Endothelin-1 activates a Ca2+-permeable cation channel with TRPC3 and TRPC7 properties in rabbit coronary artery myocytes

In the present work we used patch pipette techniques to study the properties of a novel Ca2+-permeable cation channel activated by the potent coronary vasoconstrictor endothelin-1 (ET-1) in freshly dispersed rabbit coronary artery myocytes. With cell-attached recording bath application of 10 nM ET-1 evoked cation channel currents (I-cat) with subconductance states of about 18, 34 and 51 and 68 pS, and a reversal potential of 0 mV.ET-1 evoked channel activity when extracellular Ca2+ was the charge carrier, illustrating significant Ca2+ permeability. ET-1-induced responses were inhibited by the ETA receptor antagonist BQ123 and the phospholipase C (PLC) inhibitor U73122. The diacylglycerol analogue 1-oleoy1-2-acety1-sn-glycerol (OAG) also stimulated I-cat, but the protein kinase C (PKC) inhibitor chelerythrine did not inhibit either the OAG- or ET-1-induced I-cat. Inositol 1,4,5-trisphosphate (IP3) did not activate I-cat, but greatly potentiated the response to OAG and this effect was blocked by heparin. Bath application of anti-TRPC3 and anti-TRPC7 antibodies to inside-out patches markedly inhibited ET-1-evoked I-cat, but antibodies to TRPC1, C4, C5 and C6 had no effect. Immunocytochemical studies demonstrated preferential TRPC7 expression in the plasmalemma, whereas TRPC3 was distributed throughout the myocyte, and moreover co-localization of TRPC3 and TRPC7 signals was observed at, or close to, the plasma membrane. Flufenamic acid, Gd3+, La3+ and extracellular Ca2+ inhibited lcat with ICSO values of 2.45 mu M, 3.8 mu M, 7.36 mu M and 22 mu M, respectively. These results suggest that in rabbit coronary artery myocytes ET-1 evokes a Ca2+-permeable non-selective cation channel with properties similar to TRPC3 and TRPC7, and indicates that these proteins may be important components of this conductance.