Calcium release from separate receptor‐specific intracellular stores induced by histamine and ATP in a hamster cell lineden Hartog, A., Hoiting, B., Molleman, A., van den akker, J., Duin, M. & Nelemans, A., Aug-1992, In : Journal of physiology-London. 454, p. 591-607 17 p.
Research output: Contribution to journal › Article › Academic › peer-review
1. The specificity of intracellular Ca2+ stores to Ca2+-mobilizing agonists was studied in DDT1 MF-2 vas deferens cells of the Syrian hamster.
2. Application of histamine (100-mu-M or ATP (100-mu-m) to the DDT, 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 Ca2+-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 H-1 histaminoceptor antagonist mepyramine (10-mu-m) and the responses evoked by ATP were blocked by the P2 purinoceptor antagonist suramin (300-mu-M).
5. A second internal Ca2+ response could only be evoked under Ca2+-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-mu-m) of the agonist to the cells under Ca2+-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-mu-M) with a transient Ca2+ response if successively applied at a maximal effective concentration (100-mu-M) under Ca2+-free conditions.
8. Simultaneous stimulation of H-1 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.
9. A transient increase in cytoplasmic Ca2+ was evoked by ATP or histamine (100-mu-M) in the presence of both external Ca2+ (1.2 mM) and La3+ (50 mM, 10 min). A second addition of the same agonist failed to evoke a Ca2+ response if preceded by a recovery period (15 min) in the presence of Ca2+ and La3+. Using the other agent as second agonist resulted again in a transient rise in internal Ca2+.
10. Subsequent application of the agonists to the cell population under Ca2+-free conditions. after removing the first agonist in between both responses, resulted in a rise in internal Ca2+ and Ins(1,4.5)P3. Hyperpolarization was observed in single cells following this experimental protocol.
11. The results imply that stimulation of H-1 histaminoceptors or P2 purinoceptors on DDT1 MF-2 vas deferens cells activate a process resulting in calcium release from separate receptor-specific intracellular stores.
|Number of pages||17|
|Journal||Journal of physiology-London|
|Publication status||Published - Aug-1992|
- SMOOTH-MUSCLE CELLS, INOSITOL PHOSPHATE FORMATION, RABBIT EAR ARTERY, PIG TAENIA CECI, GUINEA-PIG, CYTOPLASMIC CALCIUM, ADENOSINE-TRIPHOSPHATE, POTASSIUM CHANNELS, MEMBRANE CURRENTS, INTERNAL CALCIUM