Homeostasis of zinc and iron in mouse B16 melanoma.

a subcutaneous implantation of maccrated tumor bits (mela noma B16) into the right axillary region by a Becton Dickin son BD13 needle. Tumor growth was divided into three periods, according to tumor size. Using 65 Zn and 59 Fe, the homeostasis of zinc and iron in mice with melanomas was studied at 5†" 6days (unde tectable tumor), 10 days (medium-size tumor), and 18†" 20 days (large-size tumor, no metastasis). Radioisotopes. Carrier-free 65 Zn (International Chemical and Nuclear Inc.) and ferrous citrate @ Fe (specific activity, 24.4 mc/mg, Abbott, Inc.) were diluted with 0.1 N HC1 (10 pc/mi). Whole-Body Turnover of 65 Zn and @ Fe. Mice were injected i.p. with 65 @ (1 pc/mouse) or @ Fe (1 .5 pc/mouse) 6 days after transplantation, and whole-body radioactivity was as sayed by a well-type scintillation detector for a 13-day period. Each mouse was placed into a 50-mi plastic tube which was filled with sponge gauze to maintain a constant counting ge ometry. It was necessary to hold the gauze in place because the animal tended to displace the gauze. The initial whole body radioactivity was counted at 1 hour after injection of 65 Zn or @ Fe. The whole-body counts at various postinjection times were expressed as percent of initial counts. Organ Retention of 65 Zn and @ Fe. At the end of the whole-body turnover study, the animals were decapitated. Parts of the pancreas, liver, blood, tumor, and the entire spleen, kidney, testis, and femur were excised, rinsed in saline, blotted on sponge gauze, and transferred into a pretarred 10-mi plastic culture tube. The organ weight was recorded, and the radioactivity was assayed by a well-type scintillation detec tor. Cpm/gm of tissue were converted to dpm/gm and cx pressed as percent of initial whole-body dpm. The organ reten tion of 65 Zn or @ Fe in mice with melanomas then was cx pressed as percent of control. Organ Uptake of 65Zii and 59Fe. Mice were injected i.p. with 65 Zn (1 pc/mouse) or @ Fe (1.5 pc/mouse) at 5, 10, and 18 days after tumor transplantation and were decapitated 1 hour later. Radioactivity in the pancreas, liver, spleen, kidney, testis, blood, tumor, and whole femur was assayed as decribed above. Cpm/gm of tissue were converted to dpm/gm and then organ radioactivity in mice with melanomas was expressed as percent of control. Dialysis of Spleen 59Fe. To evaluate whether …