Purinergic control of intercellular communication between Hensen's cells of the guinea-pig cochlea.
1. Hensen's cells in the isolated cochlea were stimulated by extracellular adenosine 5'-triphosphate (ATP) applied to their endolymphatic surface while changes in membrane current and intracellular calcium concentration ([Ca2+]i) were measured simultaneously. The response consisted of (i) an initial rapid inward current accompanied by elevation of the [Ca2+]i, (ii) a more slowly rising inward current accompanied by a rise of the [Ca2+]i and (iii) a slowly developing reduction of input conductance. 2. The slower responses were maintained in the absence of extracellular Ca2+. Similar responses were produced by increasing the [Ca2+]i via UV flash photolysis of intracellular D-myo-inositol 1,4,5-trisphosphate, P4(5)-(1-(2-nitrophenyl)ethyl) ester (caged InsP3) loaded at pipette concentrations of 8-16 microM. 3. The slow inward current, reversing around 0 mV, was blocked by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). 4. Bath application of U-73122 (1 microM), a phospholipase C inhibitor, eliminated the slow Ca2+-release component of the response to ATP. It is proposed that the effects of ATP are mediated by the co-activation of ionotropic P2X and metabotropic P2Y receptors. 5. Immunohistochemistry using light and electron microscopy revealed that inositol 1,4,5-trisphosphate (InsP3) receptors delineate a network within the cells. 6. The coupling ratio (CR) between cell pairs measured in dual patch-clamp recordings was 0.356 +/- 0.024. The coupling reversibly decreased to 51 % of the control within 2 min of applying 100 microM ATP. Flash photolysis of 32 microM intracellular caged InsP3 and 1 mM caged Ca2+ reduced CR to 42 and 62 % of the control, respectively. 7. We propose that endolymphatic ATP via P2X and P2Y receptors can control intercellular communication amongst Hensen's cells by reducing gap junction conductance in a Ca2+- and InsP3-dependent manner.
Settore di Biofisica e Istituto Nazionale di Fisica della Materia, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34014 Trieste, Italy.
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Lagostena
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Ashmore
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Kachar
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Mammano
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002450:Cell Communication / Q000502:physiology*; D003051:Cochlea / Q000166:cytology* / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D006168:Guinea Pigs; D007150:Immunohistochemistry; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D010782:Photolysis; D011687:Purines / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013997:Time Factors; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D014466:Ultraviolet Rays
D004791:Enzyme Inhibitors; D011687:Purines; C029273:P(3)-1-(2-nitro)phenylethyladenosine 5'-triphosphate; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D002118:Calcium