Functional evidence for the regulation of cytosolic Ca2+ activity via V1A-receptors and beta-adrenoceptors in rat CCD.
In freshly isolated rat CCD segments, the effects of arginine vasopressin (AVP), oxytocin (OT), adrenaline (Ad), and their specific receptor agonists and antagonists on the intracellular Ca2+ activity ([Ca2+]i) were measured using the Ca2+ sensitive dye Fura-2 as fluorescence indicator. We observed that AVP, the V1-receptor agonist [Phe2Orn8] vasotocin ([Phe2]OVT), and OT increased [Ca2+]i biphasically. AVP (n = 9) and OT (n = 8) induced increases in [Ca2+]i were completely blocked by the V1A-receptor antagonist d(CH2)5Tyr(Me)2AVP. However, neither the V2-receptor agonist [Val4-D-Arg8]AVP (100 nM, n = 5), nor the OT-receptor agonist [Thr4,Gly7]OT (100 nM, n = 5) nor forskolin (1 microM, n = 4 and 10 microM, n = 5) did significantly change [Ca2+]i. Ad and the beta-adrenoceptor agonist isoproterenol (ISO) increased [Ca2+]i, which was not mimicked by the alpha 2-adrenoceptor agonist clonidine (1 microM, n = 10) or the alpha 1-adrenoceptor agonist phenylephrine (1 microM, n = 5). The beta-adrenoceptor antagonist propranolol (1 microM) completely blocked this Ad (1 microM, n = 4) induced [Ca2+]i increase. Insulin (INS 10 nM, n = 8), endothelin (ET 1 microM, n = 6), and angiotensin II (Ang II 1 pM to 10 nM; each n = 4) had no significant effect on [Ca2+]i. Considering the present results we propose a V1A-receptor and beta-adrenoceptor dependent modulation of [Ca2+]i in rat CCD.
Ankorina-Stark
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Medizinische Poliklinik, Westfälische Wilhelms-Universität, Münster, Germany.
Haxelmans
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Schlatter
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D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D046508:Culture Techniques; D003600:Cytosol / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology; D007672:Kidney Cortex / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D017483:Receptors, Vasopressin / Q000819:agonists / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D004791:Enzyme Inhibitors; D011943:Receptors, Adrenergic, beta; D017483:Receptors, Vasopressin; D014667:Vasopressins; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D007545:Isoproterenol; D002118:Calcium; D004837:Epinephrine