EFFECT OF COBALT DEPLETION ON GROWTH AND COBALT RETENTION IN ORGANS AND TISSUES OF THE RAT

In two experiments with weaned rats initially weighing 31 g Co-58 was supplied i. m. in a single dose of approximately 100 kBq into the dors al side of the left thigh. In the following 19 days the distribution o f the isotope in the organism and the excretion kinetics were evaluate d. In experiment 1, the pattern of distribution of Co-58-activity were monitored during growth by continuous determination of the activities in faeces as well as in urine in ten animals and also in various orga ns and tissues at day 3, 7, 11, 15 and 19 after the application of the isotope in a total of 25 animals. At day 1, already 66 % of the injec ted activity was excreted by the renal and 3 % by the faecal route. Du ring the 19 days total loss accounted for 98 % of the activity adminis tered with 87 % of that in the urine and 13 % in the faeces. The highe st concentration of activity was measured in liver and kidneys, the hi ghest Co-58-content was found in the residual carcass accounting for 5 9 % of total carcass activity. From the site of injection Co-58 was re leased very fast, and no significant difference between left and right thigh occurred throughout the whole experiment. The calculations for estimation of the steady state showed a constant distribution of the c obalt isotope already after the third day. The proportions of urinary and faecal excretion of total excretion indicated similar properties. In experiment 2, the effect of a different oral cobalt supply on the k inetics of Co-58 was observed in 32 animals, which were divided into 5 treatment groups. The animals wer fed a semisynthetic diet depleted o f cobalt, which was supplemented with 0, 10, 50,250 and 1250 ppb cobal t. Also in this experiment, the highest concentration of activity was measured in liver and kidneys. A significant treatment effect was foun d in the level of body retention of Co-58. Increasing the cobalt suppl y to the highest level (1250 ppb Co) resulted in a decrease of the act ivity of organs and tissues. This difference was significant for liver , kidneys, spleen, testes and distal small intestine. Kinetics of faec al and urinary activity loss were similar to experiment 1, an effect o f cobalt supplements could not been observed.