EFFECT OF NICOTINE ON CAPILLARY FLOW AND TERMINAL VASCULAR CAPACITY OF THE HEART IN NORMAL DOGS AND IN ANIMALS WITH RESTRICTED CORONARY CIRCULATION

¹ Department of Medicine, Wayne State University School of Medicine, Detroit, Michigan

Effects of a single i.v. infusion and repeated i.m. injections of nicotine on capillary blood flow and terminal vascular capacity of the heart were compared in dogs with and without experimentally induced impairment of coronary circulation. Gradual coronary artery narrowing was produced by means of ameroid constrictors placed around the three main coronary arteries. Capillary blood flow and terminal vascular capacity were determined simultaneously from the activities of Rb⁸⁶ and I¹³¹-albumin, respectively, employing a differential counting technique. Results indicate that in dogs with normal coronary curculation, a single infusion of nicotine increases both capillary blood flow and terminal vascular capacity; repeated nicotine administration, however, has no significant effect on either. In contrast, in animals with impaired coronary circulation, both the single i.v. infusion and repeated administration of nicotine resulted in a fall in capillary blood flow but an increase in terminal vascular capacity. These findings suggest that impaired coronary circulation resulting from coronary artery constriction alters the response of coronary vasculature to nicotine.