Similarly, in isolated lungs perfused with saline albumin solution, which usually show poor or no reactivity to hypoxia, injection of angiotensin II substantially increased reactivity to hypoxic challenges . The same effect was also seen with other excitatory substances such as noradrenaline, 4-amidopyridine, plasma or K+ . This effect of agonists on vascular reactivity may […]
In the monocrotaline experimental model of pulmonary hypertension, vascular wall damage is probably the most important causative factor. The absence of a protective effect of glucocorticoids may be one explanation for why hypoxic pulmonary hypertension was not attenuated after adrenalectomy, in spite of the described in vitro inhibition of acute hypoxic pulmonary vasoconstriction. The different […]
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 […]
Why did the effects of adrenalectomy on the effects of hypoxia differ in isolated lungs and in intact animals? It is known that rats can develop additional corticosterone secreting structures after adrenalectomy . Damasco and Coronel de Pedrazzini , however, found that 15 days after adrenalectomy, rats recovered only about a 10th of their original […]
Rats exposed to hypoxia also had increased numbers of muscularized peripheral pulmonary arteries. None of the parameters characterizing hypoxic pulmonary hypertension was influenced by adrenalectomy. Rats exposed to hypoxia had increased values of hematocrit. In chronically hypoxic sham-operated rats, hematocrit values were higher than in adrenalectomized rats exposed to hypoxia.
Effect of chronic hypoxia: At the beginning of the experiment and after exposure to hypoxia, body weight was 291.4±8.4 g and 286±8.5 g, respectively, in sham-operated rats (P<0.05, paired ttest), and 280±7.3 g and 271±9.6 g, respectively, in adrenalectomized rats (P<0.05, paired t test). Therefore, body weight was significantly less after exposure to hypoxia, and […]
It has repeatedly been shown that angiotensin II pretreatment enhances the subsequent hypoxic pressor responses in preparations perfused with artificial solutions containing no glucocorticoids . The effect is present even in the absence of significant change of baseline perfusion pressure. Therefore, pressor responses to hypoxic challenges were repeated after angiotensin II injections. Then the responses of […]