Aluminium accumulation in some tissues of rats with compromised kidney function induced by cadmium-metallothionein

Two experiments (I and II) were performed to study aluminium accumulation in brain as well as in several other tissues in male Wistar rats. A single intraperitoneal injection of cadmium-metallothionein (CdMT, 0.1-0.4 mg Cd/kg b.wt.) was used to compromise kidney function 12 hr before the final aluminium injection in both experiments. In experiment I, rats were maintained on diets deficient (0.01%, w/w) in calcium (-Ca) or providing adequate (+Ca) dietary calcium (0.9%) for 6 weeks. Among animals given a daily intraperitoneal dose of aluminium chloride (10.8 mg Al/kg per day) on 6 consecutive days there was a tendency towards higher aluminium level in brains of rats with compromised kidney function from CdMT (in -Ca rats: the geometric mean [G] = 288 versus 205 ng/g wet weight [w., wt.], P = 0.07, and in +Ca rats: G = 242 versus 164, P < 0.05) as compared to animals given no CdMT. The results from experiment II (all rats were given aluminium 5.6 mg Al/kg 2 and 12 hr after CdMT injection) demonstrated a higher level of aluminium (G: 41 ng/g w. wt., P < 0.05) in brains of rats with only slightly damaged kidney function (0.1 mg Cd/kg) than in those given no CdMT (G: 29 ng/g w. wt.). It was also observed that 1) calcium deficiency had a statistically significant effect (P < 0.05) in increasing kidney retention of intraperitoneal aluminium (G: 327 micrograms/g w. wt.) as compared to rats with a normal calcium supply in the diet (G: 54 micrograms/g w. wt.); 2) when aluminium concentration in kidney was at and above 54 micrograms/g wet tissue, kidney damage was observed. The above results indicate that compromised kidney function including tubular damage induced by a low-dose of CdMT may play a crucial role in the accumulation of aluminium in brain and other tissues. Since tubular function decreases with age in human populations, these findings in rats may be of considerable importance if a similar phenomenon would occur in humans. Therefore, the possibility of increased aluminium retention in persons with low calcium and high aluminium intakes may need to be further investigated.