Incorporation of H3-Thymidine into the DNA of Melanotic and Amelanotic Melanoma Explants after Whole-Body X-Irradiation of Melanoma-Bearing Platyfish-Swordtail Hybrids

Abstract

Melanoma-bearing platyfish-swordtail hybrids have been whole-body irrated with x-rays, and the H3-thymidine incorporation into the DNA of melanome explants has been determined after various times of cultivation. Whilr melanomas of non-irradiated control fish continues to incorporate labelled thymidine into DNA during the whole cultivation period of 20 hours, the melanomas of x-irradiated fish showed a drastic inhibition of H3-thmidine incorporation already after few hours of cultivation. This suppression of DNA synthesis, which was more distinct in amelanotic melanomas of albino hybrids than in melanotic melanomas of pigmented hybrids, is consistent with the finding that x-irradiation of melanome-bearing fish causes a temporary regression of melanoma growth. The data also confirm that the two melanoma types differ in growth rate and radiosensitivity. Due to the higher content of proliferating cells, the rapidly growing amelanotic melanomas incorporated more labelled thymidine into DNA and are more radiosensitive than the less rapidly growing melanotic melanomas