AJP - Regulatory, Integrative and Comparative Physiology, Vol 235, Issue 3 115-R120, Copyright © 1978 by American Physiological Society
Glucocorticoid receptors in the guinea pig
A. J. Hodgson and J. W. Funder
In cytoplasmic fractions of liver and kidney prepared from adrenalectomized
guinea pigs, tritiated dexamethasone ([3H]DM) is bound with a very low
affinity (Kd 4 degrees C greater than or equal to 2 X 10(-7) M). By
competition studies, the specificity of this binding was shown to be
comparable with that for [3H]DM binding to glucocorticoid receptors in
other species. In addition, cytoplasmic preparations from guinea pig liver
and kidney appear to inhibit the binding of [3H]DM to rat glucocorticoid
receptors under a variety of experimentally determined circumstances. It is
proposed that such inhibitory activity may reflect a system of [3H]DM
sequestration, perhaps by metabolizing enzymes with a high combining power
for glucocorticoids. Both low affinity glucocorticoid receptors and avid
binding to sites of metabolism may represent additive cellular bases for
the apparent corticoresistance of the guinea pig.
