[Disorders of thrombocyte function and/or endothelial cell damage as a cause of primary pulmonary hypertension?]

The pathophysiology of pulmonary hypertension is, in many cases, unclear and this is true especially for patients with dietary pulmonary hypertension. This paper discusses the hypothesis that platelets, directly or through their interaction with the pulmonary endothelial cell, are involved in the development of pulmonary hypertension. Platelets release vasoactive substances during aggregation or activation and these substances lead to pulmonary vasoconstriction and pulmonary hypertension. The primary target of the activated platelets could be the endothelial cell which has also been demonstrated in animal experiments with crotalaria-induced pulmonary hypertension. Changes in thromboxane--platelets and prostacyclin--endothelial cell interactions could be the basic mechanism responsible for endothelial proliferation and pulmonary vasoconstriction. It has not been ascertained, however, whether the activation of platelets or endothelial dysfunction is the primary lesion. In various animal experiments, changes in platelet function and endothelial damage, as well, have been shown to be initiated by exogenous influences. The investigation of platelets or endothelial cell function in patients with pulmonary hypertension showed evidence of platelet activation but not platelet hyperreactivity. An impaired fibrinolytic activity, which was found in the majority of these patients, was regarded as indicative of endothelial dysfunction. An interference in the physiological interaction of circulating platelets and endothelial cells in the lung with resulting endothelial proliferation and vessel occlusion could well be the initial factor. This process would be self-perpetuating in the development of pulmonary hypertension. An additional example of dietary-induced pulmonary hypertension was observed in patients in Spain after the ingestion of toxic oil.(ABSTRACT TRUNCATED AT 250 WORDS)