Stress-induced decrement in the plasticity of the physical properties of chick brain membranes

GARCIA DA; MARIN RH,; PERILLO MA,

MOLECULAR MEMBRANE BIOLOGY

TAYLOR & FRANCIS LTD

Año: 2002 vol. 19 p. 221 - 230

0968-7688

The molecular basis underlying the stress-induced increment in the density of central benzodiazepine receptor (CBR) from chick forebrain, observed previously at 4oC, was studied from a biophysical perspective. The thermal dependence of [3H]FNZ binding to CBR and the supramolecular organization were studied in forebrain membranes from chicks submitted to partial water immersion. The equilibrium dissociation constants increased with temperature in membrane from both control (CON) and stressed (STR) chicks. The heat capacity values in CON samples (DCp, CON) were significantly less negative than DCp STR. Changes in DH and DS between 4 and 37°C were greater in STR compared to CON; however, the binding was exothermic and driven by enthalpy in both conditions. At 4°C, the receptor density (Bmax) was higher in STR compared to CON. Such difference was lost irreversibly upon temperature elevation, possibly due to the hysteresis between the heating and cooling behaviour of Bmax, CON and the constancy in Bmax, STR The fluorescence anisotropy of diphenylhexatriene was higher in CON samples with respect to STR bellow 10°C. A temperature-induced increment in protein intrinsic-fluorescence was observed only in CON, and was quenched by acrylamide more easily at  4°C than at 25°C. A higher microviscosity at 4oC in CNT favoured more external localizations of integral proteins; at higher temperatures tryptophan residues moved to hydrophobic membrane-regions. Changes in the Membrane-organization towards more fluid states favoured the accessibility of BZD to CBR, expressed by the higher values of Bmax found in STR samples at low temperatures with respect to CON samples .