MEMBRANE-POTENTIAL OF RAT ADIPOCYTES - EFFECT OF PHOSPHOLIPASE-C CONCANAVALIN-A, AND ADENOSINE

The change in transmembrane potential of rat adipocytes was measured u sing the fluorescent probe 3,3'-diethylthiadicarbocyanine iodide, diS- C-2-(5). The method was calibrated by altering the potassium ion conce ntration while keeping the sum of potassium and sodium ions at a const ant concentration of 153 mM (Bailey et al: Bioelectrochem. Bioenergeti cs 21:333-42, 1989). Two insulin-mimetic agents, phospholipase C from Clostridium perfringens and concanavalin A, induced a dose dependent h yperpolarization of rat epididymal adipocytes, like insulin. Removal o f endogenous adenosine with adenosine deaminase or adenosine receptor blockade with isobutylmethylxanthine following the initiation of insul in-induced hyperpolarization resulted in depolarization. These same ag ents induced hyperpolarization of -6 to -8 mV when added without insul in. The replacement of adenosine with its analogue, N-6-phenylisopropy ladenosine, plus insulin depolarized the cells toward the transmembran e potential established by insulin, -2.0 mV. These studies suggest tha t adenosine receptor occupancy is required to maintain insulin-induced hyperpolarization.