Electrophysiological characteristics of HT-29 cells from human colon adenocarcinoma

Matter transport across the gastrointestinal barrier is closely related to the membrane properties of the single cells of the epithelium. The aim of this research was to study the electrical properties of an established tumor cell line, the HT-29 cells, an adenocarcinoma of human colon. In confluent cultures the cells, grown in a synthetic medium (RPMI), were impaled with one microelectrode to measure the electrical membrane potential (M.P.) under different experimental conditions. Experiments were performed at room temperature (23 – 25 °C). In normal saline (Hanks) the resting membrane potential mean values (+ SE) in 8 culture dishes ranged from -20.5 ± 1.1 mV (n = 18) to -36.8 ± 1.8 mV (n = 59). The content of K+ in the surrounding medium was changed and the membrane potential recorded after a long exposure (45 - 60 min). The extracellular K+ concentration, [K+]o ranged from 0.44 mM to 43.40 mM. At [K+]o lower than in Hanks solution (5.81 mM) hyperpolarizations were obtained up to 142.6 % of the normal value, when [K+]o = 0.44 mM. Higher hyperpolarizations were measured in cells grown in the presence of cholesterol (100 µg/ml) while at high [K+]o these cells exhibited a lower depolarization than those grown in the absence of cholesterol. The effects of amiloride and ouabain were tested, too. Only after a long exposure, amiloride seemed to hyperpolarize the cellular membrane while ouabain depolarized more rapidly the cells grown in normal conditions than those grown in RPMI plus cholesterol. The observations reported above are just some of the general electrophysiological characteristics of HT-29 cells, because other aspects, such as polarization of plasma membrane, synchronization and heterogeneity of cell population, possibility of dome formation, need further consideration.