beta(3)-adrenergic stimulation and insulin inhibition of non-selective cation channels in white adipocytes of the rat

Citation
E. Ringer et al., beta(3)-adrenergic stimulation and insulin inhibition of non-selective cation channels in white adipocytes of the rat, BBA-BIOMEMB, 1463(2), 2000, pp. 241-253
Citations number
40
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
ISSN journal
00052736 → ACNP
Volume
1463
Issue
2
Year of publication
2000
Pages
241 - 253
Database
ISI
SICI code
0005-2736(20000215)1463:2<241:BSAIIO>2.0.ZU;2-0
Abstract
Single-channel currents were recorded from the plasma membrane of white adi pocytes of 6-8-week-old male Sprague-Dawley rats. In outside-out patches th igh K+, no Ca2+ in pipette), a voltage-dependent K-channel (delayed rectifi er) with a single-channel conductance (gamma) of 16 pS (24 degrees C) in mo dified Ringer's was active at a density of 0.5/mu m(2). It was blocked by T EA (IC50 = 1.5 mM). A Ca2+-activated non-selective cation channel (NSC-chan nel) appeared at a mean density of 1/mu m(2) in inside-out patches ([Ca2+]( i) = 1.2 mM). gamma was 28 pS (24 degrees C). The NSC showed weak voltage d ependence and was blocked by mefenamic acid and by internal ATP. In the cel l-attached mode spontaneous activity could be blocked reversibly by 100 nM insulin. Noradrenaline (NA, 100 nM) induced a flickering activity of the NS C-channels. Isoproterenol (100 nM) caused activity of the NSC-channel as we ll. After 1 mu M propranolol even 1 mu M NA did not induce any activity. Th e alpha-antagonist phentolamine had no effect on isoproterenol- or on NA-in duced currents. The beta(3)-agonists BRL 37344 and BRL 35135A induced activ ity of the NSC-channel at 100 nM as well. We conclude that white adipocytes express ion channels which are comparable to those in brown adipocytes and that beta-receptor activation opens NSC-channels thus allowing for Na+ ent ry into white adipocytes. (C) 2000 Elsevier Science B.V. All rights reserve d.