Summary
-
1.
Rat hearts were perfused with 50–2000 μM 3H-(−)-noradrenaline in the presence of 14C-sorbitol (to measure the extracellular distribution of the amine) and of 100 μM cocaine (to inhibit neuronal uptake). Initial rates of removal of noradrenaline were determined. Extraneuronal uptake determined in this way consisted of two components: a saturable and a non-saturable one.
-
2.
When monoamine oxidase (MAO) was inhibited, the kinetic constants for saturable extraneuronal uptake of noradrenaline were: K m 60 μM, V max 50 nmoles · g−1 · min−1. U-0521, an inhibitor of catechol-O-methyl transferase (COMT) acted like a competitive inhibitor of extraneuronal uptake: the K m increased, V max remained unaffected.
-
3.
In separate experiments either MAO or COMT was intact. Rat hearts were perfused with various concentrations of 3H-(−)-noradrenaline until the metabolites appeared at a constant rate in the venous effluent. These steady-state rates of metabolite formation were used to determine the kinetic parameters of the metabolizing systems.
-
4.
O-methylation of noradrenaline in the intact heart was a saturable process and obeyed Michaelis-Menten kinetics; it had very low K m (1.7 μM) and V max (1.2 nmoles · g−1 · min−1).
-
5.
Also the deamination of noradrenaline by the perfused heart was a saturable process, but K m and V max were considerably higher than for O-methylation (140 μM and 25 nmoles · g−1 · min−1, respectively).
-
6.
It is concluded that “extraneuronal uptake and subsequent metabolism” of noradrenaline represents a site of loss that is highly effective at very low substrate concentrations (i.e., below the K m of the two metabolizing systems).
Similar content being viewed by others
References
Bausher, L. P., Sears, M. L.: Potentiation of the effects of topical epinephrine on pupil and intraocular pressure in the sympathetically denervated rabbit eye by a catechol-O-methyl transferase inhibitor. Invest Opthalmol. 15, 854–857 (1976)
Bönisch, H.: Further studies of the extraneuronal uptake and metabolism of isoprenaline in the perfused heart. Naunyn-Schmiedeberg's Arch. Pharmacol. (in press, 1978)
Bönisch, H., Trendelenburg, U.: Extraneuronal removal, accumulation and O-methylation of isoprenaline, in the perfused heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 283, 191–218 (1974)
Bönisch, H., Uhlig, W., Trendelenburg, U.: Analysis of the compartments involved in the extraneuronal storage and metabolism of isoprenaline in the perfused heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 283, 223–244 (1974)
Callingham B. A., Burgen, A. S. V.: The uptake of isoprenaline and noradrenaline by the perfused rat heart. Mol. Pharmacol. 2, 37–42 (1966)
Farnebo, L.-O.: Histochemical studies on the uptake of noradrenaline in the perfused rat heart. Br. J. Pharmacol. 34, 227P-228P (1968)
Fiebig, E. R., Trendelenburg, U.: The kinetic constants of the extraneuronal uptake and metabolism of 3H-(-)-noradrenaline in the isolated perfused rat heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 297, R 48 (1977)
Fiebig, E. R., Trendelenburg, U.: The neuronal, and extraneuronal uptake and metabolism of 3H-(-)-noradrenaline in the perfused rat heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 303, 21–35 (1978)
Gillespie, J. S., Muir, T. C.: Species and tissue variation in extraneuronal and neuronal accumulation of noradrenaline. J. Physiol. (Lond.) 206, 591–604 (1970)
Gillespie, J. S., Preuner, J.: Influence of iproniazid and 3′,4′-dihydroxy-2-methyl-propiophenone (U-0521) on uptake and metabolism of norepinephrine by rabbit colon. Naunyn-Schmiedeberg's Arch. Pharmacol. 293, R 3 (1976)
Graefe, K.-H., Trendelenburg, U.: The effect of hydrocortisone on the sensitivity of the isolated nictitating membrane to catecholamines. Relationship to extraneuronal uptake and metabolism. Naunyn-Schmiedeberg's Arch. Pharmacol. 286, 1–48 (1974)
Graefe, K.-H., Stefano, F.J.E., Langer, S.Z.: Preferential metabolism of (-)-3H-norepinephrine through, the deaminated glycol in the rat vas deferens. Biochem. Pharmacol. 22, 1147–1160 (1973)
Graefe, K.-H., Bönisch, H., Keller, B.: Saturation kinetics of the adrenergic neurone uptake system in the perfused rabbit heart. A new method for determination of initial rates of uptake. Naunyn-Schmiedeberg's Arch. 302, 263–273 (1978)
Guimaraes, S., Azevedo, I., Cardoso, W., Oliveira, M. C.: Relation between the amount of smooth muscle of venous tissue and the degree of supersensitivity to isoprenaline caused by inhibition of catechol-O-methyl transferase. Naunyn-Schmiedeberg's Arch. Pharmacol 286, 401–412 (1974)
Iversen, L. L.: The uptake of catecholamines at high perfusion concentrations in the rat isolated heart: A novel catechol amine uptake process. Br. J. Pharmacol. 25, 18–31 (1965)
Iversen, L. L.: The uptake and storage of noradrenaline in sympathetic nerves. Cambridge: Cambridge University Press 1967
Kaumann, A. J.: Adrenergic receptors in heart muscle: relations among factors influencing the sensitivity of the cat papillary muscle to catecholamines. J. Pharmacol. Exp. Ther. 173, 383–398 (1970)
Kaumann, A. J.: Potentiation of the effects of isoprenaline and noradrenaline by hydrocortisone in cat heart muscle. Naunyn-Schmiedeberg's Arch. Pharmacol. 273, 134–153 (1972)
Lightman, S. L., Iversen, L. L.: The role of uptake2 in the extraneuronal metabolism of catecholamines in the isolated rat heart. Br. J. Pharmacol. 37, 638–649 (1969)
Trendelenburg, U., Höhn, D., Graefe, K.-H., Pluchino, S.: The influence of block of catechol-O-methyl transferase on the sensitivity of isolated organs to catecholamines. Naunyn-Schmiedeberg's Arch. Pharmak. 271, 59–92 (1971)
Uhlig, W., Bönisch, H., Trendelenburg, U.: The O-methylation of extraneuronally stored isoprenaline in the perfused heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 283, 245–261 (1974)
Wilkinson, G. N.: Statistical estimations in enzyme kinetics. Biochem. J. 80 324–332 (1961)
Author information
Authors and Affiliations
Additional information
This study was supported by the Deutsche Forschungsgemeinschaft
Rights and permissions
About this article
Cite this article
Fiebig, E.R., Trendelenburg, U. The kinetic constants for the extraneuronal uptake and metabolism of 3H-(−)-Noradrenaline in the perfused rat heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 303, 37–45 (1978). https://doi.org/10.1007/BF00496183
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00496183