A Comparison of the Effects of Hyperthermia on Cell Growth in Human T and B Lymphoid Cells: Relationship to Alterations in Plasma Membrane Transport Properties

Abstract

Hyperthermic exposure (39-43 degrees C) for 1 or 2 hr impairs growth and Na+-dependent amino acid transport in both a radiosensitive human T (Molt-4) and a radioresistant B (RPMI 1788) lymphoid cell line. The heat damage to Na+-dependent amino acid transport in both cell lines is reversible under the conditions tested. Cell growth, as judged by increases in cell number, is decreased in both cell lines after hyperthermic treatment (43 degrees C, 1-hr exposure). This decrease in growth correlated with the damage to, and recovery of, the Na+-dependent amino acid transport system. However, the sensitivity to heat of both growth and Na+-dependent amino acid transport appears to differ in Molt-4 which is somewhat more sensitive to hyperthermia (T-cell line) vs RPMI-1788 (B-cell line). In the case of Molt-4, the rate of growth is decreased for about 60-80 hr after cells are exposed for 1 hr at 43 degrees C; whereas increases in cell number in the RPMI 1788 is observed within 40 hr after the heat treatment. The differences observed in cell growth and transport in these two lymphoid cell lines are attributed to the manner in which heat affects (i) the transport parameters in Molt-4 vs RPMI 1788 (i.e., the Michaelis-Menten constants Km and Vmax) and (ii) the putative plasma membrane sulfhydryl protein(s) which modulates Na+-dependent amino acid transport.