Inhibitory effects of proopiomelanocortin on cortical and medullary activity in the calf adrenal.
The effects of the infusion of ACTH1-24 and proopiomelanocortin on the denervated adrenal gland have been investigated in conscious 3-6 weeks-old calves by means of the adrenal-clamp technique. To prevent variation in the release of endogenous ACTH the pituitary stalk was cauterized during preparatory surgery. ACTH1-24 (5 ng/min per kg, i.v.) increased the output of cortisol from the adrenal by about 500 ng/min per kg body weight and this effect was rapidly reduced by simultaneous infusion of ovine proopiomelanocortin at 5 ng/min per kg. Release of met5-enkephalin and leu-enkephalin from the adrenal was reduced by ACTH1-24 (P less than 0.05) and this effect was enhanced significantly by additional infusion of proopiomelanocortin (P less than 0.02). However met5-enkephalin represented less than one-third of the met-enkephalin containing peptide released and the output of this pool was unaffected by infusion of ACTH. Proopiomelanocortin had no effect on met5-enkephalin production nor that of the total pool of met5-enkephalin containing peptides. It is concluded that ACTH reduced the quantity of pro-enkephalin processed to met5-enkephalin.
Jones
C T
CT
Physiological Laboratory, University of Cambridge, UK.
Edwards
A V
AV
Tindell
D
D
D000302:Adrenal Cortex / Q000187:drug effects* / Q000378:metabolism; D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D002417:Cattle; D003366:Cosyntropin / Q000494:pharmacology; D004743:Enkephalin, Leucine / Q000097:blood / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000097:blood / Q000378:metabolism; D004745:Enkephalins / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism*; D007016:Hypophysectomy; D011333:Pro-Opiomelanocortin / Q000494:pharmacology*; D011498:Protein Precursors / Q000378:metabolism*
D004745:Enkephalins; D011498:Protein Precursors; C029992:proenkephalin; D003366:Cosyntropin; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone