COLLAGEN CHARACTERIZATION IN VOLUME-OVERLOAD-INDUCED AND PRESSURE-OVERLOAD-INDUCED CARDIAC-HYPERTROPHY IN MINIPIGS

Previous studies in several different species have shown reduced extractability of collagens in some types of cardiac hypertrophy (volume overload) but not others (pressure overload). The objective of the present study was to examine collagen proteins from the same species (minipigs) with both pressure-overload- and volume-overload-induced cardiac hypertrophy. Hypertrophy was induced by two methods: thoracic banding of the aorta to create pressure overload and arteriovenous shunt to cause volume overload in a porcine model. Collagen types I, III, IV, and V were isolated by pepsin digestion from normal and hypertrophied pig left ventricle tissues. Types I and III collagens from normal and hypertrophied samples, when separated from types IV and V, were digested with cyanogen bromide (CB), and the peptides were examined. Collagen concentration was increased in myocardium removed from hearts subjected to volume overload and unchanged in hearts subjected to pressure overload. The extractability of total collagen was unaffected in pressure-overloaded left ventricles but lower in samples from volume-overloaded hearts. CB digestion cleaved all of the types I and III collagens into similar smaller CB peptides with the exception of a 100-kDa peptide that was observed in both control and hypertrophied hearts. This peptide corresponds to one of the high-molecular-weight peptides found in canine heart tissue. The. mature collagen cross-link hydroxylysylpyridinoline (HP) was identified in normal and hypertrophied types I and III collagen from porcine sources. Pressure-overload- and volume-overload-induced cardiac hypertrophy in the pig produced different alterations in the extracellular matrix. Collagen concentration was increased in hearts from arteriovenous fistula animals but not pressure-overload animals. Reductions in extraction of collagens were also observed in the fistula model but not in the pressure overload of animals.