Island-Cell Tumors in Irradiated Rats in Parabiosis. ∗

Abstract

The incidence, function and age and sex distribution of adenomas and carcinomas of the islands of Langerhans were studied in Deac-Slonaker rats. These lesions are very rare in rats, and we have not encountered them in normal control rats of this or other strains. In the course of experiments to determine the effects of a single supralethal dose of radiation on duration of life and incidence of tumors we parabiosed young inbred littermate rats of this strain. The technique, described elsewhere(1), was to irradiate one of the pair some weeks after parabiosis and when equilibrium had been established between the animals. The right-hand rat received a single supralethal dose of 1000 r of 250 KV X-rays. The left-hand rat was shielded. The LD₃₀ for single rats is 750 r. Parabiosis protects the supralethally irradiated animal from death and from the most marked effects of the acute radiation syndrome. Parabiosis in itself provides an abnormal hormonal balance in the animals, which is accentuated by the irradiation of one. We found tumors of the islands of Langerhans rarely in control parabiotic rats, commonly in the irradiated partner. The animals were allowed to live until dead or moribund.

For this study 715 pairs of parabiont rats were chosen at random, but with life spans of over 200 days after operation or irradiation. One hundred thirteen pairs of these parabiosed animals, approximately equally divided as to sex, were used as controls. Of the irradiated pairs 276 were male to male parabionts, 326 female to female. The findings are set out in Tables I and II. Males are strikingly prone to develop these pancreatic tumors.

Morphology. The tumors of the islands are usually large enough to be seen grossly (0.4 to 1.2 cm).