Forskolin stimulates swelling-induced chloride current, not cardiac cystic fibrosis transmembrane-conductance regulator current, in human cardiac myocytes
Abstract
Whole-cell patch clamp was used to look for cystic fibrosis transmembrane-conductance regulator (CFTR)-like chloride currents in calcium-tolerant human cardiac myocytes. Potassium-containing solutions were used initially. Steady state currents were measured with hyperpolarizing ramps (-16.25 mV/s). Peak net inward currents during voltage steps from -50 to +5 mV were used as an index of L-type calcium current. Isoproterenol (1 mumol/L) or forskolin (10 mumol/L) were used in attempts to evoke CFTR-like chloride current. No forskolin- or isoproterenol-induced steady state current was found in any of 17 atrial cells from seven patients in the absence of cell swelling. Every cell exhibited a large increase in net inward current in response to forskolin, suggesting that cAMP-dependent stimulation of L-type calcium current was present. Swelling with osmotic stress induced an outwardly rectifying steady state current with a reversal potential close to the chloride equilibrium potential. Once this current was activated, exposure to forskolin caused a further increase that subsided on washout (four of four cells, two patients). The atrial swelling-induced current was studied in more detail by using cesium-containing solutions. The curren...Continue Reading
References
Inhibitory action of furosemide on the active chloride transport of papillary heart muscle in rabbit
Citations
Estrogen regulation of duodenal bicarbonate secretion and sex-specific protection of human duodenum.
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