Lung cyclic 3',5'-adenosine monophosphate and adenylate cyclase in endotoxic shock

Cyclic 3',5'-adenosine monophosphate (cyclic AMP) and adenylate cyclase activity were measured in lungs from guinea pigs in endotoxic shock induced by an intravenous injection of Salmonella enteritidis endotoxin (10 mg/kg body weight). Both cyclic AMP content and adenylate cyclase activity were significantly elevated in lung tissue from the endotoxic guinea pigs. There was no apparent change in the affinity of adenylate cyclase for its substrate (ATP); however, the maximum velocity of the enzyme reaction was increased in lungs from the endotoxic group. Endotoxin, in the concentration range of 10(-4) to 10(-2) micrograms/ml, added to lung homogenates did not affect adenylate cyclase activity. Prostaglandins do not seem to mediate the effects of endotoxin in vivo on lung cyclic AMP since treatment of guinea pigs with indomethacin (10 mg/kg body weight) 30 min prior to endotoxin administration did not alter the endotoxin-induced increase in lung cyclic AMP.