Inotropic effects of ethanol on the isolated papillary muscle of the diabetic rat.
The present study was designed to characterize the inotropic effects of ethanol (ETOH) on diabetic rat heart. Left-ventricular papillary muscles, from normal and diabetic (streptozotocin, 50 mg/kg IV; 6 weeks) rats, were superfused with Tyrode's solution at 30 oC while driven at 0.5 Hz. Developed tension, time-to-peak tension (TPT), time-to-90% relaxation (RT90), maximum rate of tension developed (+VT) and maximum rate of tension fall (-VT) were determined in the absence and presence of clinically relevant concentrations of ETOH (80-240 mg/dl, i.e., 1.7-5.2 mM). Ethanol decreased developed tension, TPT, RT90, and VT in papillary muscles from both groups. Ethanol 80 mg/dl reduced tension, +VT and -VT in preparations from diabetic animals. However, this concentration had no effect on normal muscles. An intermediate concentration of ETOH (120 mg/dl), decreased tension and +VT in preparations from both groups, whereas a higher dose (240 mg/dl) decreased tension, TPT, RT90, VT, and -VT, and induced spontaneous contractures in both groups. The negative inotropic effects of ethanol were generally concentration-dependent and the diabetic myocardium maybe more sensitive to inotropic effects of clinically relevant concentrations of ETOH. Ethanol-induced diminution in contractile tension in normal and diabetic myocardium is associated with reduced contraction and relaxation velocity as well as their respective duration.
Department of Physiology, Wayne State University, School of Medicine, Detroit, MI 48201.
R A
RA
Brown
E
E
Robinson
J C
JC
Dunbar
D000818:Animals; D003864:Depression, Chemical; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D000431:Ethanol