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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.
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.