title: Potassium-channel blockers inhibit inositol trisphosphate-induced calcium release in the microsomal fractions isolated from the rat brain.
abstract: The ionic mechanism of inositol trisphosphate (InsP3)-induced Ca2+ release was investigated in microsomes (microsomal fractions) isolated from rat brain. InsP3 stimulated Ca2+ release from microsomes incubated in media containing 100 mM-KCl. The InsP3-induced Ca2+ release was insensitive to a variety of Ca2+-channel blockers; however, the K+-channel blockers tetraethylammonium chloride (TEA; 1 mM) and 9-tetraethylammonium chloride (9-TEA; 1 mM) blocked InsP3-induced Ca2+ release. Moreover, addition of InsP3 increased 86Rb+ influx into the microsomes. The influx of 86Rb+ also was sensitive to TEA and 9-TEA. The above results suggest that InsP3-induced Ca2+ release requires an opposite flow of K+ ions, and modulation of K+ channels by TEA and 9-TEA may underlie the inhibition of InsP3-induced Ca2+ release from brain microsomes by these agents.
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects*; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D013403:Sugar Phosphates / Q000494:pharmacology*
chemical_list: D007295:Inositol Phosphates; D007473:Ion Channels; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D012413:Rubidium; D011188:Potassium; D002118:Calcium