The metabolism of isolated fat cells. IV. Regulation of release of protein by lipolytic hormones and insulin.
The metabolism of isolated fat cells. IV. Regulation of release of protein by lipolytic hormones and insulin.
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发表时间：
1966-09
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通讯作者：
M. Rodbell
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作者：
M. Rodbell
用~（14）C-组氨酸或~（14）C-亮氨酸标记大鼠附睾脂肪垫脂肪细胞蛋白质。随后用激素处理细胞后，检查标记蛋白的命运。释放标记的蛋白质刺激脂解激素（促肾上腺皮质激素，胰高血糖素，肾上腺素）和茶碱。蛋白质水解，作为测量三氯乙酸可溶性放射性介质中的外观，发生在很小的程度上，但不受脂解激素。这些非颗粒酶如苹果酸脱氢酶、葡萄糖6-磷酸脱氢酶、乳酸脱氢酶和己糖激酶的释放也被脂解激素增强。在完整的脂肪组织中，脂解激素对酶的释放具有与在分离的脂肪细胞中观察到的相同的作用。蛋白质的释放是次要的脂肪酸的细胞内浓度的上升，在响应脂解激素。脂肪酸，而不是它们的过氧化物，负责蛋白质的释放。分离的脂肪细胞在培养基中的白蛋白被脂肪酸饱和后释放蛋白质。当组织中的脂肪酸浓度达到约16 µeq/g时，完整的脂肪组织释放酶以响应脂解激素。对于分离的脂肪细胞，通过在培养基中提供过量的白蛋白或向细胞供应葡萄糖来防止细胞内脂肪酸的积累和蛋白质释放，特别是在胰岛素存在下，这加速了细胞内脂肪酸的再酯化。有人建议，脂肪组织的代谢能力，在体外和体内，调节部分由细胞蛋白质的释放介导的细胞内浓度的脂肪酸，这是产品的胰岛素和脂解激素的相反的行动。
Abstract Proteins of fat cells, isolated from rat epididymal fat pads, were labeled with 14C-histidine or 14C-leucine. The fate of the labeled protein was examined after subsequent treatment of the cells with hormones. Release of labeled proteins was stimulated by lipolytic hormones (adrenocorticotropic hormone, glucagon, and epinephrine) and by theophylline. Proteolysis, as measured by the appearance in the medium of trichloracetic acid-soluble radioactivity, occurred to a small extent but was not influenced by lipolytic hormones. Release of such nonparticulate enzymes as malic dehydrogenase, glucose 6-phosphate dehydrogenase, lactic dehydrogenase, and hexokinase was also enhanced by lipolytic hormones. In intact adipose tissue, lipolytic hormones had the same effect on release of enzymes as observed with isolated fat cells. Release of protein was secondary to the rise in intracellular concentration of fatty acids in response to lipolytic hormones. Fatty acids, not their peroxides, were responsible for the release of protein. Isolated fat cells released protein after albumin in the medium became saturated with fatty acids. Intact adipose tissue released enzymes in response to lipolytic hormones when the concentration of fatty acids in the tissue reached approximately 16 µeq per g. With isolated fat cells, accumulation of intracellular fatty acids and protein release were prevented by either providing an excess of albumin in the medium or supplying glucose to the cells, especially in the presence of insulin, which accelerated re-esterification of intracellular fatty acids. It is suggested that the metabolic capacity of adipose tissue, in vitro and in vivo, is regulated in part by the release of cellular protein mediated through the intracellular concentration of fatty acids which is the product of the opposing actions of insulin and lipolytic hormones.