NONSYNCHRONOUS CHANGES IN MYOCARDIAL COLLAGEN MESSENGER-RNA AND PROTEIN DURING AGING - EFFECT OF DOCA-SALT HYPERTENSION

Myocardial fibrosis has been investigated in 3-, 16-, and 24-mo-old no rmal rats and also in 24-mo-old rats subjected to deoxycorticosterone acetate (DOCA)-salt treatment-induced-hypertension. Collagen content w as assessed both histologically and by hydroxyproline assay. Type I an d III procollagen mRNA levels were quantitated by Slot Blot analyses. Aging is associated with fibrosis as shown both biochemically (hydroxy proline concentration in 3-, 16-, and 24-mo-old rats was 0.70 +/- 0.05 , 0.92 +/- 0.07, and 1.57 +/- 0.13 mg/g of left ventricle, respectivel y, P < 0.05 and P < 0.0001 vs. 3 mo) and histologically. By contrast, type I procollagen mRNA levels decreased during aging (from -63%, P < 0.001 in 16-mo-old rats and -51%, P < 0.01 in 24-mo-old rats vs. 3-mo- old rats) as well as type III procollagen mRNA levels. DOCA-salt treat ment in 24-mo-old rats had no effect on either the degree of fibrosis or the mRNA levels. We conclude that nonsynchronous changes in myocard ial collagen mRNA and protein occur during aging, indicating translati onal and/or posttranslational mechanisms in collagen regulation. Hyper tension during senescence did not modify collagen deposition at either the protein or mRNA levels.