Triiodothyronine concomitantly inhibits calcium overload and postischemic myocardial stunning in diabetic rats.
Acute effects of triiodothyronine (T3) on postischemic myocardial stunning and intracellular Ca2+ contents were studied in the isolated working hearts of streptozotocin-induced diabetic rats and age-matched controls. After two weeks of diabetes, serum T3 and T4 levels were decreased to 62.5% and 33.9% of control values. Basal preischemic cardiac performance did not differ between diabetic and control rats. In contrast, during reperfusion after 20-min ischemia, diabetic rats exhibited an impaired recovery of heart rate (at 30-min reperfusion 57.5% of baseline vs. control 88.5%), left ventricular (LV) systolic pressure (44.1% vs. 89.5%), and cardiac work (23.1% vs. 66.0%). When 1 and 100 nM T3 was added before ischemia, heart rate was recovered to 77.2% and 81.8% of baseline, LV systolic pressure to 68.3% and 81.9%, and cardiac work to 50.8% and 59.0%, respectively. Diabetic rat hearts showed a higher Ca2+ content in the basal state and a further increase after reperfusion (4.96+/-1.17 vs. control 3.78+/-0.48 micromol/g, p<0.01). In diabetic hearts, H+ release was decreased after reperfusion (5.24+/-2.21 vs. 8.70+/-1.41 mmol/min/g, p<0.05). T3 administration caused a decrease in the postischemic Ca2+ accumulation (lnM T3 4.66+/-0.41 and 100 nM T3 3.58+/-0.36) and recovered the H+ release (lnM T3 16.2+/-3.9 and 100 nM T3 11.6+/-0.9). T3 did not alter myocardial O2 consumption. Results suggest that diabetic rat hearts are vulnerable to postischemic stunning, and T3 protects the myocardial stunning possibly via inhibiting Ca2+ overload.
Oshiro
Y
Y
Second Department of Internal Medicine, Faculty of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan.
Shimabukuro
M
M
Takasu
N
N
Asahi
T
T
Komiya
I
I
Yoshida
H
H
D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects* / Q000503:physiopathology; D006439:Hemodynamics / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D017682:Myocardial Stunning / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D010477:Perfusion; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013311:Streptozocin; D013974:Thyroxine / Q000097:blood / Q000502:physiology; D014284:Triiodothyronine / Q000494:pharmacology*; D016277:Ventricular Function, Left / Q000187:drug effects
D014284:Triiodothyronine; D013311:Streptozocin; D013974:Thyroxine; D002118:Calcium