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 pro- tein 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 METHODSRadioactive materials.14C-Labelled materials were ob- tained from the Radiochemical Centre, Amersham.