Kinetics and inotropic action of probenecid in guinea-pig heart in vitro

Probenecid (100-750 microgram . ml-1) was found to inhibit cardiac contraction force in untreated and digoxin-treated (100 microgram . ml-1) isolated right guinea-pig atrium in vitro by a reversible process, without influencing beating frequency. At low concentrations (1.5--60 microgram . ml-1), 14C-probenecid was accumulated into right atrium by an oxygen-dependent process. Correlation between uptake and negative inotropic action of probenecid could not be found.