Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Because prominent skeletal muscle dysfunction and muscle wasting are seen in both chronic uremia and in primary hyperparathyroidism, and because markedly elevated parathyroid hormone levels occur in both disorders, potential effects of parathyroid hormone on skeletal muscle protein, amino acid, and cyclic nucleotide metabolism were studied in vitro using isolated intact rat epitrochlearis skeletal muscle preparations. Intact bovine parathyroid hormone and the synthetic 1-34 fragment of this hormone stimulated the release of alanine and glutamine from muscle of control but not from chronically uremic animals. This stimulation was dependent upon the concentration of parathyroid hormone added: At 10(5) ng/ml parathyroid hormone increased alanine release 84% and glutamine release 75%. Intracellular levels of alanine and glutamine were not altered by parathyroid hormone. Increasing concentrations of the 1-34 polypeptide decreased [(3)H]leucine incorporation into protein of muscles from both control and uremic animals. Using muscles from animals given a pulse-chase label of [guanido-(14)C]arginine in vivo, parathyroid hormone increased the rate of loss of (14)C label from acid-precipitable protein during incubation and correspondingly increased the rate of appearance of this label in the incubation media. Parathyroid hormone increased muscle cAMP levels by 140% and cGMP levels by 185%, but had no effect on skeletal muscle cyclic nucleotide phosphodiesterase activities as assayed in vitro. Adenylyl cyclase activity in membrane preparations from control but not uremic rats was stimulated by parathyroid hormone in a concentration-dependent fashion. However, no stimulation of guanylyl cyclase activity was noted by parathyroid hormone, although stimulation by sodium azide was present. Incubation of muscles with added parathyroid hormone produced a diminished responsiveness towards epinephrine or serotonin regulation of amino acid release and cAMP formation in the presence compared to the absence of parathyroid hormone. In the absence of parathyroid hormone, detectable inhibition of alanine and glutamine release was produced by 10(-9) M epinephrine, whereas in the presence of parathyroid hormone (1,000 ng/ml) inhibition of alanine and glutamine release required 10(-6) M or greater epinephrine. Resistance to cyclic AMP action as well as inhibition of cyclic AMP formation by parathyroid hormone was found. Preincubation of rat sarcolemma with 1-34 parathyroid hormone produced a decreased activity of the isoproterenol-stimulable adenylyl cyclase activity but there was no apparent change in the concentration of isoproterenol required for one-half maximal and maximal stimulation of the enzyme. These findings suggest that high levels of parathyroid hormone have direct effects on skeletal muscle protein, amino acid, and cyclic nucleotide metabolism in muscle of normal but not uremic animals. Treatment with these high levels of parathyroid hormone in vitro appears to reproduce in normal muscle, the metabolic deficits and loss of hormone responsiveness observed in muscle of chronically uremic animals. It is therefore possible that direct effects of parathyroid hormone on skeletal muscle may account in part for the muscle dysfunction and wasting of primary hyperparathyroidism and chronic uremia.
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PMID:Effects of parathyroid hormone on skeletal muscle protein and amino acid metabolism in the rat. 630 55

Muscular dystrophies are characterized by primary wasting of skeletal muscle for which no satisfactory therapy is available. Studies in animal models have shown that stem cell-based therapies may improve the outcome of the disease, and that mesoangioblasts are promising stem cells in this respect. The efficacy of mesoangioblasts in yielding extensive muscle repair is, however, still limited. We found that mesoangioblasts treated with nitric oxide (NO) donors and injected intra-arterially in alpha-sarcoglycan-null dystrophic mice have a significantly enhanced ability to migrate to dystrophic muscles, to resist their apoptogenic environment and engraft into them, yielding a significant recovery of alpha-sarcolgycan expression. In vitro NO-treated mesoangioblasts displayed an enhanced chemotactic response to myotubes, cytokines and growth factors generated by the dystrophic muscle. In addition, they displayed an increased ability to fuse with myotubes and differentiating myoblasts and to survive when exposed to cytotoxic stimuli similar to those present in the dystrophic muscle. All the effects of NO were cyclic GMP-dependent since they were mimicked by treatment with the membrane permeant cyclic-GMP analogue 8-bromo-cGMP and prevented by inhibiting guanylate cyclase. We conclude that NO donors exert multiple beneficial effects on mesoangioblasts that may be used to increase their efficacy in cell therapy of muscular dystrophies.
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PMID:Ex vivo treatment with nitric oxide increases mesoangioblast therapeutic efficacy in muscular dystrophy. 1715 15