Characterization of regulatory volume decrease in the THP-1 and HL-60 human myelocytic cell lines.
Exposure to hypotonic stress produces a transient increase in cell volume followed by a regulatory volume decrease (RVD) in both THP-1 and HL-60 cells. In contrast, cells exposed to hypotonic stress in a high K/low Na Hanks' solution not only failed to volume regulate, but displayed a secondary swelling. Thus, while an outward K gradient was required for RVD, the secondary swelling indicated that hypotonic stress increased permeability in the absence of a negative membrane potential. The K channel blocker quinine (1-4 mM) blocked RVD in both cell types. Gramicidin's ability to overcome the quinine block of RVD indicated that RVD is mediated by a quinine-sensitive cation transport mechanism that is independent of the swelling-induced anion transport mechanism. Barium (1-4 mM), another K channel blocker, slowed the rate of RVD, while 4-aminopyridine, charybdotoxin, tetraethylammonium chloride, tetrabutylammonium chloride, and gadolinium had no effect on RVD. Furthermore, RVD was not mediated by calcium-activated conductances, since it occurred normally in Ca-free medium, in medium containing cadmium, and in BAPTA-loaded cells. Gramicidin produced little or no volume change in isotonic medium, suggesting that basal C1 permeability of both THP-1 and HL-60 cells is low. However, swelling induced an anion efflux pathway that is permeable to both chloride and bromide, but is impermeable to methanesulfonate and glutamate. The anion channel blocker 3,5-diiodosalicylic acid (DISA) antagonized RVD in both cell types. In conclusion, RVD in THP-1 and HL-60 cells is mediated by independent anion and cation transport mechanisms that involve both a DISA-sensitive anion pathway and a quinine-inhibitable K efflux pathway, neither of which requires increases in intracellular calcium to be activated.
Gallin
E K
EK
Department of Physiology, Armed Forces Radiobiology Research Institute, Bethesda, Maryland 20889-5603.
Mason
T M
TM
Moran
A
A
D000838:Anions / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability; D002470:Cell Survival; D016257:Fura-2; D006096:Gramicidin / Q000494:pharmacology; D006706:Homeostasis; D006801:Humans; D007038:Hypotonic Solutions; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011803:Quinine / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000502:physiology*
D000838:Anions; D007038:Hypotonic Solutions; D015221:Potassium Channels; D006096:Gramicidin; D011803:Quinine; D002118:Calcium; D016257:Fura-2