Hypoxic Pulmonary Hypertension: Changes in Platelet Size and Number

Abstract

Circulating platelets have been implicated in the hypoxic pulmonary pressor response. This study was undertaken to assess the effects of acute hypoxia-induced pulmonary hypertension on platelet volume and number across the pulmonary circulation in anesthetized newborn lambs. Seven animals were instrumented for measurement of pulmonary vascular resistance. All measurements were made during normoxia and after 5 and 30 minutes of hypoxia (10 to 12% oxygen breathing). Hypoxia caused a doubling of the pulmonary vascular resistance. During hypoxic vasoconstriction, platelet volume decreased rapidly while traversing the lung but was not affected on return to the lung after traversing the systemic circulation. Platelet numbers were unchanged on leaving the lung but were decreased on entering the lung during hypoxia. Our data are consistent with the release of platelet contents in the lung during hypoxic pulmonary hypertension.

Angiogenesis-related gene expression profiling in ventilated preterm human lungs

“…It remains to be determined whether platelet expression of thrombospondin-1 in preterm lungs is regulated by any of the candidate factors implicated in the pathogenesis of BPD, such as infection/inflammation, oxygen toxicity, hyperoxia/hypoxia, and mechanical stretch/strain [1]. Several lines of evidence suggest that megakaryocyte and/or platelet homeostasis and activation may be modulated by oxygen tension, hypoxia and/or hyperoxia, at least in some conditions [58][59][60][61]. Interestingly, a recent report described up-regulation of thrombospondin-1 mRNA expression in ovine fetal lungs subjected to stretch following tracheal occlusion [52].…”

Role of serotonin in the pathogenesis of acute and chronic pulmonary hypertension

“…144 Patients with chronic obstructive pulmonary disease (COPD) and pulmonary hypertension show evidence of greater activation of platelets in pulmonary vessels than those with normotensive COPD,145 146 and a reduced platelet survival time is also found 147. In animal models platelets release their contents into the lung during hypoxic vasoconstriction 148. The release of platelet contents and the progression of pulmonary hypertension in patients with COPD may be slowed with the use of the platelet-inhibiting drug dipyridamole 149…”