ABSTRACT
Single-channel currents were recorded from the plasma membrane of white adipocytes of 6-8-week-old male Sprague-Dawley rats. In outside-out patches (high K(+), no Ca(2+) in pipette), a voltage-dependent K-channel (delayed rectifier) with a single-channel conductance (gamma) of 16 pS (24 degrees C) in modified Ringer's was active at a density of 0.5/microm(2). It was blocked by TEA (IC(50)=1.5 mM). A Ca(2+)-activated non-selective cation channel (NSC-channel) appeared at a mean density of 1/microm(2) in inside-out patches ([Ca(2+)](i)=1.2 mM). gamma was 28 pS (24 degrees C). The NSC showed weak voltage dependence and was blocked by mefenamic acid and by internal ATP. In the cell-attached mode spontaneous activity could be blocked reversibly by 100 nM insulin. Noradrenaline (NA, 100 nM) induced a flickering activity of the NSC-channels. Isoproterenol (100 nM) caused activity of the NSC-channel as well. After 1 microM propranolol even 1 microM NA did not induce any activity. The alpha-antagonist phentolamine had no effect on isoproterenol- or on NA-induced currents. The beta(3)-agonists BRL 37344 and BRL 35135A induced activity 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(+) entry into white adipocytes.
Subject(s)
Adipocytes/physiology , Adrenergic beta-Agonists/pharmacology , Cell Membrane/physiology , Inulin/pharmacology , Ion Channels/physiology , Potassium Channels, Voltage-Gated , Receptors, Adrenergic, beta/physiology , Tetraethylammonium/pharmacology , Adenosine Triphosphate/pharmacology , Adipose Tissue/cytology , Adipose Tissue/physiology , Animals , Calcium/pharmacology , Cell Membrane/drug effects , Cells, Cultured , Delayed Rectifier Potassium Channels , Ion Channel Gating/drug effects , Ion Channel Gating/physiology , Ion Channels/drug effects , Isoproterenol/pharmacology , Male , Membrane Potentials , Norepinephrine/pharmacology , Patch-Clamp Techniques , Potassium Channel Blockers , Potassium Channels/physiology , Rats , Rats, Sprague-Dawley , Receptors, Adrenergic, beta-3 , Receptors, Purinergic P1/drug effects , Receptors, Purinergic P1/physiologyABSTRACT
Using the mixed cell agglutination reaction (MCAR) in a modification by Ishiyama and Okada (MCAR on adhesive tape) we examined single rootless hairs collected from 65 men, women and children (aged 6 months to 80 years). Correct results gave 57 probes (87%). False-positive and false-negative results mainly occurred at non-secretor donors. The modified method is quickly done, reproducible and does not alter the hair.
