P2-purinergic stimulation of iodide efflux in FRTL-5 rat thyroid cells involves parallel activation of PLC and PLA2.
Extracellular ATP increases inositol phosphates, cytosolic Ca2+ concentration ([Ca2+]i), arachidonic acid (AA) release, and iodide efflux in FRTL-5 cells. To examine the sequence of events in P2-purinergic receptor activation by ATP, a phospholipase C (PLC) inhibitor (U-73122) and a phospholipase A2 (PLA2) inhibitor (U-26384), as well as 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'- tetraacetic acid (BAPTA) and downregulation of protein kinase C (PKC) were used. ATP increased inositol trisphosphate (IP3), [Ca2+]i, AA release, and 125I efflux dose dependently. U-73122 inhibited the IP3 and calcium increase but not AA; U-26384 prevented AA release but not the increase in calcium. Both agents inhibited iodide efflux. BAPTA prevented any ATP-induced increase in [Ca2+]i without affecting AA release or 125I efflux. PKC downregulation had no effect on ATP-stimulated AA release, but reduced 125I efflux. We conclude that ATP-induced iodide efflux involves parallel, not sequential, activation of PLC and PLA2. No increase in [Ca2+]i or PKC activity is required for PLA2 activation. In contrast, an increase in 125I efflux depends on PKC and PLA2 activities, but not an increase in [Ca2+]i.
Smallridge
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RC
Department of Clinical Physiology, Walter Reed Army Institute of Research, Washington, District of Columbia 20307-5100.
Gist
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ID
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D004963:Estrenes / Q000494:pharmacology; D007454:Iodides / Q000378:metabolism*; D009994:Osmolar Concentration; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D011493:Protein Kinase C / Q000378:metabolism; D011687:Purines / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D015290:Second Messenger Systems; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004963:Estrenes; D007454:Iodides; D011687:Purines; D011760:Pyrrolidinones; C057358:U 26384; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D016718:Arachidonic Acid; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium