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Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 304, Issue 2, pp 147–155 | Cite as

The determination of the rate constant for the efflux of an amine from efflux curves for amine and metabolite

  • H. Bönisch
  • K. -H. Graefe
  • U. Trendelenburg
Article

Summary

  1. 1.

    Rat hearts were perfused with 0.1 μM 3H-isoprenaline for 10 min in the presence of 10 μM U-0521 to inhibit catechol-O-methyl transferase (COMT) and then washed out with amine-free solution. Analysis of efflux curves revealed a preferential filling of one (compartment III) of the two extraneuronal compartments described by Bönisch et al. (1974). U-0521 inhibited the efflux of isoprenaline from compartment III. Omission of U-0521 from the wash out solution quickly restored COMT activity. It was then possible to determine the rate constant for the efflux (ks) of isoprenaline from rate of efflux and amine content of tissue.

     
  2. 2.

    A procedure is developed which permits the calculation of ks from efflux curves for amine and metabolite without any need for determining the amine content of the tissue. With this procedure, ks can be determined even when there is a “bound fraction” (i.e., a second compartment, the amine content of which does not contribute to the experimentally determined efflux). The procedure is based on the fact that, for a single compartment in which the amine is metabolized and from which there is efflux of amine and metabolite, parallel efflux curves (i.e., plots of log rate of efflux against time) are obtained, if the rate constant for the efflux of the metabolite (kp) is higher than the rate constant for the loss of amine from the compartment (ksystem). The activity of the metabolizing enzyme determines ksystem and the ratio “initial rate of efflux of metabolite/initial rate of efflux of amine” (F0).

     
  3. 3.

    A mathematical model (simulating metabolism in, and efflux of amine and metabolite from a single compartment) was used to determine the distortion of F0 by “ksystem/kP” (when kP limits the efflux of the metabolite). An estimate of ks obtained from F0 and from ksystem agrees well with the estimate of ks obtained directly (see 1, above).

     

Key words

Rate constant for efflux of amine Isoprenaline Simulated efflux curves Extraneuronal mechanism Mathematical model 

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References

  1. Bönisch, H.: Further studies of the extraneuronal uptake and metabolism of isoprenaline in the perfused heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 303, 121–131 (1978)Google Scholar
  2. 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)Google Scholar
  3. Eckert, E., Henseling, M., Gescher, A., Trendelenburg, U.: Stereoselectivity of the distribution of labelled noradrenaline in rabbit aortic strips after inhibition of the noradrenalinemetabolizing enzymes. Naunyn-Schmiedeberg's Arch. Pharmacol. 292, 219–229 (1976a)Google Scholar
  4. Eckert, E., Henseling, M., Trendelenburg, U.: The effect of inhibitors of extraneuronal uptake on the distribution of 3H-(±)-noradrenaline in nerve-free rabbit aortic strips. Naunyn-Schmiedeberg's Arch. Pharmacol. 293, 115–127 (1976b)Google Scholar
  5. 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 (1978a)Google Scholar
  6. 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 (1978b)Google Scholar
  7. Henseling, M., Trendelenburg, U.: Stereoselectivity of the accumulation and metabolism of noradrenaline in rabbit aortic strips. Naunyn-Schmiedeberg's Arch. Pharmacol. 302, 195–206 (1978)Google Scholar
  8. Henseling, M., Eckert, E., Trendelenburg, U.: The distribution of 3H-(±)-noradrenaline in rabbit aortic strips after inhibition of the noradrenaline-metabolizing enzyme. Naunyn-Schmiedeberg's Arch. Pharmacol. 292, 205–217 (1976)Google Scholar
  9. Henseling, M., Rechtsteiner, D., Trendelenburg, U.: The influence of monoamine oxidase and catechol-O-methyl transferase on the distribution of 3H-(±)-noradrenaline in rabbit aortic strips. Naunyn-Schmiedeberg's Arch. Pharmacol. 302, 181–194 (1978a)Google Scholar
  10. Henseling, M., Graefe, K.-H., Trendelenburg, U.: The rate constants for the efflux of the metabolites of noradrenaline from rabbit aortic strips. Naunyn-Schmiedeberg's Arch. Pharmacol. 302, 207–215 (1978b)Google Scholar
  11. Iversen, L. L.: The uptake of catechol amines at high perfusion concentrations in the rat isolated heart: A novel catechol amine uptake process. Br. J. Pharmacol. 25, 18–33 (1965)Google Scholar
  12. Iversen, L. L., Salt, P. J.: Inhibition of catecholamine uptake by steroids in the isolated rat heart. Br. J. Pharmacol. 40, 528–530 (1970)Google Scholar
  13. Iversen, L. L., Salt, P. J., Wilson, H. A.: Inhibition of catecholamine uptake in the isolated rat heart by haloalkylamines related to phenoxybenzamine. Br. J. Pharmacol. 46, 647–657 (1972)Google Scholar
  14. Uhlig, W., Bönisch, H., Trendelenburg, U.: The O-methylation of extraneuronally stored isoprenaline in the perfused heart. Nauyn-Schmiedeberg's Arch. Pharmacol. 283, 245–261 (1974)Google Scholar
  15. Uhlig, W., Fiebig, R., Trendelenburg, U.: The effect of corticosterone on the fluxes of 3H-normetanephrine into and out of the extraneuronal compartments of the perfused rat heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 295, 45–50 (1976)Google Scholar
  16. van Rossum, J. M., Van Ginneken, C. A. M., Henderson, P. Th., Ketelaars, H. C. J., Vree, T. B.: Pharmacokinetics of biotransformation. In: Kinetics of Drug Action (J. M. van Russum, ed.). Handbook of exp. Pharmacol., vol. 47, pp. 125–167. Berlin-Heidelberg-New York: Springer 1977Google Scholar

Copyright information

© Springer-Verlag 1978

Authors and Affiliations

  • H. Bönisch
    • 1
  • K. -H. Graefe
    • 1
  • U. Trendelenburg
    • 1
  1. 1.Institut für Pharmakologie und Toxikologie der Universität WürzburgWürzburgFederal Republic of Germany

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