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Mechanisms of sex differences in rat cardiac myocyte response to β-adrenergic stimulation

2002; American Physical Society; Volume: 282; Issue: 1 Linguagem: Inglês

10.1152/ajpheart.2002.282.1.h256

1522-1539

Vida Vizgirda, Gordon M. Wahler, Korie Sondgeroth, Mark T. Ziolo, Dorie W. Schwertz,

Cardiac Ischemia and Reperfusion

The purpose of this study was to investigate sex differences in the functional response of isolated rat heart ventricular myocytes to β-adrenergic stimulation and in isoproterenol-stimulated signal transduction. Fractional shortening was measured using a video edge-detection system in control- and isoproterenol-stimulated myocytes that had been isolated from weight-matched rats. Number and affinity of the β-adrenergic receptors and the L-type Ca 2+ channel were measured in ventricular cardiac membranes by radioligand binding studies. Control- and isoproterenol-mediated alteration in Ca 2+ current density ( I Ca ) was determined by patch clamping and cellular cAMP content was determined by radioimmunoassay. Study results demonstrate that female myocytes have higher Ca 2+ channel density and greater I Ca than male myocytes. However, isoproterenol elicits a greater β-adrenergic receptor-mediated increase cell shortening, I Ca and cAMP production in male myocytes. Male myocytes were also found to have a higher β-adrenergic receptor density. These results suggest that cardiac myocytes from male rats have an enhanced response to β-adrenergic stimulation due to augmented β-adrenergic signaling that results in a greater transsarcolemmal Ca 2+ influx.