Absorption and metabolism of radioactive cobalt compounds through normal and wounded skins

As the result of an accident in which a human being was contaminated with carrier-free 58Co on a considerable surface area of his skin, some uptake of the activity into the body was identified. Preliminary experiments with rats indicated that carrier-free 58Co may be absorbed through the skin whereas per os administration of the activity did not show enough absorption in the GI tract. Experiments with guinea-pigs revealed that absorption of carrier-free 58Co tartarate through skin damaged by stripping with Scotch tape was considerable. As much as about 50% of the dose applied on the skin surface was absorbed after one day. Intact skin that had been shorn and slightly shaven absorbed less than 10% of the applied activity and plucked skin absorbed between 10 and 20% of the applied dose. The activity absorbed through the skin was mostly excreted in the urine as was also the activity after intravenous administration, whereas the activity administered per os mostly appeared in the faeces. A double-tracer method using the chloride of 57Co and 60Co (not carrier-free) indicated that intact skin on the back of adult rats strongly prevented absorption of the Co compound applied, whereas stripped skin absorbed the compound to the same extent as that found after intra- and sub-cutaneous injections. Several pieces of evidence indicate that the most important barrier against the absorption of radioactive compounds of the cobalt on the skin is the corneal layer of the epidermis. Another factor that modifies the absorption considerably is the chemical form of the compound: chlorides are readily absorbed and hydroxides are only slightly absorbed. (author)