Effects of dopamine on endotoxin and hemorrhagic shock in the canine stomach

Studies were conducted to evaluate the effects of dopamine on gastric electrophysiopathology in endotoxin and hemorrhagic shock. Intraarterial infusion of dopamine (15.5 or 31 microgram/kg/min) in the in vivo stomach preparation produced an immediate decrease in electrical potential difference (PD), which then returned and exceeded control values. No changes in resistance (R) and blood pressure were observed. These electrophysiological responses of the gastric mucosa to dopamine are very similar to the actions of epinephrine. The in vitro studies demonstrated that active transport of Na+ was stimulated with an addition of dopamine or epinephrine (2 X 10(-4) M) to the serosal solutions of the isolated gastric mucosa. In addition, the in vivo studies demonstrated that both 40% hemorrhage and 1 mg/kg of endotoxin given as an intravenous bolus decreased PD and blood pressure and increased R although dopamine was continuously infused intraarterially for 60 minutes prior to and following hemorrhage or endotoxin. Administration of endotoxin at the onset of dopamine infusion decreased both blood pressure and PD initially. While PD showed a complete recovery at a later stage, blood pressure never returned to control levels. These results, combined with previous observations, suggest that: 1) dopamine has no beneficial action on the gastric mucosa during hemorrhagic or endotoxin shock; 2) dopamine acts on the electrophysiology in vivo and Na+ fluxes in vitro in the gastric mucosa in a manner similar to epinephrine; and 3) decrease in blood flow may be responsible for the observed decrease in transmural PD after dopamine and epinephrine in vivo.