Effect of procaine on potassium permeability of canine tracheal smooth muscle.
Procaine depolarized the cell membrane, and initiated oscillations and spike-like potentials in canine tracheal smooth muscle, at concentrations between 1 and 5 mM, while higher concentrations of this drug suppressed the spontaneous activities. Inhibitory effects of procaine on 86Rb-efflux were not evident in normal solution. In high K solution, procaine decreased the rate of 86Rb-efflux, in a dose dependent manner, and a Scatchard plot suggested two sites of action for procaine. The site with a higher affinity (KD = 0.26 mM) may directly regulate the K permeability and interact with procaine in a one to one manner. In high concentrations (greater than or equal to 10 mM), procaine interacted at another site and the tracheal smooth muscle which contracted in high K solution relaxed almost completely. Thus, the decrease in 86Rb-efflux by high concentrations of procaine may partly result from a decrease in intracellular Ca concentration. It is proposed that procaine has the dual effect by inhibiting the K conductance: (1) depolarization of cell membrane, (2) increase in membrane excitability. These actions would explain the spontaneous electrical activity induced by procaine in canine tracheal smooth muscle.
D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D010539:Permeability; D011188:Potassium / Q000378:metabolism*; D011343:Procaine / Q000494:pharmacology*; D012413:Rubidium / Q000378:metabolism; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism
D013757:Tetraethylammonium Compounds; D011343:Procaine; D012413:Rubidium; D011188:Potassium