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Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 278, Issue 3, pp 323–327 | Cite as

Michaelis-Menten kinetics of secretion of sympathetic neurotransmitter as a function of external calcium: Effect of graded alpha-adrenoceptor blockade

  • Lennart Stjärne
Short Communication

Summary

The curve describing the calcium dependence of nerve stimulation induced secretion of tritium labelled noradrenaline (3H-NA) from isolated guinea-pig vas deferens was sigmoid in shape. Graded alpha-adrenoceptor blockade dose dependently moved the curve to the left and shifted it into a rectangular hyperbola. A double reciprocal plot of the fractional secretion of 3H-NA against the calcium concentration in the medium, during disinhibition of the secretory mechanism by alpha-adrenoceptor blockade, yielded a straight line. This indicates that the disinhibited secretory mechanism is basically a simple function of the calcium concentration in the medium, obeying classical Michaelis-Menten kinetics, and normally proceeding at a calcium concentration close to that which gives half maximal secretory rate.

Key words

Kinetics Noradrenaline Secretion Calcium Alpha-Adrenoceptor 

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Copyright information

© Springer-Verlag 1973

Authors and Affiliations

  • Lennart Stjärne
    • 1
  1. 1.Department of PhysiologyKarolinska InstitutetStockholmSweden

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