AJP - Endocrinology and Metabolism, Vol 242, Issue 2 87-E92, Copyright © 1982 by American Physiological Society
Arginine metabolism and urea synthesis in cultured rat skeletal muscle cells
W. M. Pardridge, L. Duducgian-Vartavarian, D. Casanello-Ertl, M. R. Jones and J. D. Kopple
Skeletal muscle is known to contain arginase, but, because this enzyme is
also present in erythrocytes, the exact origin of arginine-derived
ornithine in peripheral tissues is uncertain. In the present studies,
skeletal muscle cells obtained from regenerating hindlimb muscle of adult
rats were grown in primary tissue culture for approximately 3 wk and then
studied in regard to changes in medium amino acid concentrations over a
48-h period. The consumption of arginine and serine was observed in
parallel with the production of ornithine, proline, citrulline, glycine,
and urea. Medium threonine and methionine concentrations were relatively
constant over 48 h. Incubation of muscle cells with [U-14C]arginine
resulted in the formation of [14C]ornithine and [14C]proline at rates at
least 10-fold greater than could be accounted for by enzyme constituents of
fetal calf serum. In addition, [guanido-14C]arginine was converted to
[14C]urea and [U-14C]serine was converted to [14C]glycine. These studies
indicate that cultured skeletal muscle cells contain a high arginase
capacity and actively synthesize ornithine and urea from arginine.
