1. 1. Gluconeogenesis was studied in isolated avian hepatocytes. The highest rate of glucose production obtained was from lactate, followed by dihydroxyacetone, glyceraldehyde, and fructose. Alanine was converted to glucose at only about 4% the rate of lactate. 2. 2. Addition of 10mM sorbitol, xylitol, or ethanol to the hepatocytes increased glucose production from pyruvate 25-40%, while glycerol addition increased it only 9%. 3. 3. Addition of β-hydroxybutyrate had no effect on glucose production from lactate or pyruvate. 4. 4. Addition of octanoate had no effect on glucose production from pyruvate, but depressed it from lactate at 5 mM. 5. 5. Differences in the formation of glucose from various substrates suggest some basic differences in the mode of glucose production between the chick and the rat and guinea-pig.
|Original language||English (US)|
|Number of pages||6|
|Journal||Comparative Biochemistry and Physiology -- Part B: Biochemistry and|
|State||Published - 1979|
Bibliographical noteFunding Information:
Glucose production in avian liver has been reported to differ from that in mammals, In contrast to the rat and the guinea-pig, Soling et al. (1973) has found that isolated perfused pigeon liver does not produce glucose from pyruvate. Sarkar (1971) and Davison & Langslow (1975) have shown that, in vivo, chickens do not utilize pyruvate or alanine to increase blood glucose levels. Glycerol is converted to glucose at one-half the rate of lactate in isolated guinea-pig hepatocytes (Arinze & Rowley, 1975), but only at 3~°o the rate of lactate in chicken hepatocytes (Dickson & Langslow, 1977). The influence of fl-hydroxybutyrate and fatty acids on glucose production also differs by species. /~-Hydroxybutyrate increases the conversion of lactate to glucose in perfused rat liver (Arinze et al., 1973), but depresses that in guinea-pig liver (Arinze & Rowley, 1975). In the perfused rat liver, fatty acids stimulate glucose production from lactate and pyruvate (Wil-liamson et al., 1969; Soling, 1974; Arinze et al., 1973), but in rabbit hepatocytes and perfused guinea-pig liver, octanoate inhibits the conversion of lactate to glucose and stimulates the conversion of pyruvate to glucose (Zaleski & Bryla, 1977; Arinze et al., 1973). In perfused pigeon liver, fatty acids have no effect on glucose production from lactate or pyruvate (Soling & Kleineke, 1976). These differences among species might be explained in part by the intracellular compartmentation of a key gluconeogenic enzym~phosphoenolpyruvate car-boxykinase (PEPCK, E.C. 126.96.36.199). In the rabbit and chick, the enzyme is primarily mitochondrial, while * This study was supported in part by NIH AM 18957 and GM 01818. DRR is the recipient of Career Development Award KO4 AM 00112. The present address for LJB is Division of Diabetes and Metabolism, 75E. Newton, University Hospital, Boston, Massachusetts 02118. Michigan Agricultural Experiment Station Journal Article No. 8587.
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