Food intake alters muscle protein gain with little effect on na, k
-atpase and myosin isoforms in suckled rats.
Fiorotto, Marta L., and Teresa A. Davis.
USDA/ARS Children's Nutrition Research Center, Department of
Pediatrics, Baylor College of Medicine, Houston, TX 77030
APStracts 3:0410R, 1996.
Biochemical maturation accompanies the rapid accretion of skeletal
muscle in early life. We wished to determine whether changes in
muscle protein accretion, induced by variations in food intake
altered the biochemical maturation of the soleus and the extensor
digitorum longus (EDL) muscles. Rat pups were suckled in litters of
4, 10, or 16 to induce differences in food intake. At 21 d of age,
muscle protein and DNA were quantitated and biochemical maturation
was assessed from measurement of [3H]ouabain-binding site abundance
and myosin isoform composition. Differences in food intake produced a
twofold range in body and muscle weights, and protein and DNA
contents. Protein accretion was more sensitive to nutrient intake in
the soleus than in the EDL. Serum 3-5,3'-triiodothyronine (T3) and
insulin concentrations decreased with a reduction in food intake.
Total ouabain-binding sites were not altered in either muscle, and
were independent of muscle size. Differences in myosin isoform
composition were more pronounced for the soleus than the EDL, but
relatively small in magnitude. These results demonstrate that,
whereas postnatal muscle protein accretion and circulating hormone
concentrations are sensitive to food intake, the biochemical
maturation is resilient. The immature muscle does not exhibit the
fiber-type-specific responses to malnutrition typical of mature
muscle.
Received 8 October 1996; accepted in final form 7 November 1996.0
APS Manuscript Number R815-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996