AJP - Cell Physiology, Vol 259, Issue 3 C503-C506, Copyright © 1990 by American Physiological Society
Alterations in the functional properties of skinned fibers from denervated rabbit skeletal muscle
M. M. Trachez, R. T. Sudo and G. Suarez-Kurtz
Departamento de Farmacologia Basica e Clinica, Universidade Federal do Rio de Janeiro, Brazil.
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.
