EFFECT OF CALCITONIN GENE-RELATED PEPTIDE ON WELL-DEVELOPED CANINE CORONARY COLLATERAL VASCULATURE

This study was performed to examine the effect of calcitonin gene-rela ted peptide (CGRP) on blood flow through well-developed coronary colla teral vessels. Studies were performed in 9 adult mongrel dogs 4-6 mont hs after embolic occlusion of the left anterior descending coronary ar tery (LAD) with a hollow intravascular plug to stimulate collateral ve ssel growth. At the time of study, the LAD was cannulated to determine interarterial collateral flow from measurement of retrograde blood fl ow. Radioactive microspheres were injected during retrograde flow coll ection to determine continuing tissue flow in the collateral dependent region. CGRP was infused into the left main coronary artery in a dose of 0.2 mug/kg/min to reach collateral vessels originating from the le ft coronary system. Retrograde blood flow was 40 +/- 9 ml/min during b asal conditions and increased 22 +/- 9% in response to infusion of CGR P (n = 9, p < 0.05). Tissue flow to the collateral-dependent myocardia l region did not change in response to CGRP infusion. Isolated rings o f epicardial collateral vessels contracted with prostaglandin F2alpha (PGF2alpha) underwent relaxation in response to CGRP which was similar in magnitude to that of normal coronary arteries of comparable size. These data demonstrate that CGRP causes vasodilation of well-developed epicardial coronary collateral vessels, resulting in an increase in c ollateral blood flow.