In situ morphometric analysis of the coronary arterial growth in perinatal rats

The perinatal changes in the diameters of left and right coronary arteries in rats were studied using the rapid whole body freezing technique. The main portion of the left coronary artery and left anterior descending and circumflex branches rapidly increased in diameter after birth as well as ascending aorta. The ratios of the diameters of the left coronary artery and anterior descending branch to the diameter of ascending aorta increased significantly after 4 days of age. In contrast, there were no significant changes in the diameter of the right coronary artery from the fetus to the 8-day-old pups and the ratio of the right coronary artery to the ascending aorta significantly decreased after birth. We report here that the left coronary artery in rats increases in diameter more rapidly than the right coronary artery in the early newborn period.