The effect of harmaline on unidirectional potassium fluxes and ouabain binding in renal cell cultures.

Harmaline inhibits K+ influx into primary cell cultures of ground squirrel kidneys to a greater extent than either ouabain or furosemide. A concentration of 200 microM harmaline was required to inhibit half of the total K+ influx; this effect was also seen at low temperature (5 degrees C), and in another species (hamster). Although kinetic analysis of K+ influx indicates that harmaline does not compete with extracellular K+, harmaline did reduce the binding of [3H]ouabain to the cells. K+ efflux was also reduced. Therefore, harmaline may inhibit the furosemide-sensitive Na+/K+ cotransport system as well as the ouabain-sensitive Na+/K+ pump.