Coexistence of two types of Ca(2+)-activated K+ channels in rat renal arterioles. Am J Physiol 1996 Jan;270(1 Pt 2):F69-81
Date
01/01/1996Pubmed ID
8769824DOI
10.1152/ajprenal.1996.270.1.F69Scopus ID
2-s2.0-0030062899 (requires institutional sign-in at Scopus site) 90 CitationsAbstract
Single-channel K+ currents were characterized in vascular smooth muscle cells freshly isolated from preglomerular arterioles (15-40 microns OD) of the rat. Under conditions of symmetrical K+ (145 mM), two types of single-channel K+ currents with unitary slope conductances of 68 +/- 2.6 and 251 +/- 4.9 pS were recorded from excised inside-out membrane patches. The open state probability (NPo) of these two types of K+ channels was voltage sensitive and the channels were highly selective for K+ over Na+. Elevation of intracellular calcium concentration ([Ca2+]i) from 0.1 to 0.5 microM on the cytoplasmic face of inside-out patches increased the frequency of opening and the NPo of both the 68-pS and the 251-pS K+ channels. Application of ATP (0.1-1 mM) to the internal surface of inside-out patches had no effect on the activities of both channel types. Internally applied Ba2+ (1 mM) blocked both of these channels. Externally applied tetraethylammonium (0.1-0.3 mM) or charybdotoxin (50 nM) blocked both the 68-pS and the 251-pS K+ channels. Externally applied apamin (50 nM), however, selectively blocked the 68-pS K+ channel but had no effect on the frequency of opening of the 251-pS K+ channel. Apamin also reduced macroscopic K+ current recorded from voltage-clamped rat renal arteriolar muscle cells by 25-30%. These results indicate the coexistence of two types of Ca(2+)-activated K+ channels in the membranes of vascular smooth muscle cell isolated from renal preglomerular arterioles of the rat that differ in unitary conductances and pharmacological properties.
Author List
Gebremedhin D, Kaldunski M, Jacobs ER, Harder DR, Roman RJMESH terms used to index this publication - Major topics in bold
AnimalsApamin
Arterioles
Barium
Calcium
Charybdotoxin
Electric Conductivity
Ions
Muscle, Smooth, Vascular
Patch-Clamp Techniques
Potassium Channels
Rats
Renal Circulation
Tetraethylammonium
Tetraethylammonium Compounds
