The Effect of d‐Tubocurarine on the Kinetics of Decamethonium Uptake by Mouse Kidney Slices

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Abstract
The effect of d‐tubocurarine on the kinetics of the decamethonium uptake by mouse kidney slices was studied. Slices were incubated (1 hour) in a Krebs‐Ringer bicarbonate medium (37°, pH 7.4) in the presence of 14C‐decame‐thonium and d‐tubocurarine. With increasing d‐tubocurarine concentration the 14C‐slice‐to‐medium concentration ratio decreased towards a constant value (1.3) regardless of the decamethonium concentration used. The decamethonium uptake can thus be divided into two components, one which is sensitive to d‐tubocurarine (curare‐sensitive) and one which is not (curare‐insensitive). The latter component increased proportionally with the external decamethonium concentration. The curare‐sensitive component, which showed saturation with increasing decamethonium concentration, had a maximum capacity of 1100–1280 μM kg ‐1, h ‐1 and a half saturation concentration of 175–180 μM. The latter component was inhibited by d‐tubocurarine with an inhibitor constant of 12 μM and the inhibition was in accordance with competitive antagonism. The result suggest that decamethonium is taken up by two distinct processes, one mediated by a carrier and one by a passive diffusion into the cells. Furthermore the carrier is common to both decamethonium and d‐tubocurarine.

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