DNA synthesis in coronary collaterals after coronary artery occlusion in conscious dog

With 3Hthymidine, DNA synthetic activity in coronary collateral arterioles was assessed in dogs subjected to progressive stenosis of the left circumflex coronary artery for different periods (36 h-5 days). Coronary flow, reactive hyperemia, and pressure gradient (aortic pressure, peripheral coronary pressure) were measured. Normal animals and animals with sham operations served as controls. Labeling of nuclei was seen in seven of the constricted dogs. Proliferative activity was highest at the level of the smallest diameters of the collateral vessels (midzone). There was heavy labeling in intima and media. Adventitial and myocardial mesenchymal cells also incorporated 3Hthymidine. No radioactive DNA was found in control animals. The data suggest that the active growth process in collaterals after constriction of the left circumflex coronary artery appears early, as there is evidence of collateral growth after 36 h of constriction. Peak growth as evidenced by 3Hthymidine incorporation was reached when the occlusion period was 4 days.