Myocardial responses to isoproterenol are altered by chronic alcoholism and infection

Alcohol, consumed as 36% of the caloric intake for 8-10 wk, causes a potentiation of cardiac dysfunction induced by a second insult, sepsis. Because chronic alcoholism may attenuate the responsiveness of the myocardium to catecholamine stimulation, and because catecholamine support seems to be essential for the myocardium to generate an adequate cardiac output in sepsis, we hypothesized that the heart from the alcoholic septic rat would show a compromised inotropic responsiveness to catecholamines compared with the heart from the nonalcoholic septic rat. To test this hypothesis, rats were fed an ethanol-containing or control liquid diet for 8-10 wk and were then made septic with live Escherichia coli (10(10) E. coli) through a dorsal subcutaneous catheter. The next day, hearts were removed and perfused at a constant hydrostatic pressure, and a compliant balloon was placed in the left ventricule for measurement of pressure (LVP). Hearts were paced at 350-360 beats/min. Hearts were allowed to stabilize for 15 min, and then the response to a submaximal dose of isoproterenol (Iso) was measured. Hearts recovered for 30 min, at which time the response to a maximum dose of Iso was recorded. Basal (pre-Iso) LVP was lower in the control septic and alcoholic septic groups than in the control and alcohol groups. However, the maximum increase in LVP in response to Iso was greater in the two septic groups than in the two nonseptic groups. The peak LVP in response to Iso was similar in the control, septic, and alcoholic septic groups, and was significantly greater than in the alcohol group.(ABSTRACT TRUNCATED AT 250 WORDS)