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. 1994 Mar 15;91(6):2367–2371. doi: 10.1073/pnas.91.6.2367

Ca2+ influx through stretch-activated cation channels activates maxi K+ channels in porcine endocardial endothelium.

J Hoyer 1, A Distler 1, W Haase 1, H Gögelein 1
PMCID: PMC43372  PMID: 7510889

Abstract

The endocardial endothelium is an important modulator of myocardial function. The present study demonstrates the existence of a stretch-activated Ca(2+)-permeable cation channel and of a Ca(2+)-activated K+ channel in the endocardial endothelium of the porcine right atrium. The stretch-activated channel is permeable for K+, Na+, Ca2+, and Ba2+, with mean conductances of approximately 32 pS for the monovalent cations and approximately 13 pS for divalent cations. The Ca(2+)-activated K+ channel has a mean conductance of 192 pS in symmetrical KCl. solution. Channel activity is strongly dependent on membrane potential and the cytosolic Ca2+ concentration. Half-maximal activation occurs at a cytosolic Ca2+ concentration of approximately 5 microM. The influx of Ca2+ through the stretch-activated channel is sufficient to activate the Ca(2+)-activated K+ channel in cell-attached patches. Upon activation of the stretch-activated channel, the cytosolic Ca2+ concentration increases, at least locally, to values of approximately 0.5 microM, as deduced from the open probability of the Ca(2+)-dependent K+ channel that was activated simultaneously. The stretch-activated channels are capable of inducing an intracellular Ca2+ signal and may have a role as mechanosensors in the atrial endothelium, possibly activated by atrial overload.

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