Early plasma-membrane-potential changes during stimulation of lymphocytes by concanavalin A.
1. We have monitored the plasma-membrane potential of lymphocytes by measuring the accumulation of the lipophilic cation methyltriphenylphosphonium (TPMP+) in the presence of the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP). 2. The mitogen concanavalin A causes a decrease in TPMP+ accumulation by pig lymphocytes corresponding to a 3 mV depolarization with 2 1/2 min. Concanavalin A does not alter 86Rb+ uptake in the first 30 min. 3. In contrast concanavalin A increased TPMP+ accumulation and the rate of Rb+ uptake in mouse thymocytes. This is consistent with a previous proposal that the mitogen induces a hyperpolarization of mouse thymocytes as a result of stimulation of a Ca2+-dependent K+ channel. 4. Studies with the calcium ionophore A23187 and quinine (an inhibitor of the Ca2+-dependent K+ channel) suggest that the channel is partially closed in mouse resting thymocytes but is almost fully active in pig resting cells. Thus concanavalin A hyperpolarizes mouse thymocytes by activating the Ca2+-dependent K+ channel but cannot do so in pig lymphocytes because the channel is already maximally activated. 5. The 3mV depolarization of pig cells cannot be explained by a decrease in electrogenic K+ permeability.
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D003208:Concanavalin A / Q000494:pharmacology*; D066298:In Vitro Techniques; D008213:Lymphocyte Activation / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D009861:Onium Compounds; D011803:Quinine / Q000494:pharmacology; D012413:Rubidium / Q000378:metabolism; D013552:Swine; D013816:Thermodynamics; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D014320:Triphenylmethyl Compounds / Q000378:metabolism
D009861:Onium Compounds; D014320:Triphenylmethyl Compounds; D003208:Concanavalin A; C011561:triphenylmethylphosphonium; D000001:Calcimycin; D011803:Quinine; D012413:Rubidium