The long range goals of this project are to elucidate the metaregulatory mechanisms that maintain the resting internal ionic mileau of sperm and alter it in response to those instructive signals that coordinate sperm capacitation (the obligatory, terminal maturational sequence that prepares sperm for fertilization). The more complete understanding of the processes that control crucial cellular functions in sperm, gained from these studies, will allow more selective and effective intervention in the palliative sense required for some clinical infertility and the preventative sense required for sperm-directed antifertility measures.
The specific aims of this project are: to determine the mechanisms that function in maintaining resting internal. [Ca++] and pH in sperm (with particular attention to anion [Cl-] and cation [Ca++,K+] channels and to Na+/H+ and Na+/Ca++exchange activities); to depict the temporal and spatial relationships of the elevations of pHi and Cai associated with the zona-induced acrosome reaction; to describe the ion channels, exchangers or pumps operating in these agonist-induced ionic alterations; to delineate the electrophysiological characteristics of sperm membrane ion channels; to define the role of GTP binding regulatory proteins (G proteins) in these processes; to demonstrate the function of a peptide component of seminal plasma that possibly modulates these actions of G proteins. Some powerful new tools are available for achievement of these goals. A variety of fluorescent probes now provide continous, sensitive and specific means for determination and monitoring of intracellular pH, [Ca++],[Cl-] and [Na+] and membrane potential of intact sperm. Video fluorescence imaging allows examinations of individual cells and of changes within localized subcellular compartments. Electrical recordings from mixed proteolipid membranes provide direct measure of single channel conductances and determination of the ion selectivity, voltage dependence, of individual ion channels (or exchangers) and the actions of their modulatory effectors. By a coordinated application of these biophysical and biochemical methods we will more completely describe the bases of homeostasis and metaregulatory control in experiments that identify and systematically examine requirements for operation of molecular components and by examination of their responses to a physiological agonist of mammalian sperm exocytosis and a peptide component of sperm with putative modulatory effector activity.
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