1995 Fiscal Year Final Research Report Summary
Effects of PACAP on the gene expression of catecholamine synthesizing enzymes.
| Project/Area Number |
06671000
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
内分泌・代謝学
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| Research Institution | University of Tsukuba |
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Principal Investigator |
ISOBE Kazumasa Institute of Clinical Medicine University of Tsukuba, Lectuer, 臨床医学系, 講師 (10151440)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAI Toshiaki Institute of Clinical Medicine University of Tsukuba, Professor, 臨床医学系, 教授 (30049192)
NOMURA Fumio Institute of Clinical Medicine University of Tsukuba, Assistant Professor, 臨床医学系, 助教授 (80164739)
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| Project Period (FY) |
1994 – 1995
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| Keywords | PACAP / mRNA / catecholamine synthesis / adrenal medulla / tyrosine hydroxylase / dopamine-beta-hydroxylase |
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| Research Abstract |
Pituitary adenylate cyclase-activating polypeptide (PACAP), a potent stimulant for catecholamine secretion, stimulated catecholamine production in cultured porcine adrenal medullary chromaffin cells. PACAP induced dose-and time-dependent increases in mRNAs for the catecholamine synthesizing enzymes, tyrosine hydroxylase (TH) and dopamine b-hydroxylase (DBH), with maximal 6-and 4-fold increases occuring at 8 to 16h, respectively. The half-maximally and maximally effective PACAP concentrations for stimulation of TH and DBH gene expression were 0.5 and 0.3 nM,respectively. The TH-protein level also showed an increase over the unstimulated basal level at 16 to 24h in PACAP-stimulated cells.
We previously demonstrated that PACAP activates both phospholipase C and adenylate cyclase in adrenal medullary cells. Addition of forskolin alone induced increases in mRNA expression of both TH and DBH.The phosphodiesterase inhibior 3-isobutyl-1-methylxanthine potentiated the induction of TH and DBH mRNA by PACAP.Addition of the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) also caused increases in TH and DBH mRNA levels. In protein kinase C-downregulated cells pretrearted with PMA for 24h, the stimulatory effect of PACAP on TH and DBH gene expression was diminished. These results suggest that cAMP and protein kinase C mediated the PACAP-induced TH and DBH gene expression. Removal of extracellular Ca2+with EGTA enhanced the PACAP-induced increases in both cellular cAMP and mRNA levels of TH and DBH mRNAs.
In conclusion, the present study indicates that PACAP coordinately up-regulates the gene expression of both TH and DBH by activating the cAMP and protein kinase C signaling pathway, leading to stimulation of catecholamine synthesis, while Ca2+negatively regulates TH and DBH gene expression in adrenal medullaru cells.
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