In vivo measurement of nitric oxide production in porcine gut, liver and muscle during hyperdynamic endotoxaemia

1 During prolonged endotoxaemia, an increase in arginine catabolism may result in limiting substrate availability for nitric oxide (NO) production. These effects were quantitated in a chronically instrumented porcine endotoxaemia model. 2 Ten days prior to the beginning of the experiments, pigs were catheterized. On day 0, pigs received a continuous infusion of endotoxin (3 mug kg(-1) h(-1)) over 24 It and were saline resuscitated. Blood was drawn from the catheters at 0 and 24 It during primed-infusion of N-15(2)-arginine and P-aminohippurate to assess N-15(2)-arginine to N-15-citrulline conversion and plasma flow rates, respectively, across the portal-drained viscera, liver and hindquarter. 3 During endotoxin infusion a hyperdynamic circulation with elevated heart rate, cardiac index and decreased mean arterial pressure was achieved, characteristic of the human septic condition. 4 Endotoxin induced NO production by the portal-drained viscera and the liver. The increased NO production was quantitatively matched by an increase in arginine disposal. Nitrite/nitrate levels remained unchanged during endotoxaemia. 5 Despite an increased arginine production from the hindquarter and an increased whole-body arginine appearance rate during endotoxin infusion, the plasma arginine concentration was lower in endotoxin-treated animals than in controls. On a whole-body level, the muscle was found to serve as a major arginine supplier and, considering the lowered arginine plasma levels, seems critical in providing arginine as precursor for NO synthesis in the splanchnic region.