Effect of insulin on the tissue distribution of thallium-201

Translocation of potassium under the influence of insulin has been repeatedly demonstrated by various investigators during the past 50 years. Accordingly, it is expected that insulin administration would affect the distribution pattern of the potassium analogue thallium-201. To test the validity of this assumption, the present study was performed on 46 rabbits, with an average weight of 3.9 +- 0.8 pounds. To study the effects of the factors involved in the administration of insulin and its dosage, the rabbits were divided into groups; each group being studied on a separate day. The experimental animals were sacrificed exactly 10 minutes after the intravenous injection of radiothallium. The results of the present study showed that thallium-201 uptake per gram tissue varied from one batch to another. However, the radioactivity uptake per gram by the different organs showed a constant pattern. Among the organs studied, the highest level of radioactivity per gram was encountered in the kidneys and heart, followed by the lungs. Then came the liver and lastly the striated muscles. Insulin administration caused an increase in the radioactivity uptake in all the organs studied. The magnitude of this increment was highest in the heart, kidneys and lungs; moderate in the liver, and slight in the striated muscles. In addition, the effect of insulin occurred at an optimum time that varied with the route of administration and was dose related up to a certain level. (author)