The effect of insulin on incorporation of amino acids into protein of normal rat diaphragm in vitro

Abstract

Sinex, MacMullen & Hastings (1952) found that, when insulin was added in vitro to diaphragm from normal non-fasting rats incubated in a medium containing DL-[1-14C]alanine but lacking an easily oxidizable substrate such as glucose or pyruvate, the transfer of 14C from the alanine into protein in the diaphragm was increased. Similar observations with [ 1-14C]glycine in place of alanine were made by Krahl (1953). Sinex et al. (1952) found that transfer was less if glucose or pyruvate was present in the medium when no insulin had been added, and that in the presence of glucose or pyruvate addition of insulin raised to only a small extent incorporation into diaphragm protein of 14C from the alanine. But Krahl (1953), on the other hand, observed that incorporation of 14C from [1-14C]glycine into protein of normal fasting rat diaphragm in vitro was raised by the addition of glucose alone to the medium, the presence of insulin in the medium in addition to glucose having no significant effect. Since these results were of importance with respect to the relative effects of insulin on carbohydrate and protein metabolism (see Ketterer, Randle & Young, 1957), we have repeated the experiments of these authors and extended their observations to include a variety of labelled amino acids. MATERIALS AND METHODS Radioactive materials. 14C-Labelled materials were obtained from the Radiochemical Centre, Amersham.

The stimulation by thrombin of glucose oxidation in human platelets.

“…Protein synthesis was estimated by a modification of the method of Manchester and Young (21). Platelets were incubated with 1 ,uc of uniformly labeled leucine-14C (0.004 jumole) in 1.5 ml of Krebs-Ringer bicarbonate buffer and 1 ml of 0.85% saline at 370 C for 1 hour in an atmosphere of 95%y O2-5%o C02.…”

Physiologic hyperinsulinemia stimulates protein synthesis and enhances transport of selected amino acids in human skeletal muscle.

“…An insulin stimulatory effect on muscle protein synthesis has been clearly shown in different experimental conditions (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). Insulin also decreases the proteolytic activity of lysosomes (11), but recent evidence suggests that the bulk of muscle protein is degraded by a different pathway that is not under insulin control (12)(13)(14).…”

Metabolic and Ultrastructural Changes Induced in Adipose Tissue by Insulin

“…Not the least of these components might be those that comprise the cell's surface membrane which, as a result of vesicle formation, might be undergoing constant renewal. In this connection it should be noted that the addition of insulin in vitro has been found to increase the rate of incorForation of labeled amino acids into proteins (40)(41)(42)(43) and of radioactive phosphorus into phospholipids and nucleic acids (35). In the case of amino acid incorporation into protein, the accelerating action of insulin has been demonstrated under conditions in which an increased entry of the amino acid into the tissue has been excluded as an explanation for this effect (43).…”