Anabolic effects of catecholamines in diaphragm muscle from hypophysectomized rats.

Abstract

In contrast to its traditional role as a catabolic agent, epinephrine added to diaphragm muscle from hypophysectomized (hypox) rats stimulated three different processes that reflect accumulation of substances in peripheral tissue: uptake of an amino acid, α-aminoisobutyric acid (AIB), uptake of a monosaccharide, 3-O-methyl-glucose, and the incorporation of leucine and tyrosine into protein. In buffer containing 1 mg/ml ascorbate to retard oxidation of catecholamines, the minimal effective concentrations were 10-7 M for AIB transport and 5 × 10-9 M for tyrosine incorporation. Norepinephrine was less potent, but it, too, stimulated AIB transport and tyrosine incorporation. One catabolic process, glycogenolysis, was also enhanced in hypox rat diaphragms, which initially responded between 10-8-10-7 M epinephrine. On the other hand, in diaphragms from intact rats, it was necessary to raise the concentration of epinephrine to 5 × 10-4 M to stimulate AIB transport, but tyrosine incorporation was never increased....