Differences in vascular response to thromboxane between intestinal mucosa and muscularis.
The effects of a thromboxane A2 (TxA2)-endoperoxide analogue, U-44069 (0.16 micrograms/min. i.a.) on blood flows to the total wall, the mucosal (= mucosa+submucosa), and muscularis (= muscularis+serosa) layers of the canine jejunum, were determined utilizing radiolabelled microspheres (diam = 13.75 microns). U-44069 significantly decreased total (-64 +/- 5%), mucosal (-67 +/- 5%), and muscularis (-53 +/- 6%) blood flows in the natural flow preparation. In the constant flow preparation, U-44069 increased jejunal vascular resistance from 2.02 +/- 0.27 to 4.6 +/- 0.65 mmHg/ml/min/100g and increased mucosal and muscularis vascular resistance by 3.5-fold and 1.5-fold, respectively. As a result, it decreased mucosal blood flow (-19 +/- 5%), but increased muscularis blood flow (+52 +/- 10%). The magnitude of U-44069-induced percent change in mucosal blood flow was significantly different from that of the muscularis. Furthermore, U-44069 significantly redistributed the total jejunal blood flow in favor of the muscularis in both natural and constant flow preparations. Intra-arterial administration of a TxA2 receptor antagonist, SQ-29548 (2.0 micrograms i.a.) reversed all of the above U-44069-induced blood flow changes to control values. Our study indicates that TxA2 produces a significantly greater vasoconstriction in the mucosa than in the muscularis of the canine jejunum. This differential action of TxA2 may have some physiological and pathophysiological significance.
Alemayehu
A
A
Department of Physiology, Michigan State University, East Lansing 48824-1101.
Chou
C C
CC
D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic; D004285:Dogs; D005231:Fatty Acids, Unsaturated; D005260:Female; D006834:Hydrazines / Q000494:pharmacology; D007261:Infusions, Intra-Arterial; D007413:Intestinal Mucosa / Q000098:blood supply / Q000187:drug effects*; D007583:Jejunum / Q000187:drug effects; D008297:Male; D008863:Microspheres; D009130:Muscle, Smooth / Q000098:blood supply / Q000187:drug effects*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors; D012039:Regional Blood Flow / Q000187:drug effects; D013928:Thromboxane A2 / Q000037:antagonists & inhibitors / Q000502:physiology*
D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D011450:Prostaglandin Endoperoxides, Synthetic; D017482:Receptors, Thromboxane; C028429:U 44069; D013928:Thromboxane A2; C045749:SQ 29548