Is reverse triiodothyronine a physiological nonactive competitor for the action of triiodothyronine upon the electrical properties of GH3 cells?
The electrical properties of GH3 cells, a transformed line from the rat pituitary, were studied with a current-clamp technique in the presence of triiodothyronine (T3) and reverse triiodothyronine (rT3) and compared with the known effects of T3. rT3 had an effect only in a concentration of 1 microM; action potentials were suppressed, and changes in the slope conductance were similar to those seen in response to T3. Membrane resistance RI decreased, and the resting membrane potential VM hyperpolarized. The action of rT3 is a 1,000 times less potent than that of T3 and is unlikely to have a physiological significance. When a cell was beforehand superfused with rT3 (10 nM), the effect of T3 was prevented even in a concentration of 10 nM. The specificity of T3, the prevention of the effect of T3 by rT3, and the small dose needed suggest a binding site for T3. The short latency of its action implies an extranuclear binding site, probably in or near the plasma membrane of the GH3 cell.
du Pont
J S
JS
Department of Experimental Zoology, Biologisch Centrum Gebouw II, University of Amsterdam, The Netherlands.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D004553:Electric Conductivity; D004594:Electrophysiology; D008564:Membrane Potentials / Q000187:drug effects; D010902:Pituitary Gland / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D014284:Triiodothyronine / Q000494:pharmacology*; D014285:Triiodothyronine, Reverse / Q000494:pharmacology*
D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse