Jul 1, 1993

Effects of metabolic inhibition on cytoplasmic calcium and contraction in smooth muscle of rat portal vein

Acta Physiologica Scandinavica
K SwärdP Hellstrand

Abstract

Contractions in the rat portal vein, evoked by spontaneous action potentials or depolarizing high-K+ solution, are rapidly and reversibly inhibited by hypoxia or respiratory blockade. Intracellular free calcium ([Ca2+]i) was measured using Fura-2 to evaluate the effects of metabolic blockade on excitation-contraction coupling. Spontaneous contractions were associated with transient increases in [Ca2+]i. During exposure to cyanide (0.2-0.4 mM) or 2,4-dinitrophenol (30 microM) the duration and amplitude of the Ca2+ transients were decreased, leading to a decreased mean time integral of the individual [Ca2+]i transient, and corresponding decrease in the duration and amplitude of the contraction. Basal [Ca2+]i was increased in the presence of the metabolic inhibitors. High-K+ (40 mM) contractions caused a sustained increase in [Ca2+]i, which was not inhibited by exposure to cyanide, although the amplitude of the associated contraction was greatly reduced. Together with the earlier demonstration of decreased 20 kD myosin light chain phosphorylation under these conditions, this indicates that the activation of contraction is influenced by metabolism via the energy dependence of the light chain phosphorylation reaction. Thus at least ...Continue Reading

Mentioned in this Paper

Muscle, Smooth, Vascular
Metabolic Process, Cellular
Dinitrophenols
Calcium [EPC]
Calcium
2,4-Dinitrophenol
Entire Portal Vein
Energy Metabolism
Protoplasm
Blood Vessel

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