Reductions in sarcoplasmic reticulum Ca²⁺ ATPase activity in rat skeletal muscles of different fibre composition with ischemia and reperfusion

Abstract

To investigate the significance of fibre type and the duration of ischemia on changes in sarcoplasmic reticulum Ca2+ ATPase activity (SR Ca2+ ATPase), blood flow was occluded to the rat hind limb for 1, 2, or 3 h (n = 10 per group) and the soleus and extensor digitorum longus (EDL) muscles were examined following 2 h of reperfusion. When compared with the contralateral control muscles, calcium-dependent (total tau basal) SR Ca2+ ATPase activity in soleus was reduced (p < 0.05) to 75.9% by 1 h of ischemia and 2 h of reperfusion (13.1 +/- 0.6 vs. 9.95 +/- 0.85 mumol.mg-1 wet weight.min-1; X +/- SE) with no further reduction (p > 0.05) observed at either 2 h (9.75 +/- 0.57) or 3 h (9.40 +/- 0.64) of ischemia and 2 h of reperfusion. For the EDL muscles, SR Ca2+ ATPase activity with 2 h reperfusion was not reduced (p > 0.05) with 1 h of ischemia (80.4 +/- 3.0 vs. 70.7 +/- 2.9 mumol.mg-1 wet weight.min-1) but was reduced (66.7 +/- 2.3 mumol.mg-1 wet weight.min-1; p < 0.05) in the 2-h ischemia group, with further reductions (53.2 +/- 3.4 mumol.mg-1 wet weight.min-1; p < 0.05) in the 3-h ischemia group. No changes (p > 0.05) in basal or SR Mg2+ ATPase were found for either muscle group with ischemia and reperfusion, regardless of the duration of ischemia. When these results are interpreted in the context of the increases in SR Ca2+ ATPase activity that occur with ischemia, it appears that two components are involved in the reductions in SR Ca2+ ATPase activity noted during reperfusion: one that reduces the SR Ca2+ ATPase activity to below normal and one that simply reverses the ischemic-induced increase in SR Ca2+ ATPase activity. The former component appears to be more pronounced in the EDL muscle.

Postcontractile force depression in humans is associated with an impairment in SR Ca2+pump function

“…Both of these are considered primary factors responsible for ischemia-reperfusion injury in skeletal muscle (32). Ischemia and reperfusion also lead to reduced Ca 2ϩ -ATPase activity in vitro in rats (20).…”

“…Calcium uptake rates in homogenates of human muscle are maximal at this [Ca 2ϩ ] f (unpublished). These procedures represent a modification from those previously employed in our laboratory (20).…”

Changes in skeletal muscle sarcoplasmic reticulum function and force production following myocardial infarction in rats

“…It is possible that chronic underperfusion may trigger some to the changes in SR function shown here. Indeed, ischaemia has recently been shown to alter skeletal muscle SR function (Green, McKee, Carvalho & Phillip, 1997). However, chronic alterations in blood flow such as those induced by femoral artery stenosis do not produce alterations in force production and fatigue kinetics such those observed following MI (Mathien & Terjung, 1986;Yang, Ogilvie & Terjung, 1991).…”

Cation pumps in skeletal muscle: potential role in muscle fatigue.

“…However, the increase in Ca 2+ ‐ATPase activity does not appear to depend on contractile activity since we have been able to demonstrate time‐dependent increases in both fast and slow rat muscle with ischaemia (Green et al. 1996a), an effect which is reversed with reperfusion (Green et al. 1996b).…”