Alamethicin channel permeation by Ca2+, Mn2+ and Ni2+ in bovine chromaffin cells

FEBS Letters

Garcia-Sancho, J.¹  López, M.G.²  Fonteriz, R.I.¹  Garcia, A.G.² 

[1] Departamento de Fisiologia y Bioquimica, Facultad de Medicina, Universidad de Valladolid, 47005-Valladolid, Spain;Departamento de Farmacologia y Terapèutica, Facultad de Medicina, Universidad Autonòma de Madrid, Arzobispo, Morcillo, 4, 28029-Madrid, Spain

关键词: Alamethicin;    Calcium signal;    Manganese;    Nickel;    Furu-2;    Chromaffin cell;   

DOI  :  10.1016/0014-5793(91)80560-P

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Alamethicin causes a concentration-dependent increase of (Ca²⁺), in suspensions of bovine adrenal chromaffin cells loaded with fura-2. The basal levels of Ca²⁺ (234 ± 37 nM; n=4) increased to a maximum of 2347±791 nM (n=3) with 100 μg/ml alamethicin. In the presence of 1 nM Ca²⁺ the increase reached a plateau within about 2–5 s. This increase was due to Ca²⁺ entry into chromaffin cells, since in the absence of Ca²⁺ alamethicin did not modify [Ca²⁺]. This contrasts with ionomycin (1 μM) which produced a Ca²⁺ transient even in the absence of Ca²⁺, Mn²⁺ ions also entered chromaffin cells in the presence of alamethicin, as measured by the quenching of fura-2-fluorescence following excitation at 360 nm. Resting chromaffin cells had a measurable permeability to Mn²⁺ which was drastically increased by cell depolarization by K⁺ (50 nM) addition. This suggests that Mn²⁺ is able to permeate voltage-dependent Ca²⁺ channels. Ni²⁺ uptake into either resting of K⁺-stimulated chromaffin cells was undetectable, but addition of alamethicin induced rapid uptake of this cation. The alamethicin-induced entry of Ni²⁺ was decreased by 50 mM K⁺. Overall, the results are compatible with the formation by alamethicin of ion channels in chromaffin cell plasma membranes.

【 授权许可】

Unknown