Characterization of ion currents elicited by a stream of fluid during spontaneous and ligand-induced chloride current oscillation in Xenopus laevis oocytes

Abstract

 During Ca²⁺-activated C^– current oscillations a mechanical deformation of the Xenopus laevis oocyte by a fluid stream evokes transient inward currents of high amplitude (stream evoked inward current, I _i,st). This current can be observed either in native or RNA-injected oocytes expressing ligand-controlled ion channels from rat brain. I _i,st reversed at the equilibrium potential of chloride and was blocked by 9-anthracene carboxylic acid (2 mM). Power spectral analysis of the oscillations did not reveal a correlation between the features of the oscillations and the amplitude of I _i,st. Antagonists of stretch-activated cation channels [gadolinium (100 µM) and lanthanum (1mM)] did not block I _i,st. Calcium channel blockers [cobalt and manganese (10 mM)] did not inhibited I _i,st and I _i,st could also be elicited in calcium-free medium. Preloading oocytes with pertussis toxin (PTX) for 17 h prevented current oscillations and I _i,st caffeine (10 mM), an antagonist of the liberation of calcium from intracellular stores, inhibited I _i,st. Our results proride evidence for modulation of the mechanosensitivity of chloride currents by activation of intracellular second messenger cascades.