Smooth muscle cell proliferation in the ductus arteriosus and the descending aorta, and effects of enalapril on SMC proliferation in perinatal rats

This study was carried out to determine the proliferation profile of the sm ooth muscle cells (SMC) in the media of the ductus arteriosus (DA) and the descending aorta (Ao), and to examine the effects of the angiotensin-conver ting enzyme inhibitor enalapril on the proliferation of these cells in peri natal rats. The proliferating cell nuclear antigen (PCNA) index of the DA p eaked 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 unti l 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 ves sels in 20-day-old fetuses were not altered by maternal treatment with enal april. 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 th e inhibitory effect of enalapril on the SMC proliferation was age-dependent and more prominent in the DA than in the Ao.