Effects of dietary calcium acetate on lead subacetate carcinogenicity in kidneys of male Sprague-Dawley rats.

Abstract

Seven groups of 4-week-old male Sprague-Dawley rats, 30 animals/group, were fed for 18 months a commercial chow diet with or without 1% admixture of lead subacetate (Pb-Acet) and 0, 0.3, 1, 3 and 6% of calcium acetate (CaAcet). Feeding a 3% CaAcet-only diet did not produce any pathomorphological effects except for a slight decrease in body weights of the rats to 93% of that seen in the control rats. Feeding the 1% PbAcet-only diet decreased the growth rate of rats to 80% that of the control animals and increased the organ/body weight ratios of the kidneys and livers to 200% and 114% of the corresponding control values. Kidney tumors developed in 45% of the rats treated with PbAcet only, with the earliest appearing at 58 weeks. No tumors of other tissues were found in those rats. Feeding the PbAcet + CaAcet diets reduced the weights of rats from 74% to 54% of that of the control rats and increased the kidney/body weight ratio to 300% that of the control animals. The incidences of renal tumors increased in those rats to an average of 71% (p less than 0.03 versus the PbAcet-only diet), with no significant effects relative to the CaAcet contents in the diets. Primary non-renal tumors were found only occasionally in rats fed the PbAcet + CaAcet diets, without significant differences among the various treatment groups. The renal lead accumulation at 18 months equalled 572 +/- 102, 295 +/- 43, 247 +/- 10, 168 +/- 9, and 162 +/- 6 micrograms/g dry weight (mean +/- S.E.M.; n = 22-24) for the 0, 0.3, 1, 3 and 6% CaAcet in the PbAcet diet, respectively. The hepatic accumulation of lead was 22.2 +/- 0.7 micrograms/g dry weight with no discernible differences among the various PbAcet + CaAcet treatment groups. The results indicate that CaAcet added to the PbAcet diet increases the toxicity of the lead salt, and tends to enhance the renal carcinogenicity of PbAcet, yet decreases the accumulation of lead in the kidneys. No significant adverse effects of the PbAcet and CaAcet treatments on the livers were found.