Role of tyrosine kinase and protein kinase C in the steroidogenic actions of angiotensin II, alpha-melanocyte-stimulating hormone and corticotropin in the rat adrenal cortex.
The role of protein kinases in the steroidogenic actions of alpha-melanocyte-stimulating hormone (alpha-MSH), angiotensin II (AngII) and corticotropin (ACTH) in the rat adrenal zona glomerulosa was examined. Ro31-8220, a potent selective inhibitor of protein kinase C (PKC), inhibited both AngII- and alpha-MSH-stimulated aldosterone secretion but had no effect on aldosterone secretion in response to ACTH. The effect of Ro31-8220 on PKC activity was measured in subcellular fractions. Basal PKC activity was higher in cytosol than in membrane or nuclear fractions. Incubation of the zona glomerulosa with either alpha-MSH or AngII resulted in significant increases in PKC activity in the nuclear and cytosolic fractions and decreases in the membrane fraction. These effects were all inhibited by Ro31-8220. ACTH caused a significant increase in nuclear PKC activity only, and this was inhibited by Ro31-8220 without any significant effect on the steroidogenic response to ACTH, suggesting that PKC translocation in response to ACTH may be involved in another aspect of adrenal cellular function. Tyrosine phosphorylation has not previously been considered to be an important component of the response of adrenocortical cells to peptide hormones. Both AngII and alpha-MSH were found to activate tyrosine kinase, but ACTH had no effect, observations that have not been previously reported. Tyrphostin 23, a specific antagonist of tyrosine kinases, inhibited aldosterone secretion in response to AngII and alpha-MSH, but not ACTH. These data confirm the importance of PKC in the adrenocortical response to AngII and alpha-MSH, and, furthermore, indicate that tyrosine kinase may play a critical role in the steroidogenic actions of AngII and alpha-MSH in the rat adrenal zona glomerulosa.
Department of Biochemistry, Faculty of Medical Sciences, Queen Mary and Westfield College, London, U.K.
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S
Kapas
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Purbrick
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JP
Hinson
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000450:Aldosterone / Q000378:metabolism*; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000032:analysis; D002396:Catechols / Q000494:pharmacology; D002451:Cell Compartmentation; D005260:Female; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008297:Male; D009570:Nitriles / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions; D020032:Tyrphostins; D015384:Zona Glomerulosa / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000521:alpha-MSH / Q000494:pharmacology
D002396:Catechols; D007211:Indoles; D009570:Nitriles; D010455:Peptides; D020032:Tyrphostins; D000804:Angiotensin II; D000450:Aldosterone; D000521:alpha-MSH; D000324:Adrenocorticotropic Hormone; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; C060641:tyrphostin A23; D002118:Calcium; C064758:Ro 31-8220