Regional effects of streptozotocin-induced diabetes on shortening and calcium transport in epicardial and endocardial myocytes from rat left ventricle.

Manal M A Smail,Lina Al Kury,Muhammad A Qureshi,Alya Arabi,Vadym Sydorenko,Jaipaul Singh,Frank C Howarth,Murat Oz,Anatoliy Shmygol

doi:10.14814/phy2.13034

Abstract

In the heart, the left ventricle pumps blood at higher pressure than the right ventricle. Within the left ventricle, the electromechanical properties of ventricular cardiac myocytes vary transmurally and this may be related to the gradients of stress and strain experienced in vivo across the ventricular wall. Diabetes is also associated with alterations in hemodynamic function. The aim of this study was to investigate shortening and Ca2+ transport in epicardial (EPI) and endocardial (ENDO) left ventricular myocytes in the streptozotocin (STZ)‐induced diabetic rat. Shortening, intracellular Ca2+ and L‐type Ca2+ current (I Ca,L) were measured by video detection, fura‐2 microfluorimetry, and whole‐cell patch clamp techniques, respectively. Time to peak (TPK) shortening was prolonged to similar extents in ENDO and EPI myocytes from STZ‐treated rats compared to ENDO and EPI myocytes from controls. Time to half (THALF) relaxation of shortening was prolonged in ENDO myocytes from STZ‐treated rats compared to ENDO controls. TPK Ca2+ transient was prolonged in ENDO myocytes from STZ‐treated rats compared to ENDO controls. THALF decay of the Ca2+ transient was prolonged in ENDO myocytes from STZ‐treated rats compared to ENDO controls. Sarcoplasmic reticulum (SR) fractional release of Ca2+ was reduced in EPI myocytes from STZ‐treated rats compared to EPI controls. IC a,L activation, inactivation, and recovery from inactivation were not significantly altered in EPI and ENDO myocytes from STZ‐treated rats or controls. Regional differences in Ca2+ transport may partly underlie differences in ventricular myocyte shortening across the wall of the healthy and the STZ‐treated rat left ventricle.

Highlights

Blood is pumped at a higher pressure in the left ventricle compared to the right ventricle
The general aim of this project was to investigate the regional effects of streptozotocin (STZ)-induced diabetes on shortening and calcium transport in EPI and ENDO from the left ventricle of rat heart
The major findings of this study were: (1) to peak (TPK) shortening was prolonged to similar extents in ENDO and EPI myocytes from STZ-treated rats compared to ENDO and EPI myocytes from controls; (2) to half (THALF) relaxation of shortening was prolonged in ENDO myocytes from STZtreated rats compared to ENDO controls; (3) TPK Ca2+ transient was prolonged in ENDO myocytes from

Summary

Introduction

Blood is pumped at a higher pressure in the left ventricle compared to the right ventricle. The electromechanical properties of ventricular cardiac myocytes vary transmurally (Campbell et al 2008, 2009; Vasil’eva and Solov’eva 2012). This may be related to the gradients of stress and strain experienced in vivo across the ventricular wall. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Objectives

Results

Conclusion