Modification of enzyme activities concerned with collagen metabolism in the heart of spontaneously hypertensive and aortic-constricted rats.

The activities of three enzymes concerned with collagen metabolism 4-prolyl hydroxylase, UDP-glucose: collagen glucosyltransferase and glucosyl-galactosyl-hydroxylysine glucohydrolase and 4-hydroxyproline content have been studied in the cardiac ventricles of spontaneously hypertensive rats (SHR) during prehypertensive, hypertensive and sustained hypertensive stages (respectively 4.5, 12 and 19 weeks of age). They were compared with values observed in age-matched normotensive Wistar Kyoto rats (WKY). The same studies have been performed in parallel on aortic-constricted rats (ACR) 8 days after suprarenal constriction of the abdominal aorta. The most striking finding was a significant increase in cardiac prolyl hydroxylase specific activity in the ACR but not in the SHR. No variation in 4-hydroxyproline concentration was found in the hearts of ACR. In contrast, a decrease in 4-hydroxyproline concentration was found in the hearts of SHR at 19 weeks. Cardiac glucosyltransferase specific activity was significantly elevated only in the SHR at 12 weeks. No variation in glucohydrolase specific activity was detected in the hearts of either SHR or ACR. The cardiac enzyme activities all decreased with age. These data show that the alterations in cardiac collagen metabolism are different in SHR and ACR. The patterns of the alterations found in the heart mirror those observed in the aorta in both models under the same experimental conditions.