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Effects of Divalent Cations on K⁺ Transport in Rat Liver and Morris Hepatoma 5123tc¹

Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada

Slices of normal rat liver and of liver and tumor from rats with subcutaneously implanted Morris hepatoma 5123tc were cooled to induce loss of K⁺, and net uptake of K⁺ was studied during subsequent incubation at 37°C. Initial K⁺ concentration per unit of dry weight was about 50% higher in the hepatoma than in normal or host liver. Cooling induced an equal loss of K⁺ from all three tissues. Rewarming produced rapid net uptake of K⁺ by tumor slices, which attained equilibrium levels within 10 min. There was an initial lag period in liver slices which was longer with host liver. The maximum rate of net uptake of K⁺ was lower than that of tumor in both liver preparations, especially host liver. Addition of 0.5% ethylene-diaminetetraacetic acid or 10^-4 M g-strophanthin to the incubation medium caused a decrease in net K⁺ uptake in all three tissues. Omission of Ca⁺⁺ from the medium decreased K⁺ uptake in normal and host liver slices but not in hepatoma. Omission of Mg⁺⁺ appeared to decrease K⁺ uptake only in host liver. The higher rate of K⁺ uptake in hepatoma slices, but not the higher initial K⁺ concentration, may be related to the greater cellularity of the tumor.

¹ This work was supported by grants from the National Cancer Institute of Canada, and the Foster Bequest of the University of Toronto, and by a Fellowship of the National Cancer Institute of Canada (R. A. H.)

² Present address: Department of Physiology and Pharmacology, University of Saskatchewan, Saskatoon, Canada.

Received 8/17/67. Accepted 6/17/68.