Protocollagen proline hydroxylase activity in rat heart during experimental cardiac hypertrophy.

Cardiac hypertrophy was produced in rats by constricting the abdominal aorta subdiaphragmatically. The weight of the left ventricle was significantly elevated 2 days after aortic constriction and was 19% higher than in shamoperated animals at 11 days. The activity of protocollagen proline hydroxylase (PPH), an enzyme participating in collagen biosynthesis, and the hydroxyproline content of the heart muscle were determined. PPH activity was increased at 2 days after aortic constriction and declined thereafter, being still above the control level at 11 days. The hydroxyproline content of the left ventricle was significantly increased at 11 days in hypertrophied heart muscle compared to controls. The present results suggest diat in cardiac hypertrophy an early connective tissue activation occurs. Later, this leads to connective tissue accumulation. The increased collagen content may give support to the cardiac muscle contracting against systolic overload.