The determinants of the altered glucoregulation in acidosis were investigated in anesthetized dogs. Because CO2 rapidly equilibrates and its effects are mediated by pH changes, CO2 inhalation was examined. Plasma acid-base composition, glucose, insulin, glucagon, and blood flows were evaluated before and after an intravenous glucose load (1.2 +/- 0.1 g/kg body wt) in normal and acidotic dogs with flow probes and catheters chronically implanted in the portal circulation. A simultaneous infusion of phentolamine (5 micrograms.kg-1.min-1), propranolol (3.5 micrograms.kg-1.min-1), both, or none was used. All acidemic dogs had lower hepatic extraction of insulin and greater hyperglycemia after the glucose challenge; thus the adrenergic system is not critical for these responses. Because arterial insulin levels were either normal (propranolol) or increased (all others) in acidosis, insulin resistance was likely. Insulin infusion (2 and 4 mU.kg-1.min-1) with euglycemic clamp and [3-3H]glucose documented that acidemia decreases peripheral glucose utilization and the insulin suppression of hepatic glucose production. Acidemia also enhances plasma glucagon levels, yet this effect plays a limited role in the observed hyperglycemia.