Abstract：
:Tyrosine hydroxylase (TH) is the rate-limiting enzyme in the biosynthesis of catecholamines. In a previous report we found that intracerebroventricular administration of nitric oxide (NO) generator sodium nitroprusside (SNP) to conscious male rats inhibited dose-dependently the TH activity of the median eminence (ME). In the present study we have tested the in vitro effects of SNP on TH activity, its possible mediator and action mechanism. Exposure of the ME TH to SNP (50, 100 and 500 microM) caused concentration-dependent inhibition of its enzyme activity. Addition of; reduced hemoglobin Hb (10 microM), a NO scavenger, superoxide dismutase SOD (1000 units/ml), a superoxide scavenger enzyme, or uric acid UA (300 microM), a peroxynitrite scavenger, did not affect the enzyme activity by themselves, but prevented the inhibitory effect of SNP 500 microM. However, the presence of methylene blue MB (100 microM), a guanylyl cyclase inhibitor, did not alter either basal enzyme activity or the inhibitory action of SNP 500 microM. These results suggest that this action of SNP on TH of the ME would be mediated by peroxynitrite generated by the reaction of NO with superoxide.
journal_name
Life Scijournal_title
Life sciencesauthors
Abreu P,Llorente E,Sánchez JJ,González MCdoi
10.1016/s0024-3205(00)00782-7subject
Has Abstractpub_date
2000-09-08 00:00:00pages
1941-6issue
16eissn
0024-3205issn
1879-0631pii
S0024320500007827journal_volume
67pub_type
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