Species variability in the cardiovascular and hematologic effects of zymosan-activated plasma infusion

Abstract

The anaphylatoxins have been implicated in the pathogenesis of endotoxin shock and the adult respiratory distress syndrome. Both endotoxin and zymosan activate the complement pathway. Because there are marked species differences in the cardiovascular and hematologic effects of endotoxin infusion, the purpose of this study was to compare the effects of zymosan-activated plasma (ZAP) infusion in dogs, sheep, and baboons. ZAP was infused (0.11 ml/kg/min for 60 min) into dogs ( n = 5), baboons ( n = 5), and sheep ( n = 3). The infusion of ZAP resulted in significant changes in heart rate (HR) ( P < 0.03), mean arterial pressure (MAP) ( P < 0.002), pulmonary artery pressure (PAP) ( P < 0.004), cardiac index (CI) ( P < 0.034), and extra vascular lung water (EVLW) ( P < 0.001). A specific difference between the species' response to ZAP infusion was present when evaluating the effect of ZAP on MAP ( P < 0.02), HR ( P < 0.003). EVLW ( P < 0.001), platelet count ( P < 0.01), and white blood cell count ( P < 0.01). The main species differences in the changes in MAP, HR, and platelet count were an increase in MAP, decrease in HR, and decrease in platelet count that occurred in dogs. The species difference in the WBC count was the result of ZAP-induced neutropenia in sheep versus a leukocytosis in dogs. Unlike dogs and baboons, sheep developed an increase in EVLW. Like endotoxin, the cardiovascular and hematologic effects of ZAP infusion are species dependent. Of the three species studied, dogs were distinctly different. Except for the changes in EVLW sheep and baboons responded in a qualitatively similar fashion, although the magnitude of the sheep's responses was always greater.