Influence of insulin treatment on the mechanical properties and inotropic response to ethanol in diabetic myocardium
Brown, R.A.; Adams, A.; Savage, A.O.
Journal of the Association for Academic Minority Physicians the Official Publication of the Association for Academic Minority Physicians 7(1): 25-30
1996
ISSN/ISBN: 1048-9886 PMID: 8820240 Document Number: 463398
Diabetes significantly affects cardiac performance, as does ethanol. To assess whether insulin treatment alters the inotropic response to acute ethanol exposure and reverses diabetes-induced myocardial dysfunction, male Wistar rats were made diabetic using streptozocin, 55 mg/kg intravenously. The inotropic effect of ethanol on normal, diabetic, and insulin-treated (8 weeks) diabetic animals was studied using isolated, left-ventricular papillary muscle preparations superfused with Tyrode's solution under isometric conditions. Peak tension developed, time to peak tension (TPT), time to 90% relaxation (RT90), maximum rate of tension developed (+VT), and maximum rate of fall in tension (-VT) were determined in the absence and presence of clinically relevant concentrations of ethanol for 10 minutes. In insulin-treated diabetic muscles, baseline developed tension, +VT, and -VT were enhanced, and the prolongation of TPT and RT90, characteristic of diabetic myocardium, was attenuated. The magnitude of the reduction in developed tension in response to ethanol, 80 mg/dL, was slightly greater in untreated diabetic myocardium. Higher concentrations of ethanol (120 to 240 mg/dL) decreased tension in all groups and was of similar magnitude. The negative inotropic effect of higher ethanol concentrations was associated with shortening of TPT and RT90, as well as a diminution of +VT and -VT. It is concluded that with insulin treatment, the mechanical properties of diabetic myocardium are normalized; however, neither the myocardium's sensitivity to ethanol nor the overall magnitude of ethanol's negative inotropic effect is modified by insulin treatment.