Myhaiyluk V. Sex differences of heart cholinergic regulation in condition of hypothyroidism.

Object - experimental hypothyroidism; the purpose - to establish features cholinergic regulation of heart at development of hypothyroidism; methods - elektropathologycal, morphometric, biochemical, mathematical and the results -found the peculiarities of autonomic heart regulation, sensitivity of myocardial cholinergic receptors and acetylcholine metabolism in the myocardium by development of Merkazolil hypothyroidism, depending on gender and hormones production activity of gonads. It was determined that the development of brachycardia by hypothyroidism is a result of increased activity of cholinergic effects on heart by the autonomic nervous system and reduce of adrenergic ones; this is supported by increase of cholinergic receptors sensitivity, what is more significant by females regardless of hormones production activity by the gonads. Inhibition with Mercazolil (75 mg/kg) of thyroid hormones formation causes accumulation of acetylcholine in the myocardium of atria and ventricles; this is contributed with inhibition of its enzymatic hydrolysis that is more significant for the females by surviving gonads, and by their absence for males. Lack of thyroid hormones causes accumulation of lipid peroxidation metabolits in ventricular myocardium and decrease in activity of antioxidant enzymes and inhibition of energy production causes increase of percentage of the necrotic cardiocyte and is the evidence of structural heart damage. Intensity of such changes is more significant by females regardless of gonads hormones production activity. It was found that sex hormones replacement therapy (males - testosterone, 2 mg/kg, females - hexestrol 0.1 mg/kg, progesterone 5 mg/rat) deepens signs of autonomic dysfunction in conditions of hypothyroidism, increases the role of cholinergic mechanisms in heart regulation by males mostly; under such conditions, the degree of metabolic and structural defects in the myocardium is minor than in absence of such correction, but higher than by surviving gonads.