[Effect of acute hypoxia on blood catecholamine and whole blood platelet aggregation]

Experiments were performed on 250-300 g male Sprague-Dawley rats under urethane (700 mg/kg) and alpha-chloralose (35 mg/kg) anesthesia. Plasma catecholamine concentration and the whole blood platelet aggregation were measured during normoxia, acute hypoxia, reoxygenation, acute hypoxia immediately after bilateral adrenalectomy and acute hypoxia at the end of 15 and 30 min after bilateral adrenalectomy. The plasma adrenaline concentration and the whole blood platelet aggregation increased markedly (P < 0.01), while the plasma noradrenaline concentration tended to increase (P > 0.05) during acute hypoxia. The plasma adrenaline concentration and the whole blood platelet aggregation are capable of restoring to the normal level during reoxygenation. The plasma noradrenaline concentration did not change, while the plasma adrenaline concentration and the whole blood platelet aggregation decreased significantly (P < 0.001 or 0.05) during acute hypoxia for 15 min immediately after bilateral adrenalectomy. On the other hand, plasma adrenaline and noradrenaline were not detectable during acute hypoxia 30 min after bilateral adrenalectomy while the whole blood platelet aggregation deceased markedly (P < 0.01). When adrenaline (1 ng/ml) was added to the blood (in vitro), the whole blood platelet aggregation increased significantly (P < 0.01). All the above results indicate that acute hypoxia leads to increament of whole blood platelet aggregation and plasma adrenaline concentration due to release from the adrenal gland and the increament of the whole blood platelet aggregation may be partly mediated by increased plasma adrenaline.