Aorta Collagen Metabolism in Spontaneously Hypertensive and Aortic-Constricted Rats: Variations in Enzyme Activities Concerned with Disaccharide Unit Synthesis and Degradation According to Blood Pressure and Age

Two enzyme activities concerned with collagen disaccharide unit metabolism (UDP-glucose: collagen glucosyltrans ferase and glucosyl-galactosyl-hydroxylysine glucohydrolase) have been studied in the thoracic aortic wall together with 4-prolyl hydroxylase activity and 4-hydroxyproline content in spontaneously hypertensive rats (SHR) at the prehypertensive, hypertensive and sustained hypertensive stages (respectively 32 days, 12 weeks 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. Negative regressions of all three specific activities as function of age were observed. The most striking difference observed between the SHR and the WKY was the increase of glucosyltransferase specfic activity, already found at the prehypertensive stage and continuing thereafter; the glucohydrolase specific activity was increased only during the establishment of hypertension whereas no modification was found with prolyl hydroxylase at any stage. However, a diminution of hydroxyproline concentration was seen at all ages while total hydroxyproline mass remained unaffected. The alterations of the aortic collagen metabolism observed in the ACR recall those seen in the SHR at the prehypertensive stage: the only significant modification was that of glucosyltransferase activity. Correlation was found between glucosyltransferase activity and blood pressure level in the two animal models.