Project: Research project

Project Details


The objective of this proposal is to elucidate the biochemical mechanism(s)
that regulate mammalian sperm motility before and during ejaculation.
Bovine caudal epididymal (CE) sperm are quiescent in CE fluid; dilution of
CE fluid or an elevation of its pH results in the initiation of sperm
motility. The cytoplasmic modulator of this motility quiescence and
initiation appears to be the intracellular pH (pHi). The first aim of this
research is to measure the change of pHi of bovine CE sperm, concomitant
with motility initiation, using a fluorescent, pH-sensitive chromophore,
carboxyfluorescein. The mechanism of action of pHi upon motility will be investigated in a
permeabilized bovine CE sperm model. The involvement of pH and selected
ionic components in motility regulation will be defined. This model is
ideal for testing our working hypothesis: that the changes in pHi act
directly upon the dynein ATPase to modulate motility. The effects of ionic
composition and certain motility inhibitors upon the pH-dependence of the
ATPase activity will also be determined. After evaluation of the model system, the dynein ATPase from bovine CE
sperm will be isolated and purified. This enzyme will be characterized
physically and its kinetic properties will be defined. The effects of pH,
ionic composition and inhibitors upon ATPase kinetics and upon the
interaction of the ATPase with microtubules and extracted flagella will be
studied. The existence of cyclic AMP-dependent phosphorylation of the
purified dynein ATPase and of a role for pH in this process will be
investigated. The possibility that calmodulin (CaM) is a component of, or
interacts with the ATPase in a calcium- and a pH-dependent manner will be
tested. The interaction of pH, cyclic AMP-dependent phosphorylation and
Ca2+/CaM upon the motility of the permeabilized sperm model will also be
evaluated. The understanding gained from these studies will be applied to human and
nonhuman primate sperm with emphasis upon male contraception and certain
cases of male infertility.
Effective start/end date9/1/828/31/89


  • National Institutes of Health


  • Medicine(all)


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