PORCINE DIAPHRAGMATIC ARTERIES - AN INVITRO COMPARATIVE-STUDY

The purpose of the experiment was to determine whether diaphragmatic c irculation could be compared to other skeletal muscle circulation or w hether it has an originality of its own. Diaphragmatic (phrenic and co stophrenic arcade arteries), coronary, femoral and cerebral arteries w ere taken up from anaesthetized pigs, cut into rings and suspended in organ chambers for isometric tension recording. Vasopressin induced a maximal contraction of the femoral artery, no significant changes in t one in cerebral and coronary arteries, and only minimal contraction (3 0% of the maximum) in diaphragmatic arteries. These results were obtai ned in a state of basal level of tension or in vessels contracted with prostaglandin F2alpha. The endothelium did not influence the response in any of the vessels investigated. Norepinephrine induced a contract ion in the femoral artery and a relaxation in the coronary artery whic h was not influenced by the endothelium. Isoproterenol could relax the coronary but not the femoral or the diaphragmatic arteries. The alpha 2-adrenoceptor agonist UK 14304 induced endothelium-dependent relaxati on in the diaphragmatic and coronary arteries, but not in the femoral arteries. Phenoxybenzamine unmasked a small alpha-adrenoceptor reserve in the diaphragmatic arteries. These results suggest that diaphragmat ic circulation has protective mechanisms in order to preserve a correc t supply to the vital respiratory muscle it subserves.