ENERGY SOURCES FROM PROTEIN SYNTHESIS AND ENZYMATIC SECRETION IN RAT PANCREAS IN VITRO

The main characteristics of rat pancreas energy metabolism in vitro have been established, and the relations between protein synthesis and this metabolism have been studied with the use of well-known inhibitors (oligomycin, antimycin, dinitrophenol, oxamate, fluoride, anaerobiosis). Krebs-Ringer Tris-HCl-buffered medium, supplemented with glucose and amino acid mixture, afforded the optimal conditions for incubation of rat pancreas pieces. Under these conditions a metabolic steady state was maintained for more than 2 h. Carbamylcholine and pancreozymine stimulated chymotrypsinogen and amylase secretion and oxygen uptake, and depressed leucine incorporation into proteins of the rat pancreatic pieces. Mitochondria supplied more than 90% of the energy of the pancreas; the ATP pool of the gland was renewed at least every 23 sec, and the respiratory control had a minimal value of 3.8. Glycolysis, which accounted for less than 10% of the energy output under normal conditions, supplied as much as 30% of control value in anaerobiosis. The effects of inhibitors of respiration and of glycolysis on amino acid incorporation into proteins suggest that protein synthesis depends on a common pool of ATP supplied by glycolysis and oxidative phosphorylation and that it is very sensitive to reduction of this pool. Oligomycin and oxamate did not inhibit the carbamylcholine-induced secretion, but anaerobiosis and the combination of oligomycin and oxamate did. These data suggest that stimulated secretion requires an ATP supply, if not an increase of the ATP generation. Strong reduction of ATP output by antimycin, oxamate with anaerobiosis or the combination of oligomycin and oxamate increased the spontaneous release of chymotrypsinogen, suggesting that retention of the enzymes in the cell is also dependent on a minimal energy supply. © 1969.