Endocrinology, Vol 123, 1642-1651, Copyright © 1988 by Endocrine Society

ARTICLES

[3H]dexamethasone binding to plasma membrane-enriched fractions from liver of nonadrenalectomized rats

FW Quelle, RV Smith, CA Hrycyna, TD Kaliban, JA Crooks and JM O'Brien
Department of Chemistry and Biochemistry, Middlebury College, Vermont 05753.

Using liver from nonadrenalectomized adult male rats, binding sites for [3H]dexamethasone in particulate fractions are demonstrated. The binding is thermolabile, saturable, and specific for glucocorticoid. The apparent dissociation constant (Kdapp) for [3H]dexamethasone (0.48 +/- 0.084 microM) is 60-fold greater than that for cytosolic receptor (7.9 +/- 1.5 nM). The Kdapp for [3H]cortisol in particulate fractions is 2.5-fold lower than for [3H]dexamethasone (Kdapp = 0.18 microM). The binding capacities for particulate and cytosolic glucocorticoid-binding sites also differ significantly, with particulate sites at least 9.1- fold more concentrated than cytosolic sites in liver tissue. Particulate sites are determined in Percoll density gradients to have a density of 1.039 g/cc. Saturable [3H]dexamethasone radioactivity coelutes from these gradients with the plasma membrane marker enzyme 5'- nucleotidase. Adrenalectomy causes the complete loss of particulate binding sites by 6 days postadrenalectomy; however, these sites can be regenerated to two thirds of the nonadrenalectomy level by 20-30 days postadrenalectomy.

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