生长激素刺激肝切片中前体掺入蛋白质和核酸的氨基酸需求。

Amino acid requirement for the growth-hormone stimulation of incorporation of precursors into protein and nucleic acids of liver slices.

作者信息

Clemens M J, Korner A

出版信息

Biochem J. 1970 Oct;119(4):629-34. doi: 10.1042/bj1190629.

DOI:10.1042/bj1190629

PMID:5493500

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1179447/

Abstract

Incorporation of [(14)C]leucine into protein in rat liver slices, incubated in vitro, increased as the concentration of unlabelled amino acids in the incubation medium was raised. A plateau of incorporation was reached when the amino acid concentration was 6 times that present in rat plasma. Labelling of RNA by [(3)H]orotic acid was not stimulated by increased amino acid concentration in the incubation medium. 2. When amino acids were absent from the medium, or present at the normal plasma concentrations, no effect of added growth hormone on labelling of protein or RNA by precursor was observed. 3. When amino acids were present in the medium at 6 times the normal plasma concentrations addition of growth hormone stimulated incorporation of the appropriate labelled precursor into protein of liver slices from normal rats by 31%, and into RNA by 22%. A significant effect was seen at a hormone concentration as low as 10ng/ml. 4. Under the same conditions addition of growth hormone also stimulated protein labelling in liver slices from hypophysectomized rats. Tissue from hypophysectomized rats previously treated with growth hormone did not respond to growth hormone in vitro. 5. No effect of the hormone on the rate or extent of uptake of radioactive precursors into acid-soluble pools was found. 6. Cycloheximide completely abolished the hormone-induced increment in labelling of both RNA and protein. 7. It was concluded that, in the presence of an abundant amino acid supply, growth hormone can stimulate the synthesis of protein in rat liver slices by a mechanism that is more sensitive to cycloheximide than is the basal protein synthesis. The stimulation of RNA labelling observed in the presence of growth hormone may be a secondary consequence of the hormonal effect on protein synthesis. 8. The mechanism of action of growth hormone on liver protein synthesis in vitro was concluded to be similar to its mechanism of action in vivo.

摘要

在体外培养的大鼠肝切片中，[(14)C]亮氨酸掺入蛋白质的量随着培养液中未标记氨基酸浓度的升高而增加。当氨基酸浓度达到大鼠血浆中氨基酸浓度的6倍时，掺入量达到平台期。培养液中氨基酸浓度升高并未刺激[(3)H]乳清酸对RNA的标记。2. 当培养液中没有氨基酸或氨基酸浓度处于正常血浆浓度时，未观察到添加生长激素对前体标记蛋白质或RNA有影响。3. 当培养液中氨基酸浓度为正常血浆浓度的6倍时，添加生长激素可使正常大鼠肝切片蛋白质中相应标记前体的掺入量增加31%，RNA掺入量增加22%。在低至10ng/ml的激素浓度下即可观察到显著效果。4. 在相同条件下，添加生长激素也可刺激垂体切除大鼠肝切片中的蛋白质标记。先前用生长激素处理过的垂体切除大鼠的组织在体外对生长激素无反应。5. 未发现该激素对放射性前体摄取到酸溶性池中的速率或程度有影响。6. 环己酰亚胺完全消除了激素诱导的RNA和蛋白质标记增加。7. 得出结论，在有丰富氨基酸供应的情况下，生长激素可通过一种比基础蛋白质合成对环己酰亚胺更敏感的机制刺激大鼠肝切片中的蛋白质合成。在生长激素存在下观察到的RNA标记刺激可能是激素对蛋白质合成作用的次要结果。8. 得出结论，生长激素在体外对肝脏蛋白质合成的作用机制与其在体内的作用机制相似。