[ACTH receptors].
Corticotropin (ACTH) has two main actions in mammalian adrenal cortex: acute stimulation of glucocorticoids secretion and trophic effect which allow the expression of genes encoding for the steroidogenic enzymes. The ACTH membrane bound receptor was one of the first to be demonstrated by direct binding of labeled hormone to subcellular preparations of the adrenal cortex. However, detection and characterization of physiological relevance to ACTH receptors has been difficult, because of the low biological activity of the labeled ACTH. Introduction of a bulky iodine atom into Tyr2 and the oxidation of Met4 appear to contribute most to the loss of activity. These difficulties were overcome recently by using an [125I]-ACTH labeled only in Tyr23, which retains full biological activity. Using this labeled hormone, physiologically relevant ACTH receptors, with high affinity (KD congruent to 10-10M) and low capacity (congruent to 2000 sites/cell) have been characterized in several mammals. A second site of low affinity (KD congruent to 10(-7M) and high capacity, has been found in some studies but the significance of this second site is unknown since it cannot be related to any physiological response of adrenal cells to ACTH. In contrast with the loss of receptors and desensitization of target cells caused by most polypeptide hormones, ACTH seems to regulate positively its own receptors and the cAMP response. The molecular weight of the ACTH receptor appears to be between 83 and 100 KD.(ABSTRACT TRUNCATED AT 250 WORDS)
Saez
J M
JM
INSERM U. 307, Hôpital Debrousse, Lyon.
Begeot
M
M
Durand
P
P
D000262:Adenylyl Cyclases / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000502:physiology; D006801:Humans; D051379:Mice; D051381:Rats; D011979:Receptors, Pituitary Hormone / Q000378:metabolism* / Q000493:pharmacokinetics
D011979:Receptors, Pituitary Hormone; D000324:Adrenocorticotropic Hormone; D000242:Cyclic AMP; D000262:Adenylyl Cyclases
Récepteurs de l'ACTH.