Endothelins activate Ca(2+)-gated K(+) channels via endothelin B receptors in CD-1 mouse erythrocytes

Area of Science:

• Physiology
• Molecular Biology
• Pharmacology

Background:

• Cell dehydration in sickle cell disease is linked to calcium-activated potassium channels.
• The Gardos channel in mouse erythrocytes is a key target for understanding these processes.

Purpose of the Study:

• To investigate the role of endothelins in regulating erythrocyte Gardos channels.
• To elucidate the specific receptors and signaling pathways involved in endothelin-mediated Gardos channel activation.

Main Methods:

• Utilized patch-clamp electrophysiology to measure Gardos channel activity (Vmax, K0.5).
• Employed radioligand binding assays to characterize endothelin receptor interactions.
• Investigated receptor subtype involvement using specific agonists and antagonists (IRL 1620, BQ-788).
• Assessed the role of protein kinase C using calphostin C.

Main Results:

• Endothelin-1 (ET-1) significantly increased Gardos channel Vmax and decreased its Ca(2+) affinity.
• ET-1 and ET-3 demonstrated dose-dependent activation of the Gardos channel.
• High-affinity binding sites for ET-1 were identified on erythrocytes.
• The endothelin B (ET(B)) receptor was implicated in channel activation, as shown by agonist/antagonist studies.
• Calphostin C inhibited ET-1-induced Gardos channel activation and protein kinase C activity.

Conclusions:

• Endothelins regulate erythrocyte Gardos channels through ET(B) receptors.
• A calphostin-sensitive pathway, likely involving protein kinase C, mediates this regulation.
• Findings provide insights into the molecular mechanisms underlying cell dehydration in sickle cell disease.