348 Abstracts

NO12 A13+ BINDING TO CATECHOLAMINES AND TIRON. Tamas Kiss and Imre Sovago, Institute of Inorganic and Analytical Chemistry,

L. Kossuth University, Debrecen, Hungary and R. Bruce Martin, Chemistry Department, University of Virginia, Charlottesville, VA 22903, USA.

In order to assess a possible role for A13+ in dementias, its stability constants for binding to four catecholamines have been deter- mined. Because A13+ binds to the catecholate locus with the ammonium group still protonated, conventional treatments are not applicable and the concentration of the chelating microform requires estimation. Owing to the high catecholate basicity, uncertainty in the pKa value for the last phenolic ionization, and the low concentration of the chelating microform, conditional stability constants applicable to pH 7.0 have also been calculated. Tiron is the strongest catecholate A13+ binder in neutral solutions. (J. Am. Chem. Sot., I&, May (1989).

N()l'J ORIGIN OFTHEDOUBLEROLEOF CITRATETOWARDSALUMINIUM INTOXICATION. S. Dayde, M. Venturini and G. Berthon, INSERM U305,

Universite Paul Sabatier, Toulouse, France. Attention has recently been drawn to the toxicity of oral aluminium-containing

drugs such as antacids and phosphate-binding gels. In particular, it has been shown that the blood concentration of aluminium was substantially enhanced following the simultaneous ingestion of aluminium and citrate in humans [l]. On the other hand, parenteral administration of citrate induces aluminium excretion in mice (21. Our computer-based speciation studies clearly indicate that these apparently paradoxical observations are actually due to the predominance of distinct aluminium-citrate complexes, depending on the different physiological conditions involved.

[l] P. Slanina et al., Clin. Chem., 3, 539 (1986). [2] J.L. Domingo et al., Human Toxicol., 1, 259 (1988).

NO14 THE EFFECT OF ALUMINUM SPECIATION ON THE RABBIT ERYTHOCYTES

P. zattaa, M. Perazzolob, M. Favaratob, G.G. Borrtbic, B. CorainC,

Nicolini M d a

, Depart. Biochemistry University of Georgia, Athens, USA

b d Depart. Biology, CChemistry, Pharmacy Universit

1 of Padova, Italy

The target of the biochemical action of AlI' has been investigated

for a possible effect on the cell membrane stability. Neutral and hy-

drolitically stable aluminum complex Al(acac) (acac=acetylacetonate)

showed a marked effect on the membrane stabil?ty of rabbit erythrocytes

in vitro with formation of acanthocytes and a modification of the osmo-

tic fragility. Two hydrophilic complexes of Al"': Al(malt)g(malt=mal-

tol) hydrolytically stable and Al(lact)

no effect.

3 hydrolitically metastable had