Pulmonary hypertensive response to endotoxin in cellulose-primed and unprimed broiler chickens

Previous studies indicate that individual broilers vary widely in their pulmonary vascular responsiveness to i.v. injections of endotoxin. This individual variability may reflect differences acquired during previous respiratory challenges or genetic variability that may be associated with susceptibility to pulmonary hypertension syndrome (ascites). In the present study, we compared the endotoxin responses of 4- to 5- wk-old control broilers (unprimed) and broilers in which the pulmonary vasculature had been immunologically challenged 48 h previously by an i.v. injection of cellulose micro-particles (primed). The injected cellulose micro-particles are carried in the venous blood to the lungs, where they become trapped in the pulmonary vasculature and initiate acute focal inflammatory responses within the surrounding lung parenchyma. Physiological variables (respiratory rate, heart rate, pulmonary and systemic arterial pressures) were evaluated prior to and following the i.v. administration of 1 mg of Salmonella typhimurium endotoxin. Prior to endotoxin injection, the respiratory rate was higher in primed than in unprimed broilers; however, the heart rate, pulmonary arterial pressure, and systemic arterial pressure did not differ between groups. Broilers in both groups exhibited similar ranges of individual variability in their endotoxin responses. The overall time of onset, magnitude, and duration of the pulmonary hypertensive responses were similar for both groups. Accordingly, the initiation of a preexisting inflammatory response within the lung parenchyma did not alter the timing, amplitude, or variability of the subsequent pulmonary hypertensive response to endotoxin in broilers.