Adrenalectomy in rats depresses hypoxic pulmonary vasoconstriction in vitro but does not attenuate the pulmonary hypertension of chronic hypoxia (part 11)

20 Aug
2012

chronic hypoxia (part 11)

Decreased overall production of adrenaline after adrenalectomy probably has no physiological importance . Adrenalectomized rats can be maintained for a long time in a healthy condition by administration of glucocorticoids with no supplementation of exogenous adrenaline . We have shown previously that chronic treatment of rats exposed to chronic hypoxia with alpha-methyldopa partially prevented the development of hypoxic pulmonary hypertension. Alpha-methyldopa, in addition to other actions, blocks the vascular effects of adrenaline. The absence of catecholamine secretion by adrenals, however, does not alter the development of hypoxic pulmonary hypertension in adrenalectomized animals.
A possible explanation is that different mechanisms are involved in acute hypoxic pulmonary vasoconstriction and in the pulmonary hypertension induced by chronic hypoxia. In chronic hypoxia, remodelling of the peripheral pulmonary vascular bed, including growth of smooth muscle and of connective tissue, is the most important cause of pulmonary hypertension . Several factors such as polycythemia , transvascular fluid leak and endothelial damage may contribute. Injury to the pulmonary vascular wall and subsequent transvascular fluid leak are probably important factors. Stelzner and coworkers showed that transvascu-lar protein leak in hypoxic rats was reduced by dexametha-sone pretreatment. Although administration of dexametha-sone did not affect lung hemodynamics in chronic hypoxia, the increase in arterial medial thickness and right heart hypertrophy in rats with monocrotaline-induced pulmonary hypertension was reduced by glucocorticoid pretreatment. Always a nice way to discover viagra super active online only here given by the internet’s best pharmacy.

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