Gylcine-14C incorporation into the plasma membrane proteins of normal and regenerating liver

Incorporation of 14C-glycine in plasmatic membrane proteins of the intact and regenerating liver was studied at the beginning of G1 period of the cell cycle. The electrophoretic study of 0.05 M Na2CO3 soluble plasmatic membrane proteins of the regenerating liver showed that maximal incorporation of 14C-glycine was associated with the proteins having molecular weight of about 60 000. The pattern of incorporation of 14C-glycine in different fractions of 0.05 M Na2CO3 insoluble proteins of the plasmatic membranes of the intact and regenrating liver did not differ essentially.     

Effect of formate on 14C incorporation from various precursors into rat liver proteins and lipids

Experiments on the rat liver homogenates and slices show that formate stimulates carbon incorporation from [1-14C] lysine and [2-14C] acetate into proteins and from [2-14C] acetate into lipids. The stimulating effect depends on both the formate concentration and nature of the labelled precursor. The in vitro experiments demonstrate the highest stimulating effect on the metabolism of both proteins and lipids under administration of 2 microM formate per 100 g of animal mass. Determination of the label incorporation rate at different time after formate administration showed that the latter evokes an intensified synthesis of protein with rate of its decay remaining the same.     

Effects of dietary nonspecific nitrogen on [14C]glutamate and [14C]proline incorporation into bone proteins in chicks

The incorporation of [14C]glutamic acid into EDTA-soluble and -insoluble calvaria protein in vitro and [14C]proline into EDTA-insoluble femur protein in vivo was determined in chicks fed inadequate and adequate levels of nonspecific nitrogen (glutamic acid). In each instance, the amount of amino acid incorporated into bone protein was reduced by the low level of nonspecific nitrogen. It was concluded that the high incidence of leg abnormalities observed in chicks fed purified diets containing adequate levels of indispensable amino acids but lacking in total nitrogen might be associated with an inability to form bone matrix protein.     

Leucine catabolism and incorporation into tissue proteins in thyroparathyroidectomized rats

We investigated parameters of leucine metabolism in thyroparathyroidectomized (TPX) and pair-fed control rats using a technique of continuous infusion of [l-14C]leucine. The rate of leucine turnover was significantly smaller in TPX than in control rats (42.5 +/- 2.6 vs 35.1 +/- 1.9 mumole/hr/100 g, mean +/- SEM, six rats). There was no significant difference between rates of alpha-decarboxylation of leucine by the two groups of rats. The protein incorporation of leucine was significantly smaller in the muscle of TPX than control rats (39 +/- 5 vs 24 +/- 4 pmole/mg protein, mean +/- SEM, six rats) but in liver it was not significantly different. Thyroparathyroidectomy also had no significant effect on concentration of either leucine or its ketoacid (alpha-ketoisocaproate) in plasma, liver, and muscle. We conclude that hypothyroidism does not alter catabolism of leucine but reduces its incorporation into muscle protein.     

Effect of hydrocortisone and insulin on (14C)-glycine and (3H)-methionine incorporation into spleen proteins in alloxan-diabetic rats

The intensity of labelled amino acid incorporation into spleen total proteins of albino rat with experimental diabetes was studied as influenced by hydrocortisone, insulin and both hormones simultaneously. Hydrocortisone inhibits and insulin stimulates the [14C] glycine and [3H] methionine incorporation into total proteins of alloxan-diabetic rat spleen. Under simultaneous administration of both hormones the inhibitory hydrocortisone effect is allayed by insulin. It is suggested that an increased level of glucocorticoid hormones in blood is one of the reasons of protein metabolism disturbance under diabetes mellitus.