further increase was detected after incubation for 6 h. However, the percentages of dead and immotile spermatozoa and those with defective membranes were also higher, suggesting that the acrosome reaction was caused by degenerative processes after long-term incubation. In conclusion, hydrogen hexachloroplatinate does not affect sperm motility, membrane integrity or viability, but it does induce the acrosome reaction after incubation for 3 h before cytotoxic effects are measurable. Similar effects of halide salts of platinum on receptor-mediated exocytosis have been described in other cells such as mast cells and basophils in vivo and in vitro.