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Rat mast cells permeabilized with ATP secrete histamine in response to calcium ions buffered in the micromolar range.

1981; Wiley; Volume: 317; Issue: 1 Linguagem: Inglês

10.1113/jphysiol.1981.sp013828

1469-7793

Jonathan P. Bennett, Shamshad Cockcroft, Bastien D. Gomperts,

Neuropeptides and Animal Physiology

1. Rat mast cells with ATP (0.5‐4 micro M) in the absence of divalent cations (so that almost all the ATP is present as ATP4‐) became permeable to normally impermeant aqueous solutes, added extracellularly. These include the stable complexes Co HEDTA and Ca EDTA, and 6‐carboxyfluorescein but not inulin. At 4 micro M‐ATP4‐ the space accessible to Ca EDTA is 89% of that occupied by 3H2O. 2. The kinetics of solute entry are regulated by the concentration of ATP4‐. 3. Ca2+, buffered in the range 1‐10 micro M with HEDTA, causes histamine secretion from mast cells that have been rendered permeable with ATP4‐. The extent of secretion increases as the concentration of ATP4‐ is raised from 3 to 5 micro M. With extracellular Ca2+ present as physiological (millimolar) concentrations, the effect of increasing ATP4‐ through this range is to inhibit secretion. 4. The rates of histamine secretion and of 32P‐metabolite leakage from 32P‐prelabelled cells in the presence of micromolar concentrations of Ca2+, were compared. The kinetics of both processes are regulated by the concentration of ATP4‐, but not Ca2+.