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Animal Breeding and Genetics
Asian-Australasian Journal of Animal Sciences 2002;15(7): 949-956.
DOI: https://doi.org/10.5713/ajas.2002.949    Published online January 1, 2002.
Role of Calcium and Calcium Channels in Progesterone Induced Acrosome Reaction in Caprine Spermatozoa
P. R. Somanath, K. K. Gandhi
Abstract
There are several physiological and pharmacological evidences indicating that opening of voltage dependent Ca2+ channels play a critical role in induction of acrosome reaction in mammalian sperm. We determined the intracellular free Ca2+ concentration in ejaculated goat sperm using a fluorescent, Ca2+ specific probe, Fura2/AM, after the suspension of sperm in KRB medium, capable of sustaining capacitation and the acrosome reaction. We used nifedipine, D-600 and diltiazem, the Ca2+ channel antagonists belonging to the classes of dihydropyridines, phenylalkylamines and benzothiazepines, to investigate the possibility that L type voltage gated Ca2+ channels play a role in the progesterone-stimulated exocytotic response. Progesterone promoted a rise in intracellular Ca2+ in goat sperm and addition of nifedipine (100 nM) just prior to progesterone induction, significantly inhibited both intracellular Ca2+ rise and exocytosis suggesting that Ca2+ channels are involved in the process. However, the intracellular Ca2+ increase during the process of capacitation was not affected with the addition of nifedipine suggesting a role of focal channel for Ca2+ during capacitation. Studies using monensin and nigericin, two monovalent cation ionophores showed that an influx of Na+ also may play a role in the opening of Ca2+ channels. These results strongly suggests that the entry of Ca2+ channels with characteristics similar to those of L type, voltage-sensitive Ca2+ channels found in cardiac and skeletal muscle, is a crucial step in the sequence of events leading to progesterone induced acrosome reaction in goat sperm.
Keywords: Goat Sperm; Nifedipine; Monensin; Nigericin; Ca2+ Channels; Fura 2


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