The K channel blocker, tetraethylammonium, displaces beta-endorphin and naloxone from T-cell binding sites.

Beta-endorphin and naloxone bind to Jurkat cell membrane preparations and can mutually displace each other from membrane binding sites. Tetraethylammonium ion, a potassium channel blocker, competitively displaces beta-endorphin and naloxone from membrane binding sites. Mitogen stimulated calcium ion flux is inhibited by tetraethyl ammonium and this inhibition is relieved by naloxone.

Beta-endorphin modulates calcium channel activity in human neutrophils.

10(-6) M n-formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated Ca2+ flux in human neutrophils is characterized by a profile composed of two peaks of different amplitude and breadth. beta-Endorphin inhibited the magnitude and modulated the kinetics of the second peak in a manner which was dose-dependent and could reflect either negative cooperativity or heterogeneity of binding sites. The second peak arises from calcium channel activity since in the presence of nifedipine or EGTA it was not evident while the first peak was reduced about 24%.

Beta-endorphin's modulation of lymphocyte proliferation is dose, donor, and time dependent.

We find that beta-endorphin (Bend) can have, positive, negative, or neutral dose-dependent effects on the mitogen-stimulated proliferation of human peripheral blood lymphocytes. The distribution of positive, negative, or neutral responses was nonrandom. In studies carried out over a year, we show that an individual's mitogen-stimulated lymphocyte proliferative response to Bend can change with time.

Beta-endorphin modulates T-cell intracellular calcium flux and c-myc expression via a potassium channel.

To characterize the effect of beta-endorphin on T-lymphocyte activation, we examined its influence on membrane currents, intracellular calcium flux, and c-myc mRNA levels during mitogenic stimulation of Jurkat cells. While beta-endorphin weakly enhanced voltage-activated K+ currents of Jurkat cells by itself, it suppressed these currents in the presence of mitogen. Naloxone, by itself, also enhanced K+ current amplitude, but in the presence of mitogen partially reversed the suppressive effect of beta-endorphin.

Quin-2 and fura-2 measure calcium differently.

Several fluorescent probes have been used in the past to monitor and to measure intracellular calcium and calcium fluxes. The most widely used of these probes are those developed by Tsien. We address the markedly different values obtained when comparing Quin-2 (the original probe) with Fura-2 (a second-generation probe).