脂肪組織における糖質代謝の研究:特に血中インシユリン相當値の測定について
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The author has attempted to establish basic experimental conditions suitable for metabolic studies, including bioassay of insulin-like activity of blood, of epididymal fat pad excised from Wistar strain rats. Ca. 100-120gm. weighing rats were used for the experiments. Epididymal adipose tissues were incubated by means of Warburg's apparatus in Krebs-Ringer's bicarbonate solution. Glucose and vorious hormones were added to the media and tested for their effect upon glucose uptake and QCO<SUB>2</SUB>.<BR>In the first step, the experiments were made on the comparative studies of different tissue sections of the epididymal fat pad with regard to their influences upon glucose uptake, QCO<SUB>2</SUB> and QO<SUB>2</SUB>. A trisection pooled method as described in the figure was found to give most constant results, hence, this method was used throughout the whole experimental series. For the standard metabolic response of epididymal fat pad, glucose uptake and QCO<SUB>2</SUB>, particularly the glucose uptake, were chosen.<BR>Using this trisection method, insulin, glucagon, ACTH, cortisone acetate, sodium fluorate and malonic acid were tested for their effects on the glucose uptake and QCO<SUB>2</SUB> of the incubating adipose tissues.<BR>As regards to the insulin effect, detailed studies were carried out to build up a bioassay method of minute insulin dose added to the incubation medium. ΔGlucose uptake and QCO<SUB>2</SUB> of incubated adipose tissues, particularly of the former, showed variations corresponding to the insulin dosage added to the medium, indicating dose-response relationship. Thus a bioassay method of minute insulin dosage could be deduced by the determination of <I>Δ</I>glucose uptake from the incubation medium.<BR>Using this bioassay method insulin-like activity of normal subjects and diabetic patients were determined in comparison with the results of rat diaphragm method.<BR>The results are summarized as follows :<BR>1) It has been proved that the isolated epididymal fat pad of rat is a suitable model for the study of carbohydrate metabolism of the tissues as in the case of the rat diaphragm. The glucose uptake and QCO<SUB>2</SUB> of the isolated epididymal fat pad responded quite well to insulin addition. Glucagon acted similarly but gave a mild effect upon glucose uptake and QCO<SUB>2</SUB>, whereas the pituitary and adrenocortical hormones exhibited no apparent effect. Sodium fluorate and malonic acid apparently inhibited glucose uptake and QCO<SUB>2</SUB> of fat pad. Insulin effect upon epididymal fat pad could be accelerated by glucagon. But the effect was markedly suppressed with ACTH, cortisone acetate, sodium fluorate and malonic acid, particularly of the latter two.<BR>2) A relation corresponding to linear regression was confirmed between the <I>Δ</I>glucose uptake from the incubation medium and the log dose of insulin added to the medium. This insulin effect was observed with an insulin concentration up to 10<SUP>-5</SUP>unit/ml, thus making it possible to determine quantitatively the insulin-like activity of serum in terms of Δglucose uptake. The mean insulin-like activity of serum in 13 normal subjects was 3.72±2.97 × 10<SUP>-4</SUP>unit/ml. The mean insulin-like activity of serum in 12 diabetics was 2.66±2.18×10-4unit/ml.<BR>3) In the comparative studies, the rat diaphragm showed much more basal glucose uptake than epididymal fat pad, whereas the latter exhibited much more 4glucose uptake expressed as insulin effect. These results seem to point upon a higher sensitivity of epididymal fat pad in the bioassay of insulin-like activity.<BR>4) Insulin was added to normal or diabetic serum and their insulin effect was examined to see how the effect of exogenous insulin is influenced by human serum. In the case of normal serum,
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