AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 1 153-R161, Copyright © 1996 by American Physiological Society
Regeneration and revascularization of a nerve-intact skeletal muscle graft in the spontaneously hypertensive rat
R. C. Carlsen, D. Kerlin and S. D. Gray
Department of Human Physiology, School of Medicine, University of California, Davis 95616, USA.
Skeletal muscles in hypertensive subjects develop an increased resistance
to insulin that reduces their ability to incorporate glucose and synthesize
glycogen. Insulin is an anabolic hormone in muscle, and muscle insulin
receptors bind the growth factor, insulin-like growth factor I (IGF-I), an
important contributor to muscle development and regeneration. An increase
in insulin resistance in hypertensive subjects might produce muscle atrophy
and weakness or limit regenerative growth after injury. Regenerative muscle
growth was assessed in 24-to 26-wk-old spontaneously hypertensive rats
(SHR) and Wistar-Kyoto (WKY) rats by subjecting extensor digitorum longus
(EDL), an ankle flexor, to a nerve-intact graft procedure. The procedure
produces extensive muscle fiber and capillary degeneration, but has little
effect on the muscle nerve. Muscle morphology and contractile function were
examined in intact and regenerating EDL at 21, 42, and 63 days postgraft.
Muscle revascularization was assessed histologically at the same time
points. Severe established hypertension did not prevent the reestablishment
of a structurally normal capillary network in injured muscles. SHR muscle
fiber regeneration and maturation, however, were significantly depressed
compared with WKY grafts. The reduced regenerative recovery of SHR EDL in
adult animals with severe hypertension does not appear to be due to a
failure to restore the muscle nerve or capillary network, but may reflect a
reduced anabolic response to insulin or IGF-I.
