The spontaneous and evoked release of spermine from rat brain in vitro.
1 The efflux of previously accumulated [3H]-spermine from brain slices was measured using a continuous perfusion system. The spontaneous efflux was biphasic, consisting of an initial rapid efflux followed by a much slower release. 2 The slices were depolarized by the addition to the medium of high potassium concentrations, ouabain or veratrine. 3 At concentrations greater than 30 mM, potassium evoked a striking increase in the release of [3H]-spermine. Following uptake in the presence of 5.7 x 10(-9)M [3H]-spermine, K+-evoked release was dependent on the presence of calcium ions. Release of spermine after uptake at 5.6 x 10(-8)M or 5.0 x 10(-7)M was not calcium-dependent. 4 The calcium-dependent, K+-stimulated release of spermine was inhibited in the presence of diphenylhydantoin (5 x 10(-5)M) or ruthenium red (10(-5)M). 5 Following uptake of 5.7 x 10(-9)M [3H]-spermine in a sodium-free medium, the calcium-dependent, K+-stimulated release was significantly inhibited. 5 Ouabain (10(-4)M) caused a large but calcium-independent increase in the efflux of [3H]-spermine. 7 Veratrine-induced release was less substantial but was increased in a calcium-free medium. Release evoked by veratrine was abolished in the absence of sodium. 8 These results are discussed with respect to a possible 'neurotransmitter' or 'neuromodulator' role for spermine.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D066298:In Vitro Techniques; D010042:Ouabain / Q000494:pharmacology; D010672:Phenytoin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012430:Ruthenium Red / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013096:Spermine / Q000378:metabolism*; D014316:Tritium; D014702:Veratrine / Q000494:pharmacology
D014316:Tritium; D012430:Ruthenium Red; D013096:Spermine; D010042:Ouabain; D010672:Phenytoin; D012964:Sodium; D014702:Veratrine; D011188:Potassium; D002118:Calcium