Creatine turnover in the starry flounder,Platichthys stellatus.
Starry flounder (Platichthys stellatus) were cannulated and a bolus of 9 μCi(14)C-creatine in saline was injected into the caudal vein. The fish were sacrificed at intervals ranging from 1h to 36d after label injection. Creatine pool size (PCr+Cr) and creatinine (Crn) content in blood, muscle, gills and liver were analyzed and specific activities (SA) determined.Mean concentrations of PCr+Cr/Crn in PCA-extracts of muscle, gills, liver and blood of experimental fish (at rest) were 38.1/2.40, 4.1/0.25, 5.6/0.45 and 0.3/n.d. μmol.g(-1) respectively.Within 10 min, plasma SA had decreased by approximately 90%. In white muscle, the rate of(14)C-Cr appearance as well as label disappearance was slow compared to gills and liver. In fish examined 36d postinjection, mean SA in muscle had decreased to 23% of maximum SA which occurred 24h after injection.(14)C-Cr was incorporated into the liver tissue at a very high rate, SA being two orders of magnitude higher in liver than in white muscle. Over the first 6d, retention of label was observed in liver; after 36d only 3% of the original label was detected.Creatine pool size (PCr+Cr) in white muscle decreased with food deprivation. In flounder sacrificed after 36d, PCr+Cr was only 52% that of fed control fish, suggesting that creatine or precursors for its biosynthesis are supplied with the diet.
Department of Zoology, University of British Columbia, 6270 University Boulevard, V6T 2A9, Vancouver, B.C., Canada.
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Danulat
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Hochachka