Diogo Nóbrega Catelas1, Maria Paula Serrão1,2, Patricio Soares-Da-Silva1,2. 1. Department of Biomedicine, Unit of Pharmacology and Therapeutics, Faculty Medicine, University of Porto, Porto, Portugal. 2. MedInUP - Center for Drug Discovery and Innovative Medicines, University of Porto, Porto, Portugal.
Abstract
Background and Objective: Evaluate the activity of dopamine-β-hydroxylase (DβH) as well as the effect of the DβH inhibitor nepicastat upon enzyme activity and levels of dopamine (DA) and norepinephrine (NE) in the rat left ventricle, kidney, and adrenal glands. Methods: DβH assay consisted of the enzymatic hydroxylation of tyramine into octopamine, and DA and NE tissues levels were quantified by HPLC-ED. Results: Nepicastat (30 mg/kg, p.o.) reduced DβH activity by 93% and 80% in the adrenals at 4 h and 8 h postdrug administration, accompanied by significant reductions in NE and epinephrine tissue levels and an increase in DA levels and of DA/NE tissue ratios, with similar findings for NE, DA and of DA/NE tissue ratios in left ventricle and kidney. DβH activity in the left ventricle and kidney showed a high degree of variability, which does not allow corroboration of the effects of nepicastat upon catecholamine tissue levels. Conclusion: The assay of DβH activity in heart and kidney lacks the necessary robustness, but DβH activity in the adrenals appears to be an appropriate marker. However, the effect size upon DA/NE tissue ratios (an indirect measure of DβH activity) as induced by nepicastat was very similar in sympathetically innervated tissues, left ventricle and kidney, and the adrenal medulla.
Background and Objective: Evaluate the activity of dopamine-β-hydroxylase (DβH) as well as the effect of the DβH inhibitor nepicastat upon enzyme activity and levels of dopamine (DA) and norepinephrine (NE) in the rat left ventricle, kidney, and adrenal glands. Methods: DβH assay consisted of the enzymatic hydroxylation of tyramine into octopamine, and DA and NE tissues levels were quantified by HPLC-ED. Results:Nepicastat (30 mg/kg, p.o.) reduced DβH activity by 93% and 80% in the adrenals at 4 h and 8 h postdrug administration, accompanied by significant reductions in NE and epinephrine tissue levels and an increase in DA levels and of DA/NE tissue ratios, with similar findings for NE, DA and of DA/NE tissue ratios in left ventricle and kidney. DβH activity in the left ventricle and kidney showed a high degree of variability, which does not allow corroboration of the effects of nepicastat upon catecholamine tissue levels. Conclusion: The assay of DβH activity in heart and kidney lacks the necessary robustness, but DβH activity in the adrenals appears to be an appropriate marker. However, the effect size upon DA/NE tissue ratios (an indirect measure of DβH activity) as induced by nepicastat was very similar in sympathetically innervated tissues, left ventricle and kidney, and the adrenal medulla.
Entities:
Keywords:
Dopamine β-hydroxylase; catecholamines; nepicastat; rat; sympathetic nervous system
Authors: Frank Faltraco; Denise Palm; Adriana Uzoni; Lena Borchert; Frederick Simon; Oliver Tucha; Johannes Thome Journal: J Neural Transm (Vienna) Date: 2021-07-18 Impact factor: 3.575