[Contractile function of the heart in rats after chronic stress and thyroidin treatment]

We examined heart tolerance of rats, that had been exposed to two-month social stress, to acute overload caused by aortic coarctation and investigated physiological doses of thyroid hormones used to treat stress-induced tolerance changes. Cardiac contractility of rats adapted to chronic stress and exposed to overload was similar to that of controls and the functional maximum reached at the 5th second of aortic coarctation was 33-53% higher than that in the controls. However, tolerance of chronically adapted hearts measured by their ability to maintain increased contractility during 25 s aortic coarctation was 1.4-1.8 times lower. Thyroid hormones in physiological doses normalized tolerance of chronically stressed hearts to overload induced by aortic coarctation.