Effects of polyhydric and monohydric compounds on the stability of type I receptors for adrenal steroids in brain cytosol.

We have shown previously that unoccupied type I receptors for adrenal steroids in brain cytosol lose their capacity to bind [3H]aldosterone ([3H]ALDO) in a time- and temperature-dependent manner. Based on reports that sugars and polyvalent alcohols are capable of stabilizing a variety of globular proteins, we attempted in the present study to stabilize type I receptors by including polyhydric compounds in our brain cytosol preparations. However, contrary to expectations, adjusting cytosol to a 10% (g/dl) concentration of ethylene glycol, glycerol, erythritol, xylitol, ribitol, or sorbitol failed to stabilize these receptors at 0 degree C and in fact produced a slight reduction in [3H]ALDO binding capacity. The magnitude of this reduction was greater when cytosol was incubated for 2 h at 22 degrees C prior to incubation with [3H]ALDO. In contrast to these results, when brain cytosol was adjusted to a 10% (g/dl) concentration of the monohydric compound, ethanol, a significant increase in [3H]ALDO binding to type I receptors was found. Under identical conditions, methanol and propanol failed to have a significant effect on the binding capacity of these receptors. When cytosol was aged for 2 h at 22 degrees C, all three of these monohydric compounds produced a marked loss in the [3H]ALDO binding capacity of type I receptors. An investigation of various doses of ethanol at 0 degree C on the subsequent binding of [3H]ALDO yielded an inverse U-shaped curve with 10% ethanol producing the highest level of specific binding, as reflected by an increase in maximal binding in Scatchard plots, and 40% ethanol producing a complete loss in type I receptor binding capacity.(ABSTRACT TRUNCATED AT 250 WORDS)