Ischemia induced alterations in sarcoplasmic reticulum ca2+-atpase
activity in rat soleus and edl muscles.
Green, H. J., N. H. McKee, A. J. Carvalho, and J. C. Dossett-Mercer.
Department of Kinesiology, University of Waterloo, Waterloo, ON,
Canada, N2L 3G1, Department of Surgery, University of Toronto,
Toronto, ON, Canada, M5S 1A8
APStracts 3:0213C, 1996.
To investigate the time dependent effects of ischemia, as modified by
muscle fiber type composition, on sarcoplasmic reticulum (SR)
function, Ca2+-ATPase activity (Total-basal) was measured in
homogenates prepared from samples obtained from rat soleus (SOL) and
extensor digitorum longus (EDL) of ischemic (I) and contralateral
controls (C). Ischemia was induced by occlusion of blood flow to one
hindlimb for periods of 1, 2 and 3h (n=10 per group). In EDL, maximal
Ca2+-ATPase activity ([mu]mol/g w.w./min) was higher (P<0.05) in
I than in C at 1h (80+/-10 vs 56.5+/-5.3) and increased progressively
with I at both 2h (88+/-4.6 vs 53.1+/-2.8) and 3h (116+/-3.8 vs
67.8+/-3.2). In contrast, in SOL, increases (P<0.05) in Ca2+
-ATPase activity with ischemia were observed at 2h (19.2+/-0.86 vs
14.0+/-0.56) and 3h (19.9+/-1.4 vs 12.4+/-0.62) but not at 1h
(10.7+/-1.5 vs 10.0+/-0.83). In both EDL and SOL, basal (Mg2+-ATPase)
was unchanged with ischemia. Based on these findings, it can be
concluded that ischemia results in an increase in the maximal SRCa2+
-ATPase activity but that the time course of the change is dependent
on the fiber type composition of the muscle.
Received 15 April 1995; accepted in final form 24 June 1996.
APS Manuscript Number C196-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96