Progesterone-induced calcium influx in cynomolgus monkey (Macaca fascicularis) spermatozoa

For in vitro capacitation to occur in cynomolgus monkey (Macaca fasciculari s) spermatozoa, there is an absolute requirement for exogenous stimulation with the sperm activators, caffeine (1 mM) and db-cyclic adenosine monophos phate (dbcAMP) (1 mM), which are known to induce capacitation-related hyper activated motility. Tyrosine phosphorylation of sperm tail proteins is an i ntegral component of this caffeine- and dbcAMP-stimulated hyperactivated mo tility. In both capacitated and noncapacitated human spermatozoa, progester one (P-4) has been reported to elicit an immediate, potent increase in intr acellular calcium ion concentrations [Ca2+](i). The objective of this study was to examine the effects of progesterone on requisite events in macaque fertilization, including [Ca2+](i), hyperactivated motility, and the concom itant tyrosine phosphorylation of sperm tail (STTP) proteins after treatmen t with caffeine and dbcAMP. The effect of 1)LM of progesterone on [Ca2+](i) was determined by spectrofluorometry with the fluorescent indicator, fura- 2/ AM, on hyperactivated motility using computer analysis (HTM-IVOS) with t he sorting criteria lateral head amplitude (greater than or equal to 8.0 mu m), curvilinear velocity (greater than or equal to 150 mu m/s), linearity (greater than or equal to 60%), and on STTP by immunocytochemistry. The res ults showed that progesterone elicited a significant increase in [Ca2+](i) in caffeine- and dbcAMP-activated macaque sperm with maximal stimulation at 30 minutes after activation. The response in nonactivated sperm was dramat ically reduced compared with the response in activated sperm. Basal [Ca2+]( i) increased as a function of time in both activated and nonactivated contr ol sperm although basal levels were significantly increased in activated sp erm. Progesterone stimulation resulted in a small but significant increase in both hyperactivation and STTP when sperm were first pretreated with caff eine and dbcAMP. Our results provide evidence that macaque sperm activation with caffeine and dbcAMP is required for a progesterone-elicited response, which results in calcium influx, hyperactivated motility, and sperm tail t yrosine phosphorylation.