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Contraction augments L‐type Ca 2+ currents in adherent guinea‐pig cardiomyocytes
Author(s) -
Rueckschloss Uwe,
Isenberg Gerrit
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.062604
Subject(s) - biophysics , chemistry , cytochalasin d , contraction (grammar) , protein kinase c , bapta , cytoskeleton , patch clamp , calcium , biochemistry , microbiology and biotechnology , intracellular , endocrinology , phosphorylation , receptor , biology , cell , organic chemistry
As integrins are thought to function as mechanoreceptors, we studied whether they could mediate mechanical modulation of the L‐type Ca 2+ channel current ( I Ca ) in guinea‐pig cardiac ventricular myocytes (CVMs). CVMs were voltage clamped with 280 ms pulses from −45 to 0 mV at 0.5 Hz (1.8 m m [Ca 2+ ] o , 22°C). Five minutes after whole‐cell access (designated as 0 min) peak I Ca was determined from a current–voltage ( I–V ) curve. Additional recordings were made after 5, 10 and 15 min. At control, I Ca was not stable, but ran down during these periods. This run‐down of I Ca was attenuated by soluble fibronectin (FN) and was changed to an enhancement of I Ca when CVMs were attached to FN‐coated coverslips. Soluble peptide containing the integrin binding sequence of FN, Arg‐Gly‐Asp (RGD motif), did not modulate I Ca ; however, I Ca increased in stimulated CVMs attached to RGD peptide‐coated coverslips. The effect was not specific to integrins, because attachment to poly‐ d ‐lysine‐coated coverslips also augmented I Ca in stimulated CVMs. Augmentation of I Ca by immobilized FN required rhythmical contraction of attached CVMs, because it was attenuated without electrical stimulation and after cell dialysis with the calcium chelator BAPTA. Furthermore, contraction‐induced augmentation of I Ca in FN‐attached CVMs was sensitive to inhibition of protein kinase C (PKC; by Ro‐31–8220), inhibition of tyrosine kinase activity (herbimycin A) and cytoskeletal depolymerization (cytochalasin D or colchicine). We attribute augmentation of I Ca to the activation of signalling cascades by shear forces that are generated when CVMs contract against attachment; in vivo similar signals may occur when CVMs contract against attachment of integrins to the extracellular matrix.