NDLI: Divalent ion block of inward rectifier current in human capillary endothelial cells and effects on resting membrane potential

Content Provider	PubMed Central
Author	Jow, Flora Numann, Randy
Copyright Year	1998
Abstract	Cultured human capillary endothelial cells (HCEC) contain a large inward rectifier current, I K(IR), that can be abolished by removing external K+ or by adding 50 μm Ba2+. We show that I K(IR) is responsible for maintaining the hyperpolarized potential (−60.6 ± 0.5 mV, n = 83) of HCEC. Blocking I K(IR) with 50 μm Ba2+ shifts the zero current level and depolarizes HCEC by 36.5 ± 1.3 mV (n = 4). Increasing external Ca2+ concentration ([Ca2+]o) from 0.5 to 7 mm reduces the magnitude of I K(IR) by 36.5 ± 2.3 % (n = 5) and depolarizes the cells by 10.33 ± 2.4 mV (n = 3), whereas decreasing [Ca2+]o from 1.8 to 0.5 mm increases the amplitude of I K(IR) by 6.9 ± 1.9 % (n = 4). The relationship between [Ca2+]o and the percentage block of I K(IR) gives a K d value of 5.4 ± 0.6 mm at −120 mV. I K(IR) is also blocked by other divalent ions, with Ba2+ >> Sr2+ > Mg2+ > Mn2+= Ca2+, and the block of peak current at −120 mV being 85.3 ± 3.2 % (n = 5) for 50 μm Ba2+, 62.9 ± 2.2 % (n = 5) for 5 mm Sr2+, 40.7 ± 2.5 % (n = 9) for 5 mm Mg2+, 33.4 ± 2.1 % (n = 5) for 5 mm Mn2+ and 32.9 ± 2.1 % (n = 5) for 5 mm Ca2+. The voltage dependence of Sr2+ block of peak I K(IR) occurred with a K d value of 1.0 ± 0.09 mm for −140 mV, 1.9 ± 0.16 mm for −130 mV, 3.1 ± 0.28 mm for −120 mV, 4.6 ± 0.34 mm for −110 mV and 6.4 ± 0.5 mm for −100 mV (n = 5), with a calculated electrical distance (δ) of 0.44 from the outside.
Related Links	http://dx.doi.org/10.1111/j.1469-7793.1998.119bf.x
Ending Page	128
Page Count	10
Starting Page	119
File Format	PDF
ISSN	00223751
e-ISSN	14697793
Journal	The Journal of Physiology
Issue Number	Pt 1
Volume Number	512
Language	English
Publisher	Blackwell Science Inc
Publisher Date	1998-10-01
Access Restriction	Open
Rights Holder	Blackwell Science Inc
Subject Keyword	Physiology Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Physiology Sports Science

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