Changes in collagen synthesis and degradation during skeletal muscle growth

Abstract

The changes in collagen metabolism during skeletal muscle growth were investigated by measuring rates of synthesis and degradation during stretch-induced hypertrophy of the anterior latissimus dorsi muscle of the adult chicken (Gallus domesticus). Synthesis rates were obtained from the uptake of tritiated proline injected intravenously with a flooding dose of unlabeled proline. Degradation of newly synthesized and "mature" collagen was estimated from the amount of hydroxyproline in the free pool as small molecular weight moieties. In normal muscle, the synthesis rate was 1.1 +/- 0.3%/day, with 49 +/- 7% of the newly produced collagen degraded rapidly after synthesis. During hypertrophy there was an increase of about fivefold in the rate of synthesis (P less than 0.01), a 60% decrease in the rate of degradation of newly synthesized collagen (P less than 0.02), and an increase of about fourfold in the amount of degradation of mature collagen (P less than 0.01). These results suggest an important role for degradative as well as synthetic processes in the regulation of collagen mass. They indicate that enhanced degradation of mature collagen is required for muscle growth and suggest a physiological role for the pathway whereby in normal muscle, a large proportion of newly produced collagen is rapidly degraded.

Regulation of procollagen metabolism in the pressure-overloaded rat heart.

“…It should be pointed out, however, that the estimation of procollagen synthetic and intracellular procollagen degradative rates by this technique is dependent upon a number of theoretical and practical assumptions, as outlined by McAnulty and Laurent (24) and Karim et al ( 15 ). Nevertheless, a similar decrease in procollagen Fr was noted by Laurent et al (36) during skeletal muscle hypertrophy and by Turner et al (37) during RV hypertrophy after bleomycin-induced lung injury. At present, little is known about the intracellular sites and regulatory events that might modify the susceptibility of newly synthesized procollagens to intracellular proteolysis in vivo.…”

Lamina cribrosa thickening in early glaucoma predicted by a microstructure motivated growth and remodeling approach

“…Collagen fibrils are thought to be constantly removed and deposited in the LC. We hypothesize that an upregulated synthesis or downregulated degradation of collagen fibrils may alter the collagen content and cause the volumetric growth of collagenous tissues (Laurent et al, 1985, 1978; Bhole et al, 2009). The thickening of the LC seen in early experimental glaucoma is thus assumed to be a consequence of collagen fibril mass increase stimulated by the elastic stretch experienced by the collagen fibril material.…”

Effects of Aging on Muscle Fibers and Collagen Content of the Diaphragm: A Comparison with the Rectus abdominis Muscle

“…The changes in CSA and fiber-type distri bution in the DIA and RA muscles may explain in some events the decline in muscle performance such as the reduction in isomet ric force and the rate of contraction and increase in time to peak tension [1,2,5,21], It has been known that skeletal muscle has interstitial spaces where collagen is the princi pal structural component [23] with the re sponsibility of transmitting tensile muscle strength to the tendons and which positively influences passive force but negatively affects maximum total strength. Little is known re garding changes in the collagen and elastic fiber systems of skeletal muscle as a function of aging.…”