Changes in collagen biosynthesis, types, and mechanics of aorta in hypertensive rats

The purpose of this study was to relate changes in collagen composition with the mechanical properties of aortas of spontaneously hypertensive rats (SHRs). SHRs and normal Wistar-Kyoto (WKY) rats were killed at ages 6 and 20 weeks, and their aortas were removed. A portion of each aorta was used for determination of passive mechanical properties, and the remainder was incubated with carbon 14-labeled proline containing medium for 18 hours at 37 degrees C. After incubation, the tissues were lyophilized, and aliquots were used for sequential extraction with neutral salt, acetic acid, and pepsin at 4 degrees C. The pepsin extracts that contained most of the collagen were used for characterization of the collagen types and synthesis of collagen by the production of [14C]-labeled hydroxyproline. Collagen concentration decreased approximately 16% in both 6- and 20-week-old aortas, but collagen synthesis was about twofold higher in the aortas from both 6- and 20-week-old SHRs. Although type V collagen represented a minor fraction of total collagen (5%) in the aortas of WKY rats, it was twofold greater in the hypertensive animals. This increment in type V collagen in SHR aortas was accompanied by a reduction in the proportion of type I collagen, with no change in the proportion of type III. Study of the passive mechanical properties of the tissues showed that SHR aortas were stiffer compared with aortas of WKY rats, with a larger difference at 20 weeks than at 6 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)