AJP - Heart and Circulatory Physiology, Vol 271, Issue 1 1-H7, Copyright © 1996 by American Physiological Society
Effect of ACh and calmodulin inhibitor on O2 transfer from exocrine pancreatic microvessels of rats
A. Seiyama, H. Kosaka and T. Shiga
Department of Physiology, Osaka University, Medical School, Japan.
Effects of acetylcholine (ACh) and calmodulin (CaM) inhibitor,
N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7), on
the rate of O2 release (Ro2) from single exocrine pancreatic microvessels
of anesthetized rats were investigated with dual-spot microspectroscopy.
The surface of the pancreas was superfused with Krebs-Henseleit buffer
containing various concentrations of ACh and/or W-7. Superfusion of ACh
(> or = 20 microM) elevated Ro2 as well as pancreatic secretion
approximately 2.5 times higher than that of control level, whereas
superfusion of W-7 (> or = 100 microM) reduced approximately 50%. In
both cases, O2 inflow in single microvessels, as quantified by
oxyhemoglobin inflow into the microvessels, was maintained at control
level. On the other hand, superfusion of both ACh and W-7 did not modify
Ro2 and pancreatic secretion, despite significant reduction in O2 inflow.
These results indicate that 1) the ACh-induced elevation of O2 release from
single microvessels is accomplished by increased O2 extraction instead of
increased O2 inflow in the microvessels, and 2) the activity of a
W-7-sensitive Ca2+ binding protein, most likely CaM, is responsible for
half of the microvascular O2 transfer and of the pancreatic exocrine
secretion.
