Effect of pH alterations on the vascular reactivity of dog isolated perfused mesenteric arteries.

Accepted January 23, 1984 It is well recognized that the pH of the perfusing fluid is one of the important factors involved in the control of vascular reactivity. Respiratory acidosis diminishes the effect of vasoconstrictor substances on blood vessels (1). Rogers et al. (2) demonstrated that increasing pH potentiated the increase in perfusion pressure to administered catechol amines in isolated perfused mesenteric arteries. Recently, a new model of an isolated arterial preparation was developed by Hongo and Chiba (3) and modified by Tsuji and Chiba (4). By using this method, we have attempted to evaluate responses of dog isolated mesenteric arteries to several vasoconstrictor substances at low, normal and high pH levels of perfusing fliud. Twelve mongrel dogs weighing 9-16 kg were anesthetized with sodium pentobarbital (30 mg/kg, i.v.) and sacrificed by rapid exanguination, after treatment with sodium heparin (500 units/kg, i.v.). The mesenteric artery was dissected and carefully removed. Isolated mesenteric arteries selected for study were 10-15 mm in length and 0.5 1.0 mm in outer diameter, and they were cannulated as described previously (3, 4). Briefly, a steel cannula (21-27 gauge, 0.40-0.83 mm in outer diameter and 3 cm in length) was prepared with one end sealed. Near the sealed end of the cannula, 1 to 3 small holes were opened on the wall of the cannula. The steel cannula was inserted into each artery so that the small holes were covered with the proximal end of the artery, and this proximal end was fixed to the cannula by a thin thread. The isolated, cannulated artery was placed in a bath, which was maintained at constant temper ature of 37'C, and was perfused with