To establish potential anti-ischemic effects of
testosterone and
estradiol on myocardium we used isolated rat hearts in accordance with Langendorff, exposed to 40 min of
ischemia and reperfusion. Rats were pretreated for 10 days, males with
testosterone and females with
estradiol and
injuries from those hearts were compared to the hearts where both drugs were applied to the isolated hearts directly. The myocardial
injuries were determined by changes in coronary flow, incidence and duration of arrhythmias and
lactate dehydrogenase release rates used as markers for level of cardiac injury during reperfusion. Coronary flow in the hearts of animals pretreated with
estradiol during reperfusion increased by 68.7+/-3.6% (P<0.001) and in those pretreated with
testosterone by 50.1+/-2.1% (P<0.05) vs. control hearts.
Lactate dehydrogenase release rates decreased in the hearts of animals pretreated with
estradiol by 55.7+/-1.9% (P<0.01) vs. controls and by 58.8+/-3.0 (P<0.01) vs. directly applied
estradiol. Duration of
ventricular fibrillation decreased after 10 days application of drugs, from 9.42+/-0.81 min to 4.58+/-0.93 min (P<0.05) with
estradiol and from 9.19+/-1.05 min to 4.65+/-0.51 min (P<0.05) with
testosterone. The duration of
heart arrest decreased in 10 days application of
testosterone from 2.42+/-0.16 min to 20.0+/-12.26 s (P<0.01). Hearts from animals pretreated for 10 days with
estradiol showed more cardioprotective effects during reperfusion than those pretreated with
testosterone.
Testosterone pretreatment, despite being less effective in cardioprotection than
estradiol, improved coronary flow and decreased arrhythmias as effectively as
estradiol.