Platelet activating factor intravenous infusion in rats stimulates vascular lysosomal hydrolase secretion independent of blood neutrophils

Intravenous infusion of platelet activating factor into rats at doses of 5-20 nmoles/kg results in a rapid and dose-dependent increase in the plasma level of several lysosomal hydrolases, notably glucosaminidase. This hydrolase secretion occurs concomitantly with the increased vascular permeability but subsequent to the neutropenia and hypotensive responses to platelet activating factor. The glucosaminidase release in vivo does not exhibit any lasting desensitization, does not require cytochalasin B, and is quantitatively the same in rats made neutropenic with anti-neutrophil serum, and thus is different from the published in vitro degranulating effect of this lipid with neutrophils. Therefore, lysosomal hydrolase secretion may be an important pathophysiologic response to very low blood levels of platelet activating factor.