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. 1994 Sep;113(1):171–178. doi: 10.1111/j.1476-5381.1994.tb16190.x

Effects of protein kinase C activators upon the late stages of the ACTH secretory pathway of AtT-20 cells.

B W McFerran 1, S B Guild 1
PMCID: PMC1510056  PMID: 7812608

Abstract

1. The mouse AtT-20/D16-16 anterior pituitary tumour cell line was used as a model system for the study of phorbol 12-myristate 13-acetate (PMA)-mediated enhancement of calcium-evoked adrenocorticotrophin (ACTH) secretion. 2. PMA stimulated ACTH secretion from intact cells in a concentration-dependent manner. Other phorbol esters; phorbol 12,13-dibutyrate (PDBu) and phorbol 12,13-didecanoate (PDD) and diacylglycerol analogues; 1-oleoyl-2-acetyl-sn-glycerol (OAG) and 1,2-dioctanoyl-sn-glycerol (DOG) also stimulated ACTH release from intact AtT-20 cells. This would suggest that activation of protein kinase C (PKC) stimulates ACTH secretion from AtT-20 cells. 3. Calcium stimulated ACTH secretion from electrically-permeabilized cells over the concentration-range of 10(-7) M to 10(-5) M. PMA (10(-7) M) enhanced the amount of ACTH secreted at every concentration of calcium investigated. The PKC inhibitor, chelerythrine (10(-5) M) blocked the PMA (10(-7) M)-evoked enhancement of calcium (10(-5) M)-stimulated ACTH secretion but did not alter significantly the calcium (10(-5) M)-evoked secretion itself. This suggests that PKC modulates the secretory response to increases in intracellular calcium but does not mediate the effects of calcium. 4. Guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S, 10(-5) M) stimulated ACTH secretion from permeabilized cells in the absence of calcium and was additive with calcium-evoked ACTH secretion up to a maximum value which could be achieved by calcium acting alone. This suggests that a GTP-binding protein mediates the secretory response to increases in the intracellular calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

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Selected References

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