Abnormalities of k+ and ca2+ currents in ventricular myocytes from
rats with chronic diabetes.
Wang, Dao Wu, Tatsuto Kiyosue, Sakuji Shigematsu, and Makoto Arita.
Department of Physiology, Oita Medical University, Hasama, Oita
879-55, Japan
APStracts 2:0196H, 1995.
Ionic mechanisms related to the prolongation of cardiac action
potential in rats with chronic diabetes mellitus were studied using
whole cell voltage clamp techniques. Diabetes was induced by
injection of streptozotocin (STZ, 65 mg/Kg weight) into the tail vein
and ventricular myocytes were isolated from STZ-injected rats (24-30
weeks) and from age- matched normal rats. The current densities of
transient outward current (Ito), a steady state outward current and
L-type Ca2+ current (ICa) were significantly smaller in cells from
diabetic animals. In addition, the kinetics of Ito of diabetic cells
was modified: (1) The decay of Ito was fitted well by a sum of 2
exponential components in normal cells ; there was only one (slow)
component in the diabetic cells, (2) The steady state inactivation
curve of Ito in diabetic cells shifted by 5 mV in the negative
direction, and (3) Recovery from inactivation of Ito was slower in
cells from diabetic animals. These alterations in Ito and the steady
state outward current can account for most of the action potential
prolongation heretofore documented. The decrease of ICa may possibly
be related to the depressed contraction seen in chronic diabetic
mellitus.
Received 18 November 1994; accepted in final form 20 April 1995.
APS Manuscript Number H1030-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.