APStracts 3:0396H, 1996.

Cardiovascular reflex responses to ischemia during occlusion of the celiac and/or superior mesenteric arteries. Rendig, Stephen V., Premjit S. Chahal, and John C. Longhurst. Division of Cardiovascular Medicine, Departments of Internal Medicine and Human Physiology, University of California, Davis, California 95616, Division of Cardiovascular Medicine, University of California Davis, TB 172, Davis, CA 95616, Tel: (916) 752-0717, FAX: (916) 752-3264

APStracts 3:0396H, 1996.

Global ischemia of the abdominal visceral region leads to profound reflex cardiovascular responses. However, the separate contributions of the celiac and superior mesenteric artery (SMA) vascular beds to the visceral ischemia-induced cardiovascular reflex have not been investigated. Accordingly, we compared the effects of single and combined occlusions of the celiac and SMA on mean arterial blood pressure in anesthetized cats. Tissue mass, tissue pH of selected organs, as well as blood gases, pH and lactate of regional venous blood from representative ischemic organs were measured to compare the magnitude of the ischemic insults. The blood pressure increment produced by ligation of the SMA (30 +/- 4 mmHg) was significantly (P&LT;0.05) larger than that produced by occlusion of the celiac artery (18 +/- 4 mmHg). Combined occlusion of the two vessels augmented blood pressure by 53 +/- 12 mmHg, a significantly greater increase than that induced by ligation of the celiac artery alone. Venous lactate levels increased in both vascular beds during ischemia but attained statistical significance only during occlusion of the SMA. The decline in blood pH was significantly greater in venous blood from the superior mesenteric vascular bed than in splenic venous blood (-0.20 +/- 0.03 pH units vs. -0.08 +/- 0.02 pH units, P&LT;0.05, respectively). In addition, the decline in tissue pH during SMA occlusion was significantly greater in selected organs perfused by this vascular bed (i.e., colon, jejunum) than in selected organs perfused by the celiac artery (i.e., liver, pancreas and proximal duodenum) during celiac occlusion. Conversely, the tissue mass subserved by the celiac artery was significantly (P&LT;0.05) greater than that perfused by the SMA (182 +/- 27g vs. 131 +/- 17g, respectively). These data suggest that the larger cardiovascular reflex associated with ischemia of regions subserved by the SMA compared to regions served by the celiac artery may be related to a greater increase of hydrogen ion and lactic acid concentration in tissue supplied by the SMA bed. In addition, the large reflex increase in blood pressure produced by combined occlusion of the celiac and SMA likely is an additive effect of occlusion of both vessels, presumably related to the larger organ mass and the recruitment of more sensory nerve fibers.

Received 29 April 1996; accepted in final form 3 September 1996.
APS Manuscript Number H379-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996