Endothelins activate Ca(2+)-gated K(+) channels via endothelin B receptors in CD-1 mouse erythrocytes.
Cell dehydration mediated by Ca(2+)-activated K(+) channels plays an important role in the pathogenesis of sickle cell disease. CD-1 mouse erythrocytes possess a Ca(2+)-activated K(+) channel (Gardos channel) with maximal velocity (V(max)) of 0.154 +/- 0.02 mmol. l cells(-1). min(-1) and an affinity constant (K(0.5)) for Ca(2+) of 286 +/- 83 nM in the presence of A-23187. Cells pretreated with 500 nM endothelin-1 (ET-1) increased their V(max) by 88 +/- 9% (n = 8) and decreased their K(0.5) for Ca(2+) to 139 +/- 63 nM (P < 0.05; n = 4). Activation of the Gardos channel resulted in an EC(50) of 75 +/- 20 nM for ET-1 and 374 +/- 97 nM for ET-3. Analysis of the affinity of unlabeled ET-1 for its receptor showed two classes of binding sites with apparent dissociation constants of 167 +/- 51 and 785 +/- 143 nM and with capacity of binding sites of 298 +/- 38 and 1,568 +/- 211 sites/cell, respectively. The Gardos channel was activated by the endothelin B (ET(B)) receptor agonist IRL 1620 and inhibited by BQ-788, demonstrating the involvement of ET(B) receptors. Calphostin C inhibited 73% of ET-1-induced Gardos activation and 84% of the ET-1-induced membrane protein kinase C activity. Thus endothelins regulate erythrocyte Gardos channels via ET(B) receptors and a calphostin-sensitive mechanism.
Rivera
A
A
Department of Laboratory Medicine Bader 7, The Children's Hospital, Boston, Massachusetts 02115, USA. rivera_a@a1.tch.harvard.edu
Rotter
M A
MA
Brugnara
C
C
D000818:Animals; D002118:Calcium / Q000502:physiology*; D018946:Chemokine CCL5 / Q000494:pharmacology; D019332:Endothelin-1 / Q000378:metabolism; D016232:Endothelins / Q000494:pharmacology / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism*; D007378:Interleukins / Q000494:pharmacology; D015640:Ion Channel Gating / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009281:Naphthalenes / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000502:physiology
D018946:Chemokine CCL5; D019332:Endothelin-1; D016232:Endothelins; D004791:Enzyme Inhibitors; D007378:Interleukins; D009281:Naphthalenes; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D011493:Protein Kinase C; C058819:calphostin C; D002118:Calcium