Initial evidence for the modification of hamster sperm Na+, K+-ATPase activity by cyclic nucleotide-mediated processes

Na+, K+-ATPase activity of homogenates prepared from cauda epididymal golden hamster sperm increased after the addition of cGMP (50 microM), monobutyryl cGMP (0.5 microM) or cGMP-dependent protein kinase (0.94 micrograms/ml). Addition of monobutyryl cAMP (0.5 microM) or purified catalytic subunit of cAMP-dependent protein kinase (1.26 micrograms/ml) inhibited the activity of the Na+, K+-ATPase. Preincubation with a partially purified preparation of cAMP-dependent protein kinase inhibitor (75 micrograms/ml) stimulated the activity of the Na+, K+-ATPase, and this stimulation was decreased by the addition of 5 microM monobutyryl cAMP. It is not yet known whether direct and/or indirect mechanisms are involved, but these results are the first to describe such opposing effects by cyclic nucleotide-mediated processes on a Na+, K+-ATPase activity.