Skeletal Muscle Protein and Amino Acid Metabolism in Experimental Chronic Uremia in the Rat

Abstract

A B S T R A C T The kinetics and factors regulating alanine and glutamine formation and release were investigated in skeletal muscle preparations from control and experimentally uremic rats. These preparations maintained phosphocreatine and ATP levels in vitro which closely approximated levels found in vivo. Alanine and glutamine release from uremic muscle were increased 45.8

Effects of Parathyroid Hormone on Skeletal Muscle Protein and Amino Acid Metabolism in the Rat

“…Epitrochlearis preparations were also obtained from rats made chronically uremic by unilateral nephrectomy and subtotal ligation of the branches of the contralateral renal artery as described in detail in Methods. These muscle preparations had an increased rate of alanine and glutamine release in the absence of added parathyroid hormone, as has been described previously (10). In contrast to the effect of parathyroid hormone on control muscle preparations, amino acid release from epitrochlaris preparations obtained from uremic rats was not altered by either intact 1-84 parathyroid hormone or the 1-34 fragment.…”

“…Skeletal muscle preparations from rats made chronically uremic by surgery release large quantities of alanine and glutamine in vitro. This appears to result, in part, from an increased rate of protein degradation in muscles from uremic animals (10,11). Since both chronic renal insufficiency and hyperparathyroidism are associated with substantial elevations in the circulating levels of parathyroid hormone, and since both disease states have a significant muscle dysfunction and wasting disorder associated with them, a relationship between the elevated levels of parathyroid hormone and the disordered skeletal muscle metabolism of both disease complexes seems possible.…”

“…Since both chronic renal insufficiency and hyperparathyroidism are associated with substantial elevations in the circulating levels of parathyroid hormone, and since both disease states have a significant muscle dysfunction and wasting disorder associated with them, a relationship between the elevated levels of parathyroid hormone and the disordered skeletal muscle metabolism of both disease complexes seems possible. For these reasons, we have investigated the effects of parathyroid hormone and its synthetic As described previously (10), epitrochlearis preparations were obtained from chronically uremic and control SpragueDawley rats (TIMCO, Houston, TX). Animals were made chronically uremic by unilateral nephrectomy and ligation of two branches of the renal artery of the contralateral kidney.…”

“…Incorporation of radiolabeled amino acid into skeletal muscle protein was assayed by the appearance of 3H label in the acid-insoluble pellet of the trichloroacetic acid extract of the muscle (10). The frozen incubated muscle was homogenized in 12% trichloroacetic acid, centrifuged, and the pellet washed twice with 5% trichloroacetic acid.…”

“…Although cyclic nucleotide levels were determined after 2, 5, 10, and 20 min of incubation with each agonist, only the data for 2-min incubations with epinephrine, 5 min with parathyroid hormone, and 10 min with serotonin are presented because these periods produced the greatest observed increments in cyclic nucleotide levels. Estimations of adenylyl and guanylyl cyclase activities in skeletal muscle homogenates were based on the determination of (10). The cAMP formed was isolated by a minor modification (16) Lowry (18).…”