FACTORS ASSOCIATED WITH HYPERDYNAMIC OR HYPODYNAMIC CIRCULATION AND ROLE OF PLATELET-ACTIVATING-FACTOR IN HEMODYNAMIC-ALTERATIONS IN BACTERIAL PERITONITIS IN CONSCIOUS RATS

Male Wistar rats injected intraperitoneally (i.p.) with 10(9) U Escher ichia coli ATCC 25922 developed acute bacterial peritonitis. Hemodynam ic studies, with microspheres labeled with Ru-103 Co-57, and Sn-113, w ere performed before, 30 min after bacterial injection, and 30 min aft er administration of either the platelet-activating factor (PAF) antag onist BN-52021 (5 mg/kg body weight) or isotonic saline, A blood sampl e of 0.3 mi was obtained for bacterial culture and endotoxemia measure ments. Plasma PAF levels were measured in a different group of 10 cont rol rats and 20 animals with experimental peritonitis. One group of ra ts injected with E, coli (n = 13) displayed hyperdynamic circulation, with an increase in cardiac output (GO) from 15.1 +/- 1.2 to 19.4 +/- 1.1 ml/min/100 g body weight and a decrease in total peripheral resist ance (TPR) from 19.5 +/- 2.4 to 14.9 +/- 1.1 dynes . s . cm(-5) 10(-4) . Furthermore, these rats showed high endotoxin blood concentrations a nd low hemoculture levels, The remaining 7 peritonitic rats showed a s ignificant decrease in CO from 16.3 +/- 1.6 to 12.7 +/- 1.2 ml/min/100 g body weight and an increase in TPR from 17.3 +/- 1.8 to 22.6 +/- 2. 8 dynes . s . cm(-5) 10(-4). In addition, these rats showed low endoto xin blood concentrations and high hemoculture levels. Endotoxin blood concentrations were positively correlated with the change in CO (r = 0 .87, p < 0.05), and cell hemocultures were positively correlated with CO (r = 0.89, p < 0.05). Rats with high endotoxin blood levels showed higher PAF plasma levels than control rats or peritonitic rats with lo w endotoxin blood levels. When peritonitic rats were injected with the specific PAF-receptor blocker BN-52021 (5 mg/kg body weight) as a bol us, CO and TPR returned to baseline values in both groups of animals. These data suggest that the hemodynamic changes induced by bacterial p eritonitis depend on endotoxemia and bacteremia in opposite ways. In a ddition, PAF appears to be involved in both the hyperdynamic and hypod ynamic hemodynamic changes shown by peritonitic rats.