HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 292/2/R837    most recent 00376.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Bupha-Intr, T. Articles by Solaro, R. J. Search for Related Content PubMed PubMed Citation Articles by Bupha-Intr, T. Articles by Solaro, R. J.

CALL FOR PAPERS
Sex Differences in Renal and Cardiovascular Function: Physiology and Pathophysiology

Myofilament response to Ca²⁺ and Na⁺/H⁺ exchanger activity in sex hormone-related protection of cardiac myocytes from deactivation in hypercapnic acidosis

¹Department of Physiology and Biophysics, Medicine and Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, Illinois; and ²Department of Physiology, Faculty of Science, Mahidol University, Bangkok, Thailand

Submitted 31 May 2006 ; accepted in final form 3 October 2006

Compared to sham-operated controls, myofilaments from hearts of ovariectomized (OVX) rats demonstrate an increase in Ca²⁺ sensitivity with no change in maximum tension (Wattanapermpool J and Reiser PJ. Am J Physiol 277: H467–H473, 1999). To test the significance of this modification in intact cells, we compared intracellular Ca²⁺ transients and shortening of ventricular myocytes isolated from sham and 10-wk OVX rats. There was a decrease in the peak Ca²⁺ transient with prolonged 50% decay time in OVX cardiac myocytes without changes in the resting intracellular Ca²⁺ concentration. Percent cell shortening was also depressed, and relaxation was prolonged in cardiac myocytes from OVX rats compared with shams. Ovariectomy induced a sensitization of the myofilaments to Ca²⁺. Hypercapnic acidosis suppressed the shortening of OVX myocytes to a lesser extent than that detected in shams. Moreover, a larger compensatory increase in %cell shortening was obtained in OVX myocytes during prolonged acidosis. The elevated compensation in cell shortening was related to a higher amount of increase in the amplitude of the Ca²⁺ transient in OVX myocytes. However, these differences in Ca²⁺ transients and %cell shortening were no longer evident in the presence of 1 µM cariporide, a specific inhibitor of Na⁺/H⁺ exchanger type 1 (NHE₁). Our results indicate that deprivation of female sex hormones modulates the intracellular Ca²⁺ concentration in cardiac myocytes, possibly via an increased NHE₁ activity, which may act in concert with Ca²⁺ hypersensitivity of myofilament activation as a determinant of sex differences in cardiac function.

heart; estrogen; sarcomeric proteins; sodium; proton exchanger

This article has been cited by other articles:

				B. M. Palmer, Y. Wang, P. Teekakirikul, J. T. Hinson, D. Fatkin, S. Strouse, P. VanBuren, C. E. Seidman, J. G. Seidman, and D. W. Maughan Myofilament mechanical performance is enhanced by R403Q myosin in mouse myocardium independent of sex Am J Physiol Heart Circ Physiol, April 1, 2008; 294(4): H1939 - H1947. [Abstract] [Full Text] [PDF]

				K. Denton and C. Baylis Physiological and molecular mechanisms governing sexual dimorphism of kidney, cardiac, and vascular function Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2007; 292(2): R697 - R699. [Full Text] [PDF]