title: Effects of 4-h ischemia and 1-h reperfusion on rat muscle sarcoplasmic reticulum function.
abstract: To investigate the hypothesis that ischemia and reperfusion would impair sarcoplasmic reticulum (SR) Ca(2+) regulation in skeletal muscle, Sprague-Dawley rats (n = 20) weighing 290 +/- 3.5 g were randomly assigned to either a control control (CC) group, in which only the effects of anesthetization were studied, or to a group in which the muscles in one hindlimb were made ischemic for 4 h and allowed to recover for 1 h (I). The nonischemic, contralateral muscles served as control (C). Measurements of Ca(2+)-ATPase properties in homogenates and SR vesicles, in mixed gastrocnemius and tibialis anterior muscles, indicated no differences between groups on maximal activity, the Hill coefficient, and Ca(50), defined as the Ca(2+) concentration needed to elicit 50% of maximal activity. In homogenates, Ca(2+) uptake was lower (P < 0.05) by 20-25%, measured at 0.5 and 1.0 microM of free Ca(2+) ([Ca(2+)](f)) in C compared with CC. In SR vesicles, Ca(2+) uptake was lower (P < 0.05) by 30-38% in I compared with CC at [Ca(2+)](f) between 0.5 and 1.5 microM. Silver nitrate induced Ca(2+) release, assessed during both the initial, early rapid (phase 1), and slower, prolonged late (phase 2) phases, in homogenates and SR vesicles, indicated a higher (P < 0.05) release only in phase 1 in SR vesicles in I compared with CC. These results indicate that the alterations in SR Ca(2+) regulation, previously observed after prolonged ischemia by our group, are reversed within 1 h of reperfusion. However, the lower Ca(2+) uptake observed in long-term, nonischemic homogenates suggests that altered regulation may occur in the absence of ischemia.
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo N2L 3G1, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Tupling
authors.forename: H
authors.initials: H
authors.lastname: Green
authors.forename: G
authors.initials: G
authors.lastname: Senisterra
authors.forename: J
authors.initials: J
authors.lastname: Lepock
authors.forename: N
authors.initials: N
authors.lastname: McKee
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D005260:Female; D006003:Glycogen / Q000378:metabolism; D006614:Hindlimb; D007511:Ischemia / Q000503:physiopathology*; D007700:Kinetics; D007773:Lactates / Q000378:metabolism; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000502:physiology*; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D015424:Reperfusion; D012519:Sarcoplasmic Reticulum / Q000502:physiology*; D013997:Time Factors
chemical_list: D007773:Lactates; D010710:Phosphates; D010725:Phosphocreatine; D006003:Glycogen; D000252:Calcium-Transporting ATPases; D003401:Creatine; D002118:Calcium