title: Effects of zeranol on protein turnover in L6 myotubes.
abstract: Protein synthesis and degradation were measured in cultures of L6 myotubes to determine the direct anabolic activity of zeranol on muscle. Zeranol, dexamethasone, insulin and zeranol-dexamethasone combination, at various concentrations from 10(-8) to 10(-6) M, were added to cultures at either 18 hr prior to or at the beginning of a 6 hr synthesis or degradation measuring period. Protein synthesis was measured by determining the incorporation of radioactivity into trichloraoacetic acid precipitable cell protein following incubation with [3H] leucine. Protein synthesis was expressed as cpm incorporated in 6 hr per mg protein. Protein degradation was measured by a pulse-chase procedure using [3H] leucine. Protein degradation was expressed as the percent labeled protein degraded in 6 hr. Results from the study indicate that zeranol did not stimulate protein synthesis or inhibit proteolysis (P greater than .01). Stimulation of proteolysis observed with 10(-8) M dexamethasone was 13% and 18% (P less than .01) at the 6 hr and 24 hr incubation period, respectively. Dexamethasone-stimulated protein degradation was not altered appreciably by zeranol. In contrast, 10(-6) M insulin significantly (P less than .01) stimulated protein synthesis (16%) and inhibited protein degradation (15%). These results suggest that the anabolic action of zeranol does not occur by directly regulating muscle protein synthesis or degradation, or by altering the glucocorticoid-induced catabolic response in muscle.
authors.affiliation: Department of Animal Science, University of Idaho, Moscow 83843.
authors.forename: R A
authors.initials: RA
authors.lastname: Roeder
authors.forename: J M
authors.initials: JM
authors.lastname: Gunn
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000378:metabolism; D009132:Muscles / Q000187:drug effects; D051381:Rats; D012118:Resorcinols / Q000494:pharmacology*; D013997:Time Factors; D015029:Zeranol / Q000494:pharmacology*
chemical_list: D007328:Insulin; D009124:Muscle Proteins; D012118:Resorcinols; D015029:Zeranol; D003907:Dexamethasone