Smooth Muscle Cell Proliferation in the Ductus Arteriosus and the Descending Aorta, and Effects of Enalapril on SMC Proliferation in Perinatal Rats

Abstract

This study was carried out to determine the proliferation profile of the smooth muscle cells (SMC) in the media of the ductus arteriosus (DA) and the descending aorta (Ao), and to examine the effects of the angiotensin-converting enzyme inhibitor enalapril on the proliferation of these cells in perinatal rats. The proliferating cell nuclear antigen (PCNA) index of the DA peaked in 19-day-old fetuses at 75%, and the index significantly declined in 20-day-old fetuses. The PCNA index of the Ao showed a similar profile until pups reached 1 day of age; however, the index of the Ao then increased in 3-day-old pups. The PCNA indices of the DA and Ao decreased significantly after maternal oral treatment with enalapril (10 mg/kg for 7 days), with a more marked decline in the DA than in the Ao. The PCNA indices of these vessels in 20-day-old fetuses were not altered by maternal treatment with enalapril. These results indicate that the SMC proliferation rate in the DA was similar to that in the Ao until pups reached the age of 1 day, and that the inhibitory effect of enalapril on the SMC proliferation was age-dependent and more prominent in the DA than in the Ao.