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KMID : 0358719650020010001
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Korean Journal of Biochemistry
1965 Volume.2 No. 1 p.1 ~ p.10
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Insulin-I^(131) Spaces of various Tissues of Rabbit
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Abstract
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After single injection of insulin-I´31 (30´ -60Pc) via the ear vein of rabbit blood samples were withdrawn at the interval of 10 or 30 minutes for 2 hours. Every plasma samples were divided into 2 fractions. i, e, TCA precipitable fraction and TCA soluble fraction. The radioacfivity of each fraction was measured in order to determine the variation of distribution of insulin-P31 injected in the plasma with time course. Two hours after injection of insulin-I13´ animals were sacrificed and various tissues were excised. Weighed tissue was minced with 10% TCA solution in the mortor and divided into 2 fractions by centrifugation. Each fraction of tissue homogenate was counted for radioactivity by means of well type seintillation counter,
Insulin-P31 spaces in various tissues were calculated by obtaining the ratios of radioactivities of TCA precipitable fractions of tissues to that of plasma. On the other hand, I´31spaces, which is the distribution spaces of degradated products of injected insulin-P31 were calculated with ratios of radioactivties of TCA soluble fractions of tissues to that of plasma.
The result of this investigation was as follows;
1. The radioactivity of TCA precipitable fraction of plasma showed initially higher value and decreased exponentially. Thirty munutes after injection of insulin-I´31 values were relatively constant throughout the experimental period, On the other hand, radios ctivitiy of TCA soluble fraction of plasma, which is the split products of injected insulin-1131 rose during first 30 minutes and remained almost constant plateau value. These constant plateau value was refered to calculate the insulin-I13´ and I131 spaces in the various tissues.
2. Insulin-I13´ space in the kidney tissue was
showed most highest value and averaged about 526 1%, There were similar values between spleen, lung and skin tissues in insulin-I13´ space showing about 70% of tissue weights. Heart, liver, smooth muscle and uterus tissue showed same order of insulin-I13´ space, averaging about 50% of tissue weights. However, membrane permealility of insulin-I13i would be negligible in the smooth mucele and uterus because of their sizes of extracellular spaces. Insulin-P31 spaces in the skeletal muscle and adipose tissue were same order of size of extracellular space, therefore the effect of insulin on these tissues would be surface mechanism on cell membrane rather than intracellular mechanism. In the brain tissue, insulin-I´3´ space was less than extracellular space. It seems that insulin can not travel through blood-brain barrier.
3. In order to observe the degradation of insulin in various tissues, I131spaces were determined by radioactivities of TCA soluble frations of tissues comparing with that of plasma.
I´33 spaces were 375. 1 % in the kidney, 233. 5 % in the spleen and 125. 9 % in the liver. In above 3 tissues, radioactivities of TCA soluble fractions were more concentrated than in the plasma. It seems that these tissues would be principal sites of insulin degradation:
Though I13´ space in the adipose tissue was near 100%, this higher value is not due to the de-gradation of insulin in the adipose tissue but radio-activities of TCA soluble fraction were equilibrated with that of plasma because insulin-I´3´ space of adipose tissue was almost same with extracellular space.
In the other tissues, I131 spaces were similar with their own sizes of extracellular spaces.
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