EFFECT OF ACH AND CALMODULIN INHIBITOR ON O-2 TRANSFER FROM EXOCRINE PANCREATIC MICROVESSELS OF RATS

Effects of acetylcholine (ACh) and calmodulin (CaM) inhibitor, N-(6-am inohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7), on th e rate of O-2 release (Ro(2)) from single exocrine pancreatic microves sels of anesthetized rats were investigated with dual-spot microspectr oscopy. The surface of the pancreas was superfused with Krebs-Henselei t buffer containing various concentrations of ACh and/or W-7. Superfus ion of ACh (greater than or equal to 20 mu M) elevated Ro(2) as well a s pancreatic secretion similar to 2.5 times higher than that of contro l level, whereas superfusion of W-7 (greater than or equal to 100 mu M ) reduced similar to 50%. In both cases, O-2 inflow in single microves sels, as quantified by oxyhemoglobin inflow into the microvessels, was maintained at control level. On the other hand, superfusion of both A Ch and W-7 did not modify Ro(2) and pancreatic secretion, despite sign ificant reduction in O-2 inflow. These results indicate that 1) the AC h-induced elevation of O-2 release from single microvessels is accompl ished by increased O-2 extraction instead of increased O-2 inflow in t he microvessels, and 2) the activity of a W-7-sensitive Ca2+ binding p rotein, most likely CaM, is responsible for half of the microvascular O-2 transfer and of the pancreatic exocrine secretion.