Membrane potential of rat adipocytes: effect of phospholipase C, concanavalin A, and adenosine.
The change in transmembrane potential of rat adipocytes was measured using the fluorescent probe 3,3'-diethylthiadicarbocyanine iodide, diS-C2-(5). The method was calibrated by altering the potassium ion concentration while keeping the sum of potassium and sodium ions at a constant concentration of 153 mM (Bailey et al: Bioelectrochem. Bioenergetics 21:333-42, 1989). Two insulin-mimetic agents, phospholipase C from Clostridium perfringens and concanavalin A, induced a dose dependent hyperpolarization of rat epididymal adipocytes, like insulin. Removal of endogenous adenosine with adenosine deaminase or adenosine receptor blockade with isobutylmethylxanthine following the initiation of insulin-induced hyperpolarization resulted in depolarization. These same agents induced hyperpolarization of -6 to -8 mV when added without insulin. The replacement of adenosine with its analogue, N6-phenylisopropyladenosine, plus insulin depolarized the cells toward the transmembrane potential established by insulin, -2.0 mV. These studies suggest that adenosine receptor occupancy is required to maintain insulin-induced hyperpolarization.
Kiechle
F L
FL
Department of Clinical Pathology, William Beaumont Hospital, Royal Oak, MI 48073-6769.
Bailey
F
F
Hill
N
N
Malinski
T
T
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology*; D000243:Adenosine Deaminase / Q000494:pharmacology; D000273:Adipose Tissue / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D003208:Concanavalin A / Q000494:pharmacology*; D004225:Dithiazanine; D005456:Fluorescent Dyes; D007328:Insulin / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials; D010660:Phenylisopropyladenosine / Q000494:pharmacology; D058915:Purinergic P1 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D010738:Type C Phospholipases / Q000494:pharmacology*
D005456:Fluorescent Dyes; D007328:Insulin; D058915:Purinergic P1 Receptor Antagonists; D003208:Concanavalin A; D010660:Phenylisopropyladenosine; D004225:Dithiazanine; D010738:Type C Phospholipases; D000243:Adenosine Deaminase; D000241:Adenosine; D015056:1-Methyl-3-isobutylxanthine