REGULATORY ACTION OF THYROID HORMONES ON HEPATOCYTE CELL MEMBRANE POTENTIAL CENERATION

The aim of the research is to verify the thyroid hormones activity on the membrane potential generation in rat liver cell coltures and to estimate the mitochondrial role in this process. The isolated hepatocytes were obtained from 60 days old male rats, Wistar strain, according to the method of Seglen (Seglen P.O., Methods Cell Biol., 1976, 13, 29). Membrane potential was determined by the spectrofluorometric evaluation of propidium iodide label transport across plasma membrane by means of the Stopped flow spectrofluorometer of Hi-Tech Scientific (United Kingdom). The mitochondrial role was estimated through either a permeant compound specific for the H+ channels ( CCCP: carbonylcyanide m-chlorophenylhydrazone) or a respiratory chain inhibitor (rhotenone). The thyroid hormones LT3 and LT4 at the final concentration of 2,4 and 6 nM were used according to M. J. Obregon (Obregon M.J. et al., Endocrinology 1981, 109:908-913). Borh LT3 and LT4 increase membrane potential at their addition, once upon a time, to isolated cells,(32 ,4+3,5% as measured by fluorescence).ln the in presence of rhotenone and CCCP the mitochondria fail to support the potential generation and this partial inhibition is more evident with LT3 (6.3+1.7% with Rhotenone and 16.3+1,8% with CCCP) than with LT4 (24.1+2.1%with Rhotenone and 20,6+1.8% with CCCP),Our data confirm the contribution of the mitochondrial fraction to the cell membrane potential generation under the control of thyroid hormones.