Toxicology, 8 (1977) 53--61 © Elsevier/North-Holland Scientific Publishers, Ltd.
COMPARATIVE TOXICITY OF T R I V A L F N T AND H E X A V A L E N T CHROMIUM TO RABBITS II. M O R P H O L O G I C A L CHANGES IN SOME O R G A N S
A.K. MATHUR, SATYA V. CHANDRA and S.K. TANDON Industrial Toxicology Research Centre, Lucknow (India) (Received December 7th, 1976) (Accepted January 16th, 1977)
SUMMARY
Toxicity of trivalent and hexavalent chromium compounds was investigated in experimental rabbits to ascertain health hazards among industrial workers or miners occupationally exposed to such chemicals. Brain, kidney and myocardium showed a tendency to accumulate chromium irrespective of its valency state; the morphological changes were more marked in animals exposed to hexavalent chromium. However, no definite co-relation could be observed between the concentration of the metal and the degree of histological changes in these organs.
INTRODUCTION
Ulceration of skin and nasal mucosa, perforation of nasal septum, chronic irritation, congestion and carcinoma of the respiratory system or certain other systemic abnormalities have frequently been observed among chrome platers, chrome chemical and pigment workers, and leather tanners, which have mainly been attributed to the irritative and corrosive properties of hexavalent chromium compounds, the monochromates and dichromates used in these industries [1--6]. The toxicity of hexavalent chromium compounds has also been demonstrated in experimental animals [2,7--9]. The chromates have particularly been responsible for marked biochemical and pathomorphological changes in certain vital organs of the animals such as kidney [10,11] and myocardium [12] owing to their higher solubility and absorption in the system. The c o m p o u n d s of chromium in trivalent state particularly the chromite ores, on the other hand have been considered to possess a low degree of toxicity due to their biological inertness, comparatively
53
low solubility and consequently poor absorption in the system [4,9,13]. However, Heuper and Payne [14] observed that some highly water-soluble trivalent chromium c o m p o u n d s produce cancers when brought in contact with the tissues and some others found them to cause allergy or dermatitis among sensitive persons and leather industry Workers [15--17]. Thus, in view of a considerable part played by such trivalent chromium compounds in chrome industry [18] and the fact that various hexavalent chromium compounds are reduced into trivalent form after entry into the system [4,6], the evaluation of the toxic potentials of chromium in this oxidation state, in relation to that in oxidation state 6, needs thorough investigation. This communication, therefore, deals with the comparative account of the morphological changes in relation to chromium accumulation in some vital organs of experimental rabbits exposed to trivalent and hexavalent chromium c o m p o u n d s for t w o different durations. MATERIALS AND METHODS
I.T.R.C. colony bred male rabbits with an average weight of 1.5 kg, maintained on standard pellet diet, were divided into 3 groups, 2 containing 10 animals each and the third consisting of 8. The rabbits of groups I and II were administered intraperitoneally a dose of 2 mg Cr/kg as chromium nitrate (trivalent chromium) and as potassium dichromate (hexavalent chromium) (E. Merck, G.R.) dissolved in 1 ml of 0.9% NaC1, respectively, daily for 6 weeks. The animals of group III received normal saline alone which served as control. All the animals were weighed every week and the dose adjusted accordingly. A set of 5 animals from each of the groups I and II and 4 from group III were killed at 3 and at 6 weeks of the experiment, 72 h after the last injection. The 72-h period was necessary to allow excretion of most of the u n b o u n d chromium from the system. Immediately after killing, brain, kidney and myocardium were removed, washed thoroughly and divided for histopathological examination and chromium estimation.
Estimation of chromium Chromium was estimated in different tissues by the spectrophotometeric m e t h o d of Gooderson and Salt [19] employing wet ashing procedure.
His topa thological studies A piece of t h e tissues was fixed in 10% formalin buffer for at least a week. After routine processing, the tissues were e m b e d d e d in paraffin, sections of 5 pm were cut o u t with a Wesbox microtome and stained with haematoxylin-eosin for microscopic examination.
54
RESULTS
All the animals remained apparently normal up t 9 t h e m o m e n t of sacririce. Marked congestion in brain, kidney and myocardium of rabbits treated with trivalent and hexavalent chromium c o m p o u n d s for 3 and 6 weeks was observed on gross examination. Brain
Administration of trivalent chromium to rabbits for 3 weeks produced occasional neuronal degeneration in the cerebral cortex ' marked chromatolysis and nuclear changes in the neurones. Further exposure to the metal in trivalent state for 6 weeks caused marked neuronal degeneration in the cerebral cortex accompanied by neuronophagia, neuroglial proliferation and meningeal congestion (Fig. 1). Brain of animals injected hexavalent chromium for 3 weeks, was congested with perivascular infiltration by inflammatory cells. Some neurones in the cerebral cortex had pyknotic nuclei and showed dissolution of Nissl's substance. Neuronophagia and focal neuroglial proliferation were evident throughout the cerebral cortex {Fig. 2). Administration of hexavalent chromium for 6 weeks did n o t alter the histology of the brain significantly from that observed at 3 weeks.
Fig. 1. Cerebral cortex from a rabbit, treated with trivalent chromium for 6 weeks, showing neuronal degeneration and neuroglial proliferation. H and E, × 166.
55
Fig. 2. Cerebral cortex from a rabbit treated with hexavalent chromium showing neuronal degeneration and neuronophagia. H and E, X 664.
The accumulation of chromium with hexavalent chromium than in there was no significant change in ment with both forms of the metal
for 3 weeks,
in brain was far higher in rabbits treated those exposed to trivalent chromium and its level from 3 to 6 weeks of the treat(Table I).
Kidneys
Kidneys from rabbits exposed to trivalent chromium for 3 weeks had marked congestion and extravasation of red blood cells in the intertubular spaces. Marked tubular necrosis accompanied by infiltration with mononuclear cells was also observed (Fig. 3). Further treatment up to 6 weeks did not produce any additional change in the morphology of kidney. The kidneys from animals administered hexavalent chromium for 3 weeks were
56
TABLE I C H R O M I U M C O N C E N T R A T I O N (/~g/g F R E S H T I S S U E ) IN T H E O R G A N S O F R A B BITS A F T E R D A I L Y A D M I N I S T R A T I O N OF C H R O M I U M N I T R A T E ( T R I V A L E N T ) AND POTASSIUM DICHROMATE (HEXAVELENT) FOR 3 AND 6 WEEKS E a c h value r e p r e s e n t t h e m e a n ± S.E. o f 6 r a b b i t s in c o n t r o l a n d 5 in e x p e r i m e n t a l g r o u p s , a p < 0 . 0 0 1 , b p < 0 . 0 5 w h e n c o m p a r e d t o c o n t r o l as e v a l u a t e d b y S t u d e n t ' s ' t ' test. Control
Trivalent chromium
Hexavalent chromium (weeks)
Brain Kidney Myocardium
0.8 ± 0 . 1 4 1.0 ± 0 . 5 8 0.4 ± 0 . 3 0
3
6
3
6
1.6 ± 0 . 3 6 b 19.7 ± 2 . 7 2 a 7.1 ± 0 . 5 3 a
1.3 ± 0 . 3 3 2 7 . 0 +- 3 . 7 3 a 1 4 . 5 ± 1.77 a
4.1 -+ 0 . 2 9 a 4.5+- 1 . 1 9 b 12.9 ± 0 . 4 6 a
5.5 +- 0 . 1 6 a 10.7 +- 0 . 5 2 a 2 4 . 4 -+ 2 . 0 0 a
Fig. 3. K i d n e y f r o m a r a b b i t , t r e a t e d w i t h t r i v a l e n t c h r o m i u m f o r 3 w e e k s , s h o w i n g n e c r o s i s o f t h e t u b u l a r e p i t h e l i u m . H a n d E, × 6 6 4 .
57
Fig. 4. Kidney from a rabbit, treated with hexavalent chromium for 3 weeks, showing tubular necrosis and eosinophilic material in the lumen of tubules. H and E, x 664.
markedly congested and the walls of small blood vessels particularly near some of the glomeruli were thickened and hyaline. At places glomerular tufts were shrunken while proliferation of endothelial cells obliterating the Bowman space was seen in some glomeruli. There was necrosis and irregular desquamation of the epithelium of convoluted tubules, at places eosinophilic hyaline material was seen lying in the lumen (Fig. 4), and the interstitial tissue was seen infiltrated with mononuclear cells and lymphocytes. At places plenty of r e d blood cells were seen lying in between intertubular spaces. Similar changes were observed in the kidneys from the animals treated up to 6 weeks. The accumulation of chromium was f o u n d to be far higher in the kidney of the animals treated with trivalent chromium than in those exposed to hexavalent chromium at both time intervals. There was a significant increase in the metal concentration in kidney from 3 to 6 weeks of chromium administration {Table I).
MyoCardium Myocardium of the animals exposed to trivalent chromium for 3 weeks presented normal architecture. However, the myocardium from the animals treated for 6 weeks, showed marked congestion and degenerative changes of the muscle fibres particularly in the sub-endocardial region. The cyto-
58
Fig. 5. Myocardium from a rabbit, treated with trivalent chromium for 6 weeks, showing degeneration and vacuolation of muscle fibres. H and E, x664.
plasm of the degenerated muscle fibres was vacuolated and the p y k n o t i c nuclei were seen lying at the periphery of the vacuoles (Fig. 5). The mononuclear cells were seen infiltrating the interstitial tissue. The exposure to hexavalent c h r o m i u m for 3 weeks pr oduced no abnormality in m y o c a r d i u m while further t r e a t m e n t up to 6 weeks p r o d u c e d almost similar changes as observed with trivalent c h r o m i u m at 6 weeks interval. The c o n c e n t r a t i o n o f c h r o m i u m was higher in the m y o c a r d i u m of the animals exposed to hexavalent c hr om i um than in those treated with the trivalent form. Further, the levels of the metal in m y o c a r d i u m at a 6-week interval were almost twice as much as observed at 3 weeks with b o t h the forms o f c h r o m i u m (Table I). DISCUSSION The present studies indicated that the administration o f chrom i um in two different o xi da t i on states cause varying degrees of metal accumulation and morphological alterations in brain, kidney and m y o c a r d i u m o f experimental rabbits and t hat there is no definite co-relation between metal concent rat i on and the e x t e n t of tissue injury. Kidney accumulated far more metal than brain and m y o c a r d i u m in animals exposed t o the trivalent form, while histol-
59
ogical changes in the three organs were quite comparable. Similarly, myocardium, despite higher metal accumulation s h o w e d : l e s s morphological alterations than brain and kidney in animals treated with the hexavalent form. Such variations may be due to the differences in the structure or functions o f various organs or their sensitivity towards the two forms of chromium. Although the mechanism by which the two forms o f chrom i um exert their toxic effects is not understood, the results indicate t h a t the metal in oxidation state 6 is more toxic. Baetjer et al. [9] have also report ed hexavalent c h r o m i u m to be more t oxi c than the trivalent form, when i nt roduced systemically. The findings on the morphological changes in kidney and myocardium due to hexavalent c hr om i um observed in the present investigation are also in good agreement with those of some previous workers [7,10--12]. Since c h r o m i u m induced thickening of blood vessels in kidney, the perivascular inflammation in brain and the degeneration o f myofibrils in the endocardial region indicative o f cardiovascular ischaemia, it may be suggested that the metal irrespective of its valancy state may affect the vascular system initially. Vascular disorders in early stage of chrom i um intoxication have also been reported by Yaglinskii and Shabano [7]. However, the mechanism o f systemic t oxi ci t y o f c hrom i um needs furt her investigation. Several previous investigators have observed t hat the hexavalent chromium c o m p o u n d s are highly toxic due to their ready absorption while trivalent c o m p o u n d s are least owing to their p o o r absorption in the system [4,9]. Our findings in this direction, clearly indicate that the water-soluble trivalent ch r o miu m c o m p o u n d s are also toxic t o an appreciable e x t e n t and therefore precautionary measures must be taken by industrial workers handling such salts [3,18]. ACKNOWLEDGEMENTS The authors are grateful t o Dr. S,H. Zaidi, Director of the Centre for the support o f this work, to Messrs. I. Ansari and Surendra Singh f o r t e c h n i c a l assistance and to Mr. M. Ahmad for p h o t o m i c r o g r a p h y . REFERENCES 1 M. Kleinfeld and A. Rosso, Ind. Med. Surg., 34 (1965) 242. 2 E. Browning, Toxicity of Industrial Metals, 2nd ed., Butterworth, London, 1969, p. 119. 3 M. Barborik, Ind. Med. Surg., 39 (1970) 221. 4 A.M. Baetjer, D.J. Birmingham, P.E. Enterline, W. Mertz and J.O. Pierce II, Chromium, National Academy of Sciences, Washington, D.C., 1974, p. 42. 5 P.E. Enterline, J. Occup. Med., 16 (1974) 523. 6 H. Royle, Environ. Res., 10 (1975) 39. 7 V.A. Yaglinskii and A.M. Shabanov, Ref. Zh. Otd. Vyp. Farmakol. Toksikoi. No. 13.54.379 (1965) B~ol. Abst., 49 (1968) 78519. 8 M. Kuschner and S. Laskin, Am. J. Pathoi., 64 {1971) 183. 9 A.M. Baetzer, D.J. Birmingham, P.E. Enterline, W. Mertz and J.O. Pierce II, Chromium, National Academy of Sciences, Washington, D.C., 1974, p. 74.
60
10 A.D.W. Baines, Am. J. Pathol., 47 (1965) 851. 11 W.O. Berndt, J. Toxicol. Environ. Hlth., 1(3} {1976} 449. 12 A.M. Shakhnazarov, Arkh. Pathol., 35(11) (1973) 67; Chem. Abst., 80 (1974) 56234Y. 13 U.S. Public Health Service Publication No. 192, P. 131 (1954), Federal Security Agency, U.S. Government Printing Office, Washington, D.C. 14 W.C. Hueper and W.W. Payne, Arch. Environ. Hlth., 5 (1962) 445. 15 E:'Skog, Acta Derm. Venereol., 35 (1955) 393. 16 G.E. Morris, Am. Med. Assoc. Arch. Dermatol. 78 (1958) 612. 17 S. Fregert and H. Rorsman, Arch. Dermatol. 90 (1964) 4. 18 A.M. Baetjer, D.J. Birmingham, P.E. Enterline, W. Mertz and J.O. Pierce II, Chromium, National Academy of Sciences, Washington, D.C., 1974, p. 17. 19 G.Y. Gooderson and F.J. Salt, Lab. Pract., 17 (1968) 921.
61
COMPARATIVE TOXICITY OF T R I V A L F N T AND H E X A V A L E N T CHROMIUM TO RABBITS II. M O R P H O L O G I C A L CHANGES IN SOME O R G A N S
A.K. MATHUR, SATYA V. CHANDRA and S.K. TANDON Industrial Toxicology Research Centre, Lucknow (India) (Received December 7th, 1976) (Accepted January 16th, 1977)
SUMMARY
Toxicity of trivalent and hexavalent chromium compounds was investigated in experimental rabbits to ascertain health hazards among industrial workers or miners occupationally exposed to such chemicals. Brain, kidney and myocardium showed a tendency to accumulate chromium irrespective of its valency state; the morphological changes were more marked in animals exposed to hexavalent chromium. However, no definite co-relation could be observed between the concentration of the metal and the degree of histological changes in these organs.
INTRODUCTION
Ulceration of skin and nasal mucosa, perforation of nasal septum, chronic irritation, congestion and carcinoma of the respiratory system or certain other systemic abnormalities have frequently been observed among chrome platers, chrome chemical and pigment workers, and leather tanners, which have mainly been attributed to the irritative and corrosive properties of hexavalent chromium compounds, the monochromates and dichromates used in these industries [1--6]. The toxicity of hexavalent chromium compounds has also been demonstrated in experimental animals [2,7--9]. The chromates have particularly been responsible for marked biochemical and pathomorphological changes in certain vital organs of the animals such as kidney [10,11] and myocardium [12] owing to their higher solubility and absorption in the system. The c o m p o u n d s of chromium in trivalent state particularly the chromite ores, on the other hand have been considered to possess a low degree of toxicity due to their biological inertness, comparatively
53
low solubility and consequently poor absorption in the system [4,9,13]. However, Heuper and Payne [14] observed that some highly water-soluble trivalent chromium c o m p o u n d s produce cancers when brought in contact with the tissues and some others found them to cause allergy or dermatitis among sensitive persons and leather industry Workers [15--17]. Thus, in view of a considerable part played by such trivalent chromium compounds in chrome industry [18] and the fact that various hexavalent chromium compounds are reduced into trivalent form after entry into the system [4,6], the evaluation of the toxic potentials of chromium in this oxidation state, in relation to that in oxidation state 6, needs thorough investigation. This communication, therefore, deals with the comparative account of the morphological changes in relation to chromium accumulation in some vital organs of experimental rabbits exposed to trivalent and hexavalent chromium c o m p o u n d s for t w o different durations. MATERIALS AND METHODS
I.T.R.C. colony bred male rabbits with an average weight of 1.5 kg, maintained on standard pellet diet, were divided into 3 groups, 2 containing 10 animals each and the third consisting of 8. The rabbits of groups I and II were administered intraperitoneally a dose of 2 mg Cr/kg as chromium nitrate (trivalent chromium) and as potassium dichromate (hexavalent chromium) (E. Merck, G.R.) dissolved in 1 ml of 0.9% NaC1, respectively, daily for 6 weeks. The animals of group III received normal saline alone which served as control. All the animals were weighed every week and the dose adjusted accordingly. A set of 5 animals from each of the groups I and II and 4 from group III were killed at 3 and at 6 weeks of the experiment, 72 h after the last injection. The 72-h period was necessary to allow excretion of most of the u n b o u n d chromium from the system. Immediately after killing, brain, kidney and myocardium were removed, washed thoroughly and divided for histopathological examination and chromium estimation.
Estimation of chromium Chromium was estimated in different tissues by the spectrophotometeric m e t h o d of Gooderson and Salt [19] employing wet ashing procedure.
His topa thological studies A piece of t h e tissues was fixed in 10% formalin buffer for at least a week. After routine processing, the tissues were e m b e d d e d in paraffin, sections of 5 pm were cut o u t with a Wesbox microtome and stained with haematoxylin-eosin for microscopic examination.
54
RESULTS
All the animals remained apparently normal up t 9 t h e m o m e n t of sacririce. Marked congestion in brain, kidney and myocardium of rabbits treated with trivalent and hexavalent chromium c o m p o u n d s for 3 and 6 weeks was observed on gross examination. Brain
Administration of trivalent chromium to rabbits for 3 weeks produced occasional neuronal degeneration in the cerebral cortex ' marked chromatolysis and nuclear changes in the neurones. Further exposure to the metal in trivalent state for 6 weeks caused marked neuronal degeneration in the cerebral cortex accompanied by neuronophagia, neuroglial proliferation and meningeal congestion (Fig. 1). Brain of animals injected hexavalent chromium for 3 weeks, was congested with perivascular infiltration by inflammatory cells. Some neurones in the cerebral cortex had pyknotic nuclei and showed dissolution of Nissl's substance. Neuronophagia and focal neuroglial proliferation were evident throughout the cerebral cortex {Fig. 2). Administration of hexavalent chromium for 6 weeks did n o t alter the histology of the brain significantly from that observed at 3 weeks.
Fig. 1. Cerebral cortex from a rabbit, treated with trivalent chromium for 6 weeks, showing neuronal degeneration and neuroglial proliferation. H and E, × 166.
55
Fig. 2. Cerebral cortex from a rabbit treated with hexavalent chromium showing neuronal degeneration and neuronophagia. H and E, X 664.
The accumulation of chromium with hexavalent chromium than in there was no significant change in ment with both forms of the metal
for 3 weeks,
in brain was far higher in rabbits treated those exposed to trivalent chromium and its level from 3 to 6 weeks of the treat(Table I).
Kidneys
Kidneys from rabbits exposed to trivalent chromium for 3 weeks had marked congestion and extravasation of red blood cells in the intertubular spaces. Marked tubular necrosis accompanied by infiltration with mononuclear cells was also observed (Fig. 3). Further treatment up to 6 weeks did not produce any additional change in the morphology of kidney. The kidneys from animals administered hexavalent chromium for 3 weeks were
56
TABLE I C H R O M I U M C O N C E N T R A T I O N (/~g/g F R E S H T I S S U E ) IN T H E O R G A N S O F R A B BITS A F T E R D A I L Y A D M I N I S T R A T I O N OF C H R O M I U M N I T R A T E ( T R I V A L E N T ) AND POTASSIUM DICHROMATE (HEXAVELENT) FOR 3 AND 6 WEEKS E a c h value r e p r e s e n t t h e m e a n ± S.E. o f 6 r a b b i t s in c o n t r o l a n d 5 in e x p e r i m e n t a l g r o u p s , a p < 0 . 0 0 1 , b p < 0 . 0 5 w h e n c o m p a r e d t o c o n t r o l as e v a l u a t e d b y S t u d e n t ' s ' t ' test. Control
Trivalent chromium
Hexavalent chromium (weeks)
Brain Kidney Myocardium
0.8 ± 0 . 1 4 1.0 ± 0 . 5 8 0.4 ± 0 . 3 0
3
6
3
6
1.6 ± 0 . 3 6 b 19.7 ± 2 . 7 2 a 7.1 ± 0 . 5 3 a
1.3 ± 0 . 3 3 2 7 . 0 +- 3 . 7 3 a 1 4 . 5 ± 1.77 a
4.1 -+ 0 . 2 9 a 4.5+- 1 . 1 9 b 12.9 ± 0 . 4 6 a
5.5 +- 0 . 1 6 a 10.7 +- 0 . 5 2 a 2 4 . 4 -+ 2 . 0 0 a
Fig. 3. K i d n e y f r o m a r a b b i t , t r e a t e d w i t h t r i v a l e n t c h r o m i u m f o r 3 w e e k s , s h o w i n g n e c r o s i s o f t h e t u b u l a r e p i t h e l i u m . H a n d E, × 6 6 4 .
57
Fig. 4. Kidney from a rabbit, treated with hexavalent chromium for 3 weeks, showing tubular necrosis and eosinophilic material in the lumen of tubules. H and E, x 664.
markedly congested and the walls of small blood vessels particularly near some of the glomeruli were thickened and hyaline. At places glomerular tufts were shrunken while proliferation of endothelial cells obliterating the Bowman space was seen in some glomeruli. There was necrosis and irregular desquamation of the epithelium of convoluted tubules, at places eosinophilic hyaline material was seen lying in the lumen (Fig. 4), and the interstitial tissue was seen infiltrated with mononuclear cells and lymphocytes. At places plenty of r e d blood cells were seen lying in between intertubular spaces. Similar changes were observed in the kidneys from the animals treated up to 6 weeks. The accumulation of chromium was f o u n d to be far higher in the kidney of the animals treated with trivalent chromium than in those exposed to hexavalent chromium at both time intervals. There was a significant increase in the metal concentration in kidney from 3 to 6 weeks of chromium administration {Table I).
MyoCardium Myocardium of the animals exposed to trivalent chromium for 3 weeks presented normal architecture. However, the myocardium from the animals treated for 6 weeks, showed marked congestion and degenerative changes of the muscle fibres particularly in the sub-endocardial region. The cyto-
58
Fig. 5. Myocardium from a rabbit, treated with trivalent chromium for 6 weeks, showing degeneration and vacuolation of muscle fibres. H and E, x664.
plasm of the degenerated muscle fibres was vacuolated and the p y k n o t i c nuclei were seen lying at the periphery of the vacuoles (Fig. 5). The mononuclear cells were seen infiltrating the interstitial tissue. The exposure to hexavalent c h r o m i u m for 3 weeks pr oduced no abnormality in m y o c a r d i u m while further t r e a t m e n t up to 6 weeks p r o d u c e d almost similar changes as observed with trivalent c h r o m i u m at 6 weeks interval. The c o n c e n t r a t i o n o f c h r o m i u m was higher in the m y o c a r d i u m of the animals exposed to hexavalent c hr om i um than in those treated with the trivalent form. Further, the levels of the metal in m y o c a r d i u m at a 6-week interval were almost twice as much as observed at 3 weeks with b o t h the forms o f c h r o m i u m (Table I). DISCUSSION The present studies indicated that the administration o f chrom i um in two different o xi da t i on states cause varying degrees of metal accumulation and morphological alterations in brain, kidney and m y o c a r d i u m o f experimental rabbits and t hat there is no definite co-relation between metal concent rat i on and the e x t e n t of tissue injury. Kidney accumulated far more metal than brain and m y o c a r d i u m in animals exposed t o the trivalent form, while histol-
59
ogical changes in the three organs were quite comparable. Similarly, myocardium, despite higher metal accumulation s h o w e d : l e s s morphological alterations than brain and kidney in animals treated with the hexavalent form. Such variations may be due to the differences in the structure or functions o f various organs or their sensitivity towards the two forms of chromium. Although the mechanism by which the two forms o f chrom i um exert their toxic effects is not understood, the results indicate t h a t the metal in oxidation state 6 is more toxic. Baetjer et al. [9] have also report ed hexavalent c h r o m i u m to be more t oxi c than the trivalent form, when i nt roduced systemically. The findings on the morphological changes in kidney and myocardium due to hexavalent c hr om i um observed in the present investigation are also in good agreement with those of some previous workers [7,10--12]. Since c h r o m i u m induced thickening of blood vessels in kidney, the perivascular inflammation in brain and the degeneration o f myofibrils in the endocardial region indicative o f cardiovascular ischaemia, it may be suggested that the metal irrespective of its valancy state may affect the vascular system initially. Vascular disorders in early stage of chrom i um intoxication have also been reported by Yaglinskii and Shabano [7]. However, the mechanism o f systemic t oxi ci t y o f c hrom i um needs furt her investigation. Several previous investigators have observed t hat the hexavalent chromium c o m p o u n d s are highly toxic due to their ready absorption while trivalent c o m p o u n d s are least owing to their p o o r absorption in the system [4,9]. Our findings in this direction, clearly indicate that the water-soluble trivalent ch r o miu m c o m p o u n d s are also toxic t o an appreciable e x t e n t and therefore precautionary measures must be taken by industrial workers handling such salts [3,18]. ACKNOWLEDGEMENTS The authors are grateful t o Dr. S,H. Zaidi, Director of the Centre for the support o f this work, to Messrs. I. Ansari and Surendra Singh f o r t e c h n i c a l assistance and to Mr. M. Ahmad for p h o t o m i c r o g r a p h y . REFERENCES 1 M. Kleinfeld and A. Rosso, Ind. Med. Surg., 34 (1965) 242. 2 E. Browning, Toxicity of Industrial Metals, 2nd ed., Butterworth, London, 1969, p. 119. 3 M. Barborik, Ind. Med. Surg., 39 (1970) 221. 4 A.M. Baetjer, D.J. Birmingham, P.E. Enterline, W. Mertz and J.O. Pierce II, Chromium, National Academy of Sciences, Washington, D.C., 1974, p. 42. 5 P.E. Enterline, J. Occup. Med., 16 (1974) 523. 6 H. Royle, Environ. Res., 10 (1975) 39. 7 V.A. Yaglinskii and A.M. Shabanov, Ref. Zh. Otd. Vyp. Farmakol. Toksikoi. No. 13.54.379 (1965) B~ol. Abst., 49 (1968) 78519. 8 M. Kuschner and S. Laskin, Am. J. Pathoi., 64 {1971) 183. 9 A.M. Baetzer, D.J. Birmingham, P.E. Enterline, W. Mertz and J.O. Pierce II, Chromium, National Academy of Sciences, Washington, D.C., 1974, p. 74.
60
10 A.D.W. Baines, Am. J. Pathol., 47 (1965) 851. 11 W.O. Berndt, J. Toxicol. Environ. Hlth., 1(3} {1976} 449. 12 A.M. Shakhnazarov, Arkh. Pathol., 35(11) (1973) 67; Chem. Abst., 80 (1974) 56234Y. 13 U.S. Public Health Service Publication No. 192, P. 131 (1954), Federal Security Agency, U.S. Government Printing Office, Washington, D.C. 14 W.C. Hueper and W.W. Payne, Arch. Environ. Hlth., 5 (1962) 445. 15 E:'Skog, Acta Derm. Venereol., 35 (1955) 393. 16 G.E. Morris, Am. Med. Assoc. Arch. Dermatol. 78 (1958) 612. 17 S. Fregert and H. Rorsman, Arch. Dermatol. 90 (1964) 4. 18 A.M. Baetjer, D.J. Birmingham, P.E. Enterline, W. Mertz and J.O. Pierce II, Chromium, National Academy of Sciences, Washington, D.C., 1974, p. 17. 19 G.Y. Gooderson and F.J. Salt, Lab. Pract., 17 (1968) 921.
61
