Elsevier

Biochemical Pharmacology

Volume 22, Issue 23, 1 December 1973, Pages 2947-2960
Biochemical Pharmacology

Effects of 2-mercaptoethylguanidine and other compounds on norepinephrine synthesis by adrenal medullary granules

https://doi.org/10.1016/0006-2952(73)90181-0Get rights and content

Abstract

The effects of 2-mercaptoethylguanidine and other compounds on dopamine uptake and norepinephrine synthesis by adrenal medullary granules were studied. The effects of these materials on crude dopamine-β-hydroxylase were also tested. A microanalytical technique was developed which allows the use of the natural precursor, dopamine, in studies of uptake and synthesis by adrenal medullary granules. The conversion of dopamine to norepinephrine by dopamine-β-hydroxylase was also studied with this technique. Catecholamines were assayed as their dansyl (5-dimethylaminonaphthalene-1-sulfonyl) derivatives, thereby increasing greatly the resolution and sensitivity of detection. The effects of 2-mercaptoethylguanidine and reserpine on dopamine uptake and norepinephrine synthesis by medullary granules were compared. Reserpine inhibited norepinephrine synthesis indirectly through inhibition of dopamine uptake. 2-Mercaptoethylguanidine, on the other hand, depressed norepinephrine synthesis in intact granules by a direct inhibitory effect on dopamine-β-hydroxylase rather than on the uptake mechanism. 2-Mercaptoethylguanidine increased the rate of norepinephrine synthesis by crude dopamine-β-hydroxylase in the presence of added Cu2+ and inhibited norepinephrine synthesis in the absence of added Cu2+. The nature of the latter effect was resolved by demonstrating the formation of a Cu-2-mercaptoethyl-guanidine complex in pure solutions. Since dopamine-β-hydroxylase is a Cu-containing enzyme, the mechanism of the 2-mercaptoethylguanidine inhibition of dopamine-β-hydroxylase appears to be through the binding of enzymic Cu.

References (22)

  • N. Kirshner

    J. biol. Chem.

    (1962)
  • M. Goldstein et al.

    Biochem. Pharmac.

    (1965)
  • E.J. Diliberto et al.

    Analyt. Biochem.

    (1969)
  • G.A. Bray

    Analyt. Biochem.

    (1960)
  • S. Friedman et al.

    J. biol. Chem.

    (1965)
  • D.S. Duch et al.

    Biochem. Pharmac.

    (1968)
  • T. Nagatsu et al.

    Biochim. biophys. Acta

    (1967)
  • F. Belpaire et al.

    Biochem. Pharmac.

    (1970)
  • A. Carlsson et al.

    Medna exp.

    (1962)
  • A. Carlsson et al.

    Acta physiol. scand.

    (1963)
  • S. Spector et al.

    J. Pharmac. exp. Ther.

    (1965)
  • Cited by (3)

    This work was supported in part by USPHS grants 1-P11-GM-15190 and 5-T01-GM00032.

    Present address: Department of Pharmacology, Medical School, University of Pennsylvania, Philadelphia, Pa. 19104.

    View full text