TOXICOLOGICAL PROFILE FOR BARIUM AND COMPOUNDS ...

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2. HEALTH EFFECTS
either 0.071, or 0.71 mg/kg/day. In the 4-month study, significant increases
in blood pressure were observed in rats treated with 6.43 mg/kg/day; no change
in blood pressure was observed in rats treated with either 0.0643 or
0.643 mg/kg/day. Significant increases in blood pressure also were noted in
the 16-month study in rats treated with 0.54 and 5.4 mg/kg/day; however, no
effects on blood pressure were noted in the 16-month experiment at
0.054 mg/kg/day. The high-dose group (5.4 mg/kg/day) exposed for 16 months
also had depressed cardiac contraction, depressed cardiac electrical
conductivity, and decreased cardiac ATP, phosphocreatine, and phosphorylation
potential (Kopp et al. 1985; Perry et al. 1983, 1985, 1989).
In contrast to the studies by Perry et al. (1983, 1985, 1989), increased
blood pressure was not observed in one study in which barium was administered
to normotensive rats for an intermediate period at doses up to 15 mg/kg/day in
either drinking water or in 0.9% saline (McCauley et al. 1985). The reason
for the discrepancy between the results of the studies by Perry et al. (1983,
1985, 1989) and the study by McCauley et al. (1985) is not known. As in the
Perry et al. (1983, 1985, 1989) studies, the rats in the study by McCauley et
al. (1985) were maintained on a diet low in barium content. However, it was
not reported by McCauley et al. (1985) whether or not this low barium diet
contained certain other trace metals. Certain metals such as sodium and
potassium can potentially influence blood pressure.
In other studies with rats, intermediate and chronic oral exposure to
barium chloride and barium acetate in drinking water have not been associated
with any changes in heart weight or with any gross or microscopic Lesions of
the heart (Schroeder and Mitchener 1975a; Tardiff et al. 1980).
Additional experiments using uninephrectomized and specially bred Dahl
salt-sensitive and salt-resistant strains of rats revealed no adverse effects
on blood pressure resulting from 16 weeks of exposure to barium doses as high
as 150 mg/kg/day (McCauley et al. 1985). However, no untreated controls were
used in these experiments; thus, these results must be interpreted with
caution. Interestingly, Dahl salt-sensitive rats treated with 15 or 150 mg
barium/kg/day did not experience the normal hypertensive response when given
0.9% NaCl-containing drinking water. Experiments assessing the effect of a
5-month exposure to barium on the cardiac response to an arrythmagenic
challenge with 1-norepinephrine demonstrated a significant increase in reflex
bradycardia when rats were given 37.5 mg barium/kg/day in their drinking water
(McCauley et al. 1985). However, this experiment was confounded by the
presence of barium in the diet of both control and treated animals (estimated
barium intake from diet consumption = 1 mg/kg/day). Without adequate controls
these experiments are difficult to interpret.
Gastrointestinal Effects. All cases of acute oral barium poisoning in
adults exhibit gastrointestinal disturbances as the initial symptoms. These
include gastric pain, vomiting, and diarrhea (Das and Singh 1970; Diengott et