PARADOXICAL CHANGES IN ORGAN BLOOD-FLOW AFTER ARGINASE INFUSION IN THE NONSTRESSED RAT

Arginine (ARG) is the precursor of nitric oxide (NO), a potent vasodil ator. Arginase (ASE) is released following hepatocellular damage, resu lting in low plasma ARG levels. The effect of ASE infusion on hemodyna mics was studied. Rats received a 20 min ASE or saline infusion, and s ystemic hemodynamics and organ blood flow were studied, at 30 and 270 min, using radiolabeled microspheres. Compared with control, ASE resul ted (30 min) in 1) undetectable ARG levels; 2) higher mean arterial pr essure and total peripheral resistance (both p < .05); 3) higher blood flow to the heart, kidneys, stomach, small intestine tall p < .05), a nd spleen (p < .001); and 4) lower vascular resistance in the heart, k idneys, stomach, and small intestine tall p < .05) and in the spleen ( p < .005), At 270 min, ASE rats had similar organ blood flow and highe r nitrate levels in urine and plasma (both p < .05) compared with cont rol. We conclude that ASE reduces ARG levels with simultaneous increas e in mean arterial pressure and total peripheral resistance. Higher ni trate production, suggesting higher NO formation in the presence of lo w ARG plasma levels, is paradoxical but could explain the higher blood flow in some organs, The increased total peripheral resistance during higher nitrate formation suggests regional differences in dependency of NO production on plasma ARG levels.