Angiotensin II and left ventricular growth in newborn pig heart

The left ventricle of the neonatal pig heart is a model of rapid physiological cardiac growth that is dependent upon accelerated ribosome formation and increased RNA content. The goals of the present study were to investigate the role of angiotensin II in this rapid growth. Hearts from 3 d old control piglets or piglets that were treated with enalapril maleate, an angiotensin converting enzyme inhibitor, or DuP 753, an angiotensin II receptor antagonist, were used for measurements of left ventricular mass, RNA, DNA and protein. Hearts from enalapril-treated pigs also were used for measurements of rates of ribosome formation and total protein synthesis during perfusion as modified Langendorff preparations. Treatment of piglets with enalapril maleate resulted in decreased left ventricle/body wt ratio, RNA content, total RNA and total protein in the left ventricle. These parameters were unaffected in the right ventricle. In vitro perfusion of hearts from enalapril-treated piglets revealed decreased ribosome formation and total protein synthesis in the left ventricle. Piglets treated with DuP 753 had decreased left ventricle/body wt ratio as well as decreased RNA content, total RNA and RNA/DNA ratio in the left ventricle. These results suggest that angiotensin II may be required for rapid growth of neonatal pig hearts.