Summary
Triamterene, which is structurally similar to the natural cofactor of tyrosine hydroxylase, (6R)-l-erythro-5,6,7,8-tetrahydrobiopterin, inhibited tyrosine hydroxylase in rat adrenal gland homogenates and was found to be a competitive inhibitor of the synthetic cofactor 6,7-dimethyl-5,6,7,8-tetrahydrobiopterin. When triamterene (30 mg/kg i.p.) was administered to rats, a significant decrease in the adrenal, whole brain and kidney enzyme activities was observed after 90 min; if the drug was given orally, the diuretic affected only adrenal tyrosine hydroxylase. In both cases the drug decreased potassium excretion to 1/5 of control values and increased the excretion of sodium. Catecholamine levels in atria, kidneys, adrenal glands and whole brain were not affected in acute experiments. Chronic treatment (triamterene 30 mg/kg p.o. twice daily during 4 days) inhibited tyrosine hydroxylase and decreased catecholamine levels in the kidneys. Low potassium excretion was observed throughout the 4 days of treatment. In these chronic experiments the inhibition of the adrenal enzyme seen in acute treatments was not observed. This recovery cannot be explained by increase in the adrenal biopterin levels. It could be mediated by an induction of the adrenal tyrosine hydroxylase.
Similar content being viewed by others
References
Bhatnagar RK, Moore KE (1971) Effects of electrical stimulation, α-methyl-p-tyrosine and desmethylimipramine on the norepinephrine contents of neuronal cell bodies and terminals. J Pharmacol Exp Ther 178:450–463
Dayton PG, Pruitt AW, McNay JL, Steinhorst J (1972) Studies with triamterene, a substituted pteridine. Unusual brain to plasma ratio in mammals. Neuropharmacology 11:435–446
Fukushima T, Nixon JC (1980) Analysis of reduced forms of biopterin in biological tissues and fluids. Anal Biochem 102:176–188
Gutman Y, Segal J (1972) Effect of calcium, potassium and sodium on adrenal tyrosine hydroxylase activity in vitro. Biochem Pharmacol 21:2664–2666
Gutman Y, Segal J (1973) Effect of calcium, potassium and sodium on tyrosine hydroxylase activity in different regions of the rat brain. Biochem Pharmacol 22:865–868
Lassen JB, Nielsen OE (1963) Investigations into the diuretic effect and elimination of triamterene. Acta Pharmacol Toxicol 20:309–316
Laverty R, Taylor KM (1968) The fluorimetric assay of catecholamines and related compounds: improvements and extension to the hydroxyindole technique. Anal Biochem 22:269–279
Lloyd T, Weiner N (1971) Isolation and characterization of a tyrosine hydroxylase cofactor from bovine adrenal medulla. Mol Pharmacol 7:569–580
Nagatsu T (1981) Biopterin cofactor and regulation of monoamine-synthesizing mono-oxygenase. Trends Pharmacol Sci 2 (10): 276–279
Pruitt AW, Winkel JS, Dayton PG (1977) Variations in the fate of triamterene. Clin Pharmacol Ther 21:610–619
Waymire JC, Bjur R, Weiner N (1971) Assay of tyrosine hydroxylase by couple decarboxylation of DOPA from [1-14C]-l-tyrosine. Anal Biochem 43:588–600
Weiner N, Cloutier G, Bjur R, Pfeffer RI (1972) Modification of norepinephrine synthesis in intact tissue by drugs and during short term adrenergic nerve stimulation. Pharmacol Rev 24:203–221
Wiebelhaus VD, Weinstock J, Maass AR, Brennan FT, Sosnowski G, Larsen T (1965) The diuretic and natriuretic activity of triamterene and several related pteridines in the rat. J Pharmacol Exp Ther 149:397–403
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Steinberg, P., Rubio, M.C. Effect of triamterene on tyrosine hydroxylase activity. Naunyn-Schmiedeberg's Arch. Pharmacol. 327, 119–123 (1984). https://doi.org/10.1007/BF00500905
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00500905