Alterations in the functional properties of skinned fibers from denervated rabbit skeletal muscle.
Isometric tension was recorded in vitro from chemically skinned fibers obtained from normal and 14-day-denervated extensor digitorum longus muscles of the rabbit. Denervation potentiated the tensions elicited by pCa 6.0 but did not modify the pCa value (5.6) required for maximum tension. Ca2+ transport across the membranes of the sarcoplasmic reticulum (SR) was markedly affected by denervation. Thus the rate of ATP-dependent net Ca2+ uptake increased significantly, and the spontaneous release ("leakage") of the Ca2+ stored in the SR was significantly reduced in denervated fibers. These effects lead to increased accumulation of Ca2+ in the lumen of the SR. The dose-response curve for the halothane-induced contractures of Ca2(+)-loaded skinned fibers was displaced to the left after denervation. Thus 0.7 mM halothane, a concentration that elicited no tension in 10 control fibers, induced contractures in the 10 denervated fibers tested. The potentiation of the halothane-induced tensions is attributed mainly to the larger stores of Ca2+ in the SR of denervated fibers. The possibility that denervation may also affect the interaction of halothane with the SR membranes is discussed.
Departamento de Farmacologia Básica e Clínica, Universidade Federal do Rio de Janeiro, Brazil.
M M
MM
Trachez
R T
RT
Sudo
G
G
Suarez-Kurtz
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D006221:Halothane / Q000494:pharmacology; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009121:Muscle Denervation; D009132:Muscles / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism
D002110:Caffeine; D000255:Adenosine Triphosphate; D002118:Calcium; D006221:Halothane