Effect of tin and lead on porphyrin metabolism in mice.

It is well know that exposure to lead causes disorders of porphyrin metabolism such as elevation of ƒÂ-aminolevulinic acid (ALA) and coproporphyrin (CP) in urine, accumulation of protoporphyrin (PROTO) in erythrocytes, and inhibition of erythrocyte ƒÂ-aminolevulinic acid dehydratase (ALAD) activity.') In addition, it has been reported that inorganic tin (II) also inhibits erythrocyte ALAD activity and elevates the urinary excretion of ALA and CP in rabbits.3-5) However, data concerning the effect of combined exposure to tin and lead on porphyrin metabolism are seldom reported. The main purpose of this study was to investigate the combined effect of tin and lead on porphyrin metabolism in mice using biological parameters such as erythrocyte ALAD activity, erythrocyte PROTO, urinary ALA and urinary CP. Animals and treatment Male ddy mice weighing 40-48g were obtained from Kyudo (Kumamoto, Japan). They were housed in plastic cages in an airconditioned room at 25 •} 2•Ž and exposed to a 12h light/12h dark cycle. Commercial food (Nihon Clea, Tokyo, Japan) and water were given ad libitum. The tin (II) and lead compounds used in all cases consisted of SnC12.2H20 and Pb (CH3C00)2.3H20, respectively. The mice were divided into four groups of six animals each. The control group received 0.9% NaCl i. p. (injection volume; 0.1 ml/50g) every day for 5 days. The tin group was injected i. p. with tin chloride dissolved in 0.9% NaC1 (in a dose of 10ƒÊmol Sn/kg/day) for 5 days. In both groups, sample collection was performed two days after the last injection. The lead group was given drinking water containing lead acetate (100 or 200ppm as Pb) for 7 days together with i. p. injection of 0.9% NaC1 as in the case of the control group. The tin + lead group was exposed to lead (100 or 200