Biophysical properties of Ca2+- and Mg-ATP-activated K+ channels in pulmonary arterial smooth muscle cells isolated from the rat

Sulayma Albarwani, Blair E. Robertson, Piers C.G. Nye, Roland Z. Kozlowski*

*المؤلف المقابل لهذا العمل

نتاج البحث: المساهمة في مجلةمراجعة النظراء

39 اقتباسات (Scopus)

ملخص

A novel class of Ca2+-activated K+ channel, also activated by Mg-ATP, exists in the main pulmonary artery of the rat. In view of the sensitivity of these "KCa,ATP" channels to such charged intermediates it is possible that they may be involved in regulating cellular responses to hypoxia. However, their electrophysiological profile is at present unknown. We have therefore characterised the sensitivity of KCa,ATP channels to voltage, intracellular Ca2+ ([Ca2+]i) and Mg-ATP. They have a conductance of 245 pS in symmetrical K+ and are approximately 20 times more selective for K+ ions than Na+ ions, with a K+ permeability (PK) of 4.6×10-13cm s-1. Ca2+ ions applied to the intracellular membrane surface of KCa,ATP channels causes a marked enhancement of their activity. This activation is probably the result of simultaneous binding of at least two Ca2+ ions, determined using Hill analysis, to the channel or some closely associated protein. This results in a shift of the voltage activation threshold to more hyperpolarized membrane potentials. The activation of KCa,ATP channels by Mg-ATP has an EC50 of approximately 50 μM. Although the EC50 is unaffected by [Ca2+]i, channel activation by Mg-ATP is enhanced by increasing [Ca2+]i. One possible interpretation of these data is that Mg-ATP increases the sensitivity of KCa,ATP channels to Ca2+. It is therefore possible that under hypoxic conditions, where lower levels of Mg-ATP may be encountered, the sensitivity of KCa,ATP channels to Ca2+ and therefore voltage is reduced. This would tend to induce a depolarising influence, which would favour the influx of Ca2+ through voltage-activated Ca2+ channels, ultimately leading to increased vascular tone.

اللغة الأصليةEnglish
الصفحات (من إلى)446-454
عدد الصفحات9
دوريةPflügers Archiv European Journal of Physiology
مستوى الصوت428
رقم الإصدار5-6
المعرِّفات الرقمية للأشياء
حالة النشرPublished - أكتوبر 1994
منشور خارجيًانعم

ASJC Scopus subject areas

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