A neutral lipophilic compound of aluminum(III) as a cause of myocardial infarct in the rabbit

Toxicobgy

Letfers,

39 (1987) 185-188

185

Elsevier

TXL 01882

A NEUTRAL LIPOPHILIC COMPOUND OF ALUMlNUM(II1) CAUSE OF MYOCARDIAL INFARCT IN THE RABBIT (Aluminum;

PAOLO

aluminum acetylacetonate;

ZATTAa,

CIORGIO

GIORDANOb,

rabbit heart; myocardial infarct)

BENEDETTO

CORAIN’,

MOSE’

FAVARATOd

and G.

BOMBI’ C.N.R.

“Centro

RENZO

AS A

Metalloproteine,

I-35100

Padua,

bOspedale Civile, I-30081 Dolo, ‘Dipartimento

di

Chimica Inorganica, Metallorganica e Analitica, Universit6 di Padova, I-35131 Padua, and dDipartimenio di Biologia, Universitir di Padova, I-35131 Padua (Italy) (Received

IS June

1987)

(Revision

received

7 August

(Accepted

10 August

1987)

1987)

SUMMARY intravenous lipophilic feature

administration

complex of which

of aluminum(ll1)

acetylacetonate

in the form of the hydrolytically

induces in the rabbit a severe pathological

is the occurrence

of a myocardial

stable and moderately

picture,

the most significant

infarct.

INTRODUCTION

In recent years much attention has been focused on the neurotoxicity of aluminum(III), and the possible involvement of this metal in the etiology of Alzheimer disease appears to be a matter of intensive experimenta research [ 1,2] and medical speculation 13,4]. Moreover, the basic toxicity of aluminum(II1) and, specifically, its neurotoxicity to animals was recently found to be greatly enhanced if the metal is coordinated to ligands, which make it stable towards hydrolysis [5,6]. We report here on some preliminary histopathological findings which demonstrate that Al(acac)s (acac = 2,4_pentanedionate or acetylacetonate) dissolved in water is a strong cardiotoxic agent to rabbits. Address Padua,

for correspondence:

Abbreviations: lactate

Paolo

Zatta,

Centro

C.N.R.

Metalloproteine,

Via Loredan

8, I-35100

Italy. AI(acac)r,

dehydrogenase;

0378-4274/87/$

aluminum m.p.,

03.50 0

2,4-pentanedionate

melting

1987 Elsevier

point;

IR, infrared;

Science

Publishers

or acetylacetonate; NMR,

nuclear

CK, creatine magnetic

B.V. (Biomedical

kinase;

resonance.

Division)

LDH,

186

~tATERlALS

AND

METHODS

A total of 10 New Zealand white rabbits (ca. 3 kg body weight) were given daily a sterile i.v. injection of 3.7 pmol of Al(acac)3 (corresponding to 100 pg of aluminum or ca. 30 @g/kg body weight), in aqueous solution. Blood CK and LDH enzymatic activity tests were performed every 2 days using a commercial kit (Boehringer). Histopathological observations were carried out on tissue samples after 24 h fixation in 10% buffered formalin. Slides were stained with hematoxylin-eosin and Alcian-PAS. Al(acac)j was prepared according to the literature [7] and recrystallized from benzene/n-hexane; its purity was carefully controlled by m.p. measurement, elemental analysis, IR and ‘H-NMR spectrometry. Control experiments were performed on 3 rabbits by injection of comparable molar amounts of free acetylacetone (aqueous solution, 300 pg/day for 16 days). Aluminum analyses in heart tissue were carried out, after dry mineralization, by ionic chromatography. RESULTS

AND

DISCUSSLON

Blood CK (EC 2.7.3.2) of the treated animals reached values ranging from 1500 to 1800 IU just after 2 days, and reached 2000-2300 IU after 5-7 days of treatment (the normal figure is 330 f 76 IU [8]). All rabbits died after 9-10 days, as a consequence of congestive cardiac failure. Histologically, the heart lesions (Figs. 1 and 2) consisted of multiple areas of interstitial hyperplasia, muscle cell necrosis and myocarditis. These lesions were distributed in both ventricles, a marked swelling of the right ventricle being also observed. Hyperplasia of the interstitial spaces among the myocardial fibers contained a loose fibrillary network, which was characterized by a marked basophilia also around the adventitia of the intramyocardial vessels and by the proliferation of hypertrophic fibroblasts. Hyperplasia was associated with edema, particularly in the subendocardial region of the left ventricular wall. Endothelial cell proliferation and endomyocardial fibrosis were not observed. The areas of myocardial cell necrosis were usually small (sometimes unicellular), but in several cases they extended over several fibers. The cells exhibited increased eosinophilia and nuclear picnosis, with homogeneous appearance of the cytoplasm. Remarkably, also cells exhibiting microvacuolation (degenerating cells) or contraction bands [9] were clearly detectable. Necrotic muscle cells were invaded by histiocytes. Multifocal myocarditis was associated with interstitial hyperplasia and myocardial necrosis and was characterized by the presence of histiocytes, lymphocytes and granulocytes, mainly eosinophilic. Histopathological examination of the skeleton muscles gave no evidence of cell alterations; all other organs displayed only secondary damages.

187

Fig. 1. Myocardial

tissue Cram an Al-t~eated labbit showing interstitial infiltrate

Fig.

2. Myocardial

tissue from

an Al-treated

(B) (x

rabbit

IlyperplaGa (4) and ini‘lammatory

450).

showing

cell necrosis with prominent

bands (A) ( x 450) and a wide necrotic area (B) (x

250).

contraction

188

The control sor of the

experiments carried out with free aqueous acetylacetone (the precurligand acetylacetonate) gave no indication of clinical and

histopathological alterations, in agreement with the known low toxicity of this compound [lo]. It has to be concluded that aluminum(II1) is responsible for the toxic action

of Al(acac)J

and,

in fact,

a significant

accumulation

of aluminum

was

observed in the myocardium of treated animals (1.3-2.1 pg Al/g of lyophilized tissue, which is 3-4 times the value found in controls). Our findings point out a novel aspect of aluminum toxicity; further work aimed at ascertaining whether the myocardiopathy herein described is irreversible is now in progress. If this will turn out to be the case, Al(acac)3 will demonstrate to be a convenient chemical species for obtaining experimental models of human myocardial infarcts. In this connection, it is worth pointing out that very few such chemicals are available [l l-131 and moreover the morphological patterns induced by them are more myocarditic than infarctual in character.

REFERENCES 1 D.R. Crapper

McLachlan

Sup. Sanita, 2 P.O.

and B.J. Farnell,

22 (1986) 697-702

Ganroth,

Cellular

and references

mechanisms

and aluminum

toxicity,

Ann.

1st.

Perspect.,

65

therein.

Metabolism

and possible

health

effects of aluminum,

Alzheimer’s

disease (senile dementia):

Environ.

Health

(1986) 363-441. 3 G.G.

Glenner,

dations,

J. Am. Ger. Sot.,

4 P. Zatta,

R. Giordano,

hypothesis, 5 G.G.

Bombi,

B. Corain,

Finnegan,

neurological I R.C. Young 8 M. Favarato il coniglio,

S.J.

interest,

B. Bouchazdy

Bombi,

D. Pagano,

Alzheimer

and critique dementia

A.G. Sesti and P. Zatta,

in P. Vezzadini,

and Aging,

Vol. 8, Eurage

Rettig

C.

and

McReynolds,

and P. Zatta, Innov.

G.G.

neurotoxicity,

J. Am. Chem.

and J.P. Agric.

and

R. Giordano,

System

update

with recommen-

and

the aluminum

Chemical

and biological

(in press).

on aluminum

Neuroendocrine 6 M.M.

B. Corain

Med. Hypotheses

investigations

a research

30 (1982) 59-62.

Orwig,

Sot.,

Amsterdam,

A neutral

and

G.

Labb

(Eds.),

1986, pp. 253-258.

water-soluble

aluminum

complex

of

108 (1986) 5033-5035.

Aluminum

Parametri

A. Facchini

chimico

acetylacetonate,

Inorg.

clinici negli animali

Synth.,

di interesse

2 (1946) 25-26. produttivo.

Parte

I:

(in press).

and G. Majno,

Histopathology

of early myocardial

infarcts,

Am. J. Pathol.,

74 (1974)

301-330. N.1. Sax, Dangerous

Properties

of Industrial

Materials,

6th edn.,

Van Nostrand,

New York,

1984,

p. 102. S.M. Factor, tion. Islands

E.H. Sonneblick and E.S. Kirk, The histologic border or peninsulas?, Am. J. Pathol., 92 (1978) 11 l-124.

M.E. Billingham, induced

Heart

Morphologic

Disease,

changes

T. Balazs, V.J. Ferrans, A. El-Hage, W.L. West, Study of the mechanism Appl.

Pharmacol.,

in drug-induced

Elsevier/North-Holland

zone of acute myocardial

heart disease,

Biomedical

Press,

in M.R. Bristow

Amsterdam,

S.J. Ehrreich, G.L. Johnson, E.H. Herman, of hydralazine-induced myocardial necrosis

59 (1981) 524-534.

infarc-

(Ed.), Drug-

1980, pp. 127-149. J.C. Atkinson and in the rat, Toxicol.