The Effects of Acute Norepinephrine-Induced Hypertension on the Coronary Arteries of Newborn Piglets

Newborn piglets were subjected to 45 min of sustained norepinephrine-induced hypertension and then monitored for 4 hr at baseline conditions. They were then sacrificed and the anterior descending coronary artery was serially sectioned for study by light and electron microscopy. Other groups were sacrificed after 72 and 168 hr of baseline conditions. Changes were limited to the endothelium and subendothelial intima of the most proximal segment of the anterior descending coronary artery. As similar changes are normally present in perinatal piglets, the experimental animals were compared with sham-operated controls to determine if there was a modification of the naturally occurring congenital lesions. Although the prevalence of coronary lesions in control and experimental animals was not significantly different, the experimental groups showed unique features. At 4 hr, there was marked intimal edema and disruption of the endothelium with fragmentation and dissolution of the internal elastic lamina. There was selective invasion of the intima by platelets and monocytemacrophages. After 72 and 168 hr, there was an increase and progression in preexisting modified smooth muscle cell plaques in which there developed prominent fibroplasia and collagenization. It is proposed that acute hypertension may be responsible for these changes. Such perinatal surges in blood pressure may be involved in the initiation of atherogenesis.