Calcium release from separate receptor-specific intracellular stores induced by histamine and ATP in a hamster cell line.
1. The specificity of intracellular Ca2+ stores to Ca(2+)-mobilizing agonists was studied in DDT1 MF-2 vas deferens cells of the Syrian hamster. 2. Application of histamine (100 microM) or ATP (100 microM) to the DDT1 MF-2 cells caused an initial increase of intracellular Ca2+ followed by a lower phase as measured by using Indo-1 as fluorescent probe at 22 degrees C. The basal Ca2+ level (146 nM) was enhanced to 309 nM by histamine and to 379 nM by ATP. 3. A transient rise in intracellular Ca2+ lasting for about 2 min was measured in the presence of histamine or ATP in the absence of extracellular Ca2+. The basal Ca2+ level (78 nM) was increased to 128 nM by histamine and to 145 nM by ATP. 4. A transient hyperpolarization was elicited in single cells as measured with microelectrodes by both agonists under Ca(2+)-free conditions with a similar time course as the change in internal Ca2+. The hyperpolarization observed in the presence of histamine amounted to 23 mV and 31 mV with ATP. The histamine-induced responses were abolished by the H1 histaminoceptor antagonist mepyramine (10 microM) and the responses evoked by ATP were blocked by the P2 purinoceptor antagonist suramin (300 microM). 5. A second internal Ca2+ response could only be evoked under Ca(2+)-free conditions by applying a higher agonist concentration or after replenishing the intracellular stores with Ca2+ from the extracellular space. 6. A second addition of an optimal concentration (100 microM) of the agonist to the cells under Ca(2+)-free conditions did not evoke mobilization of internal Ca2+ or hyperpolarization, but resulted in a rise of the cellular inositol (1,4,5)-trisphosphate content (Ins(1,4,5)P3) as determined by a radioligand binding assay. 7. The cells responded to both agonists (100 microM) with a transient Ca2+ response if successively applied at a maximal effective concentration (100 microM) under Ca(2+)-free conditions. 8. Simultaneous stimulation of H1 histaminoceptors and P2 purinoceptors resulted in the absence of external Ca2+ in an additional increase in internal Ca2+ represented by the amplitude and area of the response and in an increased response area of the hyperpolarization.(ABSTRACT TRUNCATED AT 400 WORDS)
Den Hertog
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A
Department of Pharmacology/Clinical Pharmacology, University of Groningen, The Netherlands.
Hoiting
B
B
Molleman
A
A
Van den Akker
J
J
Duin
M
M
Nelemans
A
A
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D004594:Electrophysiology; D006632:Histamine / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials; D008647:Mesocricetus; D011969:Receptors, Histamine H1 / Q000502:physiology; D011983:Receptors, Purinergic / Q000502:physiology; D014649:Vas Deferens / Q000378:metabolism
D011969:Receptors, Histamine H1; D011983:Receptors, Purinergic; D006632:Histamine; D000255:Adenosine Triphosphate; D002118:Calcium