title: Steroidogenic activity of highly potent melanotropic peptides in the adrenal cortex of the rat.
abstract: Highly purified ACTH and MSH peptides were studied in isolated rat glomerulosa and inner zone cells and their activity compared with that in an Anolis melanophore assay. While both ACTH1-39 and ACTH1-24 were almost equally potent steroidogenic peptides in the two cell types (ED50 between 1 and 4 X 10(-12) M), alpha-MSH displayed only weak steroidogenic activity. Although it was a full agonist, it was about 10(4)-fold less potent in both capsular and inner zone cells. beta-MSH (porcine) was even 10-fold less active in capsular cells than alpha-MSH, and in inner zone cells it was a partial agonist. Highly potent melanotropic peptides, such as (Nle4, D-Phe7)-alpha-MSH or cyclic (Cys4, Cys10)-alpha-MSH were either inactive or exhibited only a very slight partial steroidogenic activity in both cell types. Comparison of the activity profile of additional compounds, such as des-acetyl alpha-MSH, (Tyr(I)2)-alpha-MSH, (Trp(For)9)-alpha-MSH or (Nva12)-alpha-MSH, in the adrenocortical and pigment cell assays led to the conclusion that alpha-MSH does not exert its steroidogenic effect through a typical melanocyte-type of MSH receptor, but rather through a low affinity-type of ACTH receptor.
mesh_terms: D000302:Adrenal Cortex / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D010860:Pigments, Biological / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D018043:Receptors, Corticotropin; D011979:Receptors, Pituitary Hormone / Q000378:metabolism
chemical_list: D010860:Pigments, Biological; D018043:Receptors, Corticotropin; D011979:Receptors, Pituitary Hormone; C029446:MSH receptor; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones