Role of the endothelium in regulation of contractile and dilatatory reactions of the aorta in rats with experimental hypothyrosis

The role of endothelium in regulation of the functional activity of vessels in experimental hypothyrosis was studied during different periods of ontogenesis. The study was carried out on isolated segments of the aorta from young (1 month) and adult (4-5 months) female rats. Hypothyrosis was induced by addition of thyrostatic mercasolil to the ration. Vascular stenosis was induced by norepinephrine, dilatation by carbacholine. The specific features in the mechanisms regulating arterial tone of euthyroid rats in the early ontogenesis are explained by a lower basal level of NO and specificity and/or density of adrenergic and cholinergic receptors, characteristic of this age. Reactions of arteries to norepinephrine and carbacholine in hypothyrosis are largely determined by age, modification of adrenergic receptor system of smooth-muscle cells, and endothelial function. A lower level of basal NO synthesis, characteristic of young hypothyroid animals, can be regarded as one of the main determinants of vasoconstrictive effect stimulation in hypothyrosis.