Spontaneous electrical and mechanical activity of isolated rat portal vein was abolished by cooling to 10°C as indicated by sucrose gap recordings. Graded increases in [K+]o at this temperature caused only transient propagated activity after which the muscle stabilized at constant membrane potentials and contracture tensions. Complete relaxation occurred on return to normal [K+]o. An S-shaped relation was found between log [K+]₀ and contracture force; the mechanical threshold corresponded to about 9 mM K+ and the maximal response was reached at 40-50 mM. Variations in [Ca2+]o from 0.4 to 12.5 mM did not appreciably affect the relative concentration-effect curve for K+. Thus a graded relation between depolarization and contractile force has been demonstrated in this normally spike-generating smooth muscle.

Keywords:
Rat portal vein, Cooling, Potassium contracture, Calcium
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© 1974 S. Karger AG, Basel
1974
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