Coordination of biogenic amines with synaptosomal and vesicular metal ions: Equilibrium and spectral studies in model systems
✍ Scribed by K.S. Rajan; A. Skripkus; G.E. Marks; J.M. Davis
- Publisher
- Elsevier Science
- Year
- 1976
- Weight
- 952 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0006-3061
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✦ Synopsis
Thermodynamic equilibrium studies using model systems were cxried out on the nature and extent of coordination of twelve different biogenic amines and adenosine-5'-triphosphate (ATP) with the bivalent metal ions, viz_, Ca*' and Zn", which occur in the subcellular fractions of the brain, at 25.0 k O.l"C and at an ionic strength of 1.0 (KNO,). In the combined presence of the individual monoamines and ATP the metal ions were predominantly coordinated by ATP in the pH range 3.0 to 6.5 with binding constants (log KML) of 2.84 f 0.06 and 3.19 * 0.39 for the Ca" and Zn2+ chelates, respectively_ Each of the monoamines coordinated with the metal-ATP chelate above pH 6. The stabilities of the chelates of some of the amines with Ca" -ATP (1:l) system were NE, 2.33 i-0.33; AA, 2.24 f 0.19; OA, 1.94 + 0.29; NMeN, 1.60 +-0.22; DA, 2.14 f 0.09. Values for the Zn"+-ATP-amine systems were: NE, 8.35 * 0.26; OA, 4.53 f 0.07; DA, 10.05 ? 0.39. Absorption spectral studies were carried out in order to examine the nature of coordination of NE, DA, TA, and AA with Cu*+, Fe*', and Mg" ions in the combined presence of ATP. Results of the spectral studies taken together with the (thermodynamic) equilibrium data have indicated that in the pH range of biological interest, the catechol amines (NE and DA) and ATP are both coordinated to the "synaptosomal and vesicular" metal ions. The results further indicated that both the pyrocatechol and the ethanolamine groups of NE might be involved in the coordination of Cu'+. However, the interaction of the ethanolamine group of the NE molecule with the rest of the metal ions was not indicated_ INTRGDUCTION In view of the well-known role of the biogenic amines in the control of tranquilizing and antidepressant activities of the body, a knowledge of the