Protein synthesis and amino acid accumulation during development in the rat: dissociation of diaphragm and heart muscle sensitivity to insulin.
Insulin is released into the circulation early during fetal life, but the physiological significance of the hormone in the fetus is still unclear. The present study was undertaken to evaluate the possible effects of insulin on the protein metabolism of skeletal and heart muscle during the perinatal period in the rat. When incubating hemidiaphragm in a bicarbonate buffer, 0.1 U/ml ox insulin failed to enhance the incorporation of leucine-4,5-3H into muscle protein before birth and during the immediate neonatal period. From 3 days of age onwards a stimulatory effect of insulin on protein synthesis was constantly observed. While insulin thus was ineffective in promoting protein synthesis in hemidiaphragms before the third postnatal day, it significantly enhanced the synthesis in heart muscle at an earlier stage of development. Insulin stimulated the uptake of alpha-aminoisobutyric acid-1-14C into the diaphragm muscle during late fetal life as well as through the early neonatal period. The role of insulin in protein metabolism during fetal life may thus be limited to the augmentation of amino acid transport in skeletal and heart muscle and to a stimulatory effect on protein synthesis only in certain tissue(s), e.g. heart muscle.
D000375:Aging; D049148:Aminoacylation / Q000187:drug effects*; D000818:Animals; D000831:Animals, Newborn; D003964:Diaphragm / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D005260:Female; D005333:Fetus; D006321:Heart / Q000187:drug effects / Q000254:growth & development; D007328:Insulin / Q000494:pharmacology*; D007930:Leucine / Q000378:metabolism; D024510:Muscle Development; D009124:Muscle Proteins / Q000096:biosynthesis*; D009206:Myocardium / Q000378:metabolism*; D011247:Pregnancy; D014176:Protein Biosynthesis / Q000187:drug effects*; D051381:Rats
D007328:Insulin; D009124:Muscle Proteins; D007930:Leucine