Hormone dependence of the L and M isozymes of pyruvate kinase in isolated rat hepatocytes

Abstract

L Pyruvate kinase (LPK) is considered to be the major form in the liver. Two isozymes, LPK and MPK, have been localized in the isolated rat hepatocyte in vitro with an immunocytometric method. MPK is induced by insulin, which also creates a slight stimulation of LPK (at physiological doses) in both fed and fasted animals. Glucagon inhibits LPK in fed animals (the fasting rat is already in a situation of gluconeogenesis and this hormone is ineffective). MPK is insensitive to glucagon, regardless of the nutritional state of the animals. Each PK isozyme is thus controlled predominantly by one of the two hormones, corresponding to a sophisticated regulation of hepatic glycolysis and gluconeogenesis.

Immunohistological demonstration of pyruvate kinase isoenzyme type L in rat with monoclonal antibodies.

“…Hepatocytes devoid of LPK could not be observed in any of our liver specimens. This result is in contrast to the presence of non-reacting cells in cytospin preparations of isolated hepatocytes, which was also observed by Gali et al (1983). The reason for this discordance may be a preparative damage to these cells during the long isolation procedure inducing leakage of cytoplasmic components including LPK.…”

Physicochemical and Immunochemical Proofs of Short-Term Insulin Regulation of Hepatic M(2) Pyruvate Kinase

“…Isolation and incubation of hepatocytes were pre viously described [3,4] and are carried out here by the same technique with slight modifications: sometimes, 2 or 3 rats were used for the same experiment. To maintain the viability of the cells from the first rats, they were gassed with a mixture including 95 % 02 and 5% CO2 during the isolation of hepatocytes from other rats.…”

“…Cellulose acetate strips were supplied by Cello-In previous papers, two of us have shown in vivo, in human pathologic liver [1], then in rat experiments [2] and in vitro, the insulin dependence of the M2 pyruvate kinase (PK) isozyme using an original immunocytometric method with isolated rat hepatocytes [3,4], Enzyme assay, cellulose acetate electrophore sis and electroimmunodiffusion are used to check these data by physicochemical meth ods.…”