The influence of albumin and calcium on human platelet arachidonic acid metabolism.

The effects of in vitro changes in calcium and albumin on human platelet arachidonic acid metabolism were evaluated. Hypoalbuminemia enhanced the conversion of released 14C-arachidonic acid from prelabeled platelet phospholipids to the metabolites of the platelet cyclooxygenase and lipoxygenase pathways. This effect was, however, associated with a decreased release of arachidonic acid in the presence of hypoalbuminemia, such that the overall conversion of released 14C-arachidonic acid to platelet thromboxane B2 was similar in the presence of physiologic albumin concentration (3.5 g/dl) or at decreased albumin concentrations of 0.7 and 0.0 g/dl. External calcium was shown to be important for optimal platelet arachidonic acid release, with maximal release occurring at 1 mM calcium.