肥満, 高脂血ラット (Zucker Fatty Rat) におけるインスリン作用の特異性に関する研究 [II]:"脂肪細胞におけるインスリン特異結合能と結合インスリンの生物効果"

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概要

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• The correlation between insulin-binding to receptor and biological activity of bound insulin was simultaneously studied with the same epididymal fat cells of Zucker fatty rats and their thin littermates or wild type normal rats. Fat cells were prepared from the Zucker fatty rats (10-11 months old, body weight 600-700 g) and from their thin littermates or normal rats (9-12 months old, body weight about 300 g). The amount of bound insulin and the rate of glucose oxidation were determined in the same isolated fat cells after incubation with various concentrations of <SUP>125</SUP>I-insulin with the constant specific activity for estimation of insulin dose response, or with U-<SUP>14</SUP>C-glucose of increasing carrier glucose concentration, in order to quantitate the glucose effect. Cells were equilibrated with 95% O<SUB>2</SUB> : 5% CO<SUB>2</SUB> and incubated for one hour at 37°C in Krebs-Ringer-bicarbonate buffer without bovine serum albumin (pH=7.4). The insulin bound to fat cells were separated from free insulin by isolation of fat cells. The biological activity was estimated by measuring the rate of conversion of U-<SUP>14</SUP>C-glucose into <SUP>14</SUP>CO<SUB>2</SUB> or <SUP>14</SUP>C-Lipid per cell per hour. <BR>The following results were obtained. <BR>1) The glucose conversion to CO<SUB>2</SUB> increased proportionally to medium glucose concentration on fat cells of both fatty and control rats. The dose response of glucose oxidation rate was greater in the Zucker fatty rat cells than in the control rat cells in use increasing concentration of medium glucose. On the other hand, when medium insulin concentration was increased, the proportional increment of glucose conversion to CO<SUB>2</SUB> was not so extentive in fat cells of Zucker fatty rats as in the control fat cells. <BR>2) On Zucker fatty rats and control rats, the conversion rate of glucose into CO<SUB>2</SUB>, as an index of the biological activity of insulin, was not proportional to the amount of bound insulin. <BR>3) Insulin binding capacity <I>per cell</I> in Zucker fatty rats was not lower than in control rats under the biological range of glucose and insulin concentration. <BR>In conclusion, mechanism of insulin resistance in Zucker fatty rats should be partially attributed to the abnormality of intracellular steps of glucose metabolism.

• 一般社団法人 日本内分泌学会の論文

著者

• 上田 賀美

  和歌山県立医科大学内科内分泌部門

関連論文

• 肥満, 高脂血ラット (Zucker Fatty Rat) におけるインスリン作用の特異性に関する研究 [II]:"脂肪細胞におけるインスリン特異結合能と結合インスリンの生物効果"
• 肥満, 高脂血ラット (Zucker Fatty Rat) におけるインスリン作用の特異性に関する研究 [I]:"脂肪細胞Insulin Receptorの結合能力並びにProinsulin存在下のInsulin親和性について"

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