ONTOGENY OF THE RAT HEPATIC RECEPTOR FOR "2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN AND ITS ENDOCRINE INDEPENDENCE

Abstract

The ontogeny of the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) [a potent inducer of the aryl hydrocarbon hydroxylase system involved in carcinogenesis] receptor was studied in Sprague-Dawley rats by quantitation of the receptor in liverl cytosol using isoelectric focusing in polyacrylamide gel. No differences by sex in the receptor concentration were seen at any of the ages studied. Newborn, 21 day old and 42 day old rats contained significantly more receptor in the liver cytosol than did 56 day old rats. There was no significant difference in the receptor concentration in liver cytosol from 7 day old rats compared to that from 56 day old rats. The maximum receptor concentration was found in cytosol from 21 day old rats [36.1 .+-. 24.0 (SD) f[femto]mol/mg protein]. Adult rats (56 days old) contained the lowest concentraton of receptor (13.3 .+-. 6.3 fmol/mg protein). The level of TCDD receptor in liver cytosol from adult rats was not significantly changed by orchiectomy, ovariectomy, adrenalectomy or hypophysectomy. The maximum for TCDD receptor concentration at puberty corresponds to the reported maximum for the induction of aryl hydrocarbon hydroxylase activity. No further conclusion can as yet be drawn concerning the regulation of the TCDD receptor.