Factors Influencing Absorption and Retention of Oral 109Cd in Mice: Age, Pretreatment and Subsequent Treatment with Non‐radioactive Cadmium

The influence of age, pretreatment with CdCl2 and long‐term oral treatment with CdSO4 on whole‐body retention, organ distribution and the biological half‐time of 109CdCl2 (given as a single oral dose) was studied in mice in three separate experiments: I) Male CBA‐mice, 1, 3 and 6 months of age, were given a single oral dose of CdCl2 labelled with 109Cd. The whole‐body retention of the radiolabelled cadmium was inversely related to age. This was explained by a significantly higher intestinal absorption of 109Cd in the younger mice, compared to the older. No influence of age on the biological half‐time of 109Cd was observed. II) Three groups of adult of male CBA‐mice were pretreated with 75 mgCd/l (as CdCl2) in the drinking water for 130, 13 or 0 days, respectively, before receiving a single oral dose of CdCl2 labelled with 109Cd. The two pretreated groups showed higher intestinal absorption of radio‐labelled cadmium and a statistically significant longer biological half‐time of 109Cd compared to mice not pretreated with cadmium. The organ retention of radiolabelled cadmium was markedly higher in mice given cadmium in the drinking water compared with those given deionized water. III) Male and female adult CBA‐mice were exposed to a single oral dose of CdCl2 labelled with 109Cd, via stomachtube. and were thereafter given either deionized water (control group) or 50 mgCd/l (as CdCO4) in the drinking water continuously for 18 months. The organ retention of the radiolabelled cadmium was higher in mice exposed to cadmium in the drinking water compared to those given deionized water. Mice exposed to cadmium via the drinking water had a markedly longer biological half‐time of 109Cd compared to non‐Cd‐exposed mice. In all experiments the animals retaining a larger proportion of the cadmium dose showed higher liver: kidney ratios of the radiolabelled cadmium compared to mice retaining less cadmium. The conclusions of the present studies were: Age is of significant importance to the metabolism of cadmium due to the marked raise in intestinal absorption in the youngest age. pretreatment with cadmium caused a higher intestinal absorption of radiolabelled cadmium. A longer biological hall‐time of 109Cd was seen both after pretreatment and subsequent treatment with cadmium.