Cyclic AMP and calcium modulated ATPase activity in the salivary glands of the lone star tick Amblyomma americanum (L.)

Abstract

Na +,K +-activated ATPase activity in tick salivary glands increases during the rapid stage of tick feeding paralleling similar increases in dopamine and cAMP-stimulated fluid secretion. High concentrations of cyclic AMP increase Na +,K +-ATPase activity in a plasma membrane-enriched fraction from the salivary glands of rapidly feeding ticks. Cyclic AMP-dependent protein kinase inhibitor protein blocks activation of Na +,K +-ATPase activity at low but not high concentrations of cAMP indicating that both activator and inhibitor modulator phosphoproteins of Na +,K +-ATPase activity exist in the plasma membrane-enriched fraction. ATPase activity in the plasma membrane-enriched fraction is not measurable in the absence of Mg 2+, Ca 2+ and Na +. Ca-stimulated nucleotidase activity is highest with ATP serving as the preferred substrate in a series including CTP, UTP, GTP and ADP. Calcium, Mg 2+ stimulated ATPase activity is activated further by calmodulin and partially inhibited by low concentration of vanadate, trifluoperazine and oligomycin. Results suggest that the plasma membrane-enriched fraction of tick salivary glands contains both Ca 2+-ATPase activity and oligomycin-sensitive Ca 2+, Mg 2+-ATPase activities, the latter likely from a small amount of mitochondria in the partially purified organelle fraction.