Using atomic absorption spectrophotometry, we measured serum mineral (Fe, Cu, Z n, Mg, Ca, K, Na) concentrations in blood of male athletes participating in a triathlon competition held at Nakajima, Ehime in 1989. The athletes were divided into a young group (n=9, 24.2±3.6 yr) and a middle-aged group (n=9, 49.3±4.4 yr) . Blood samples were taken on the day before the competition, at the finish, on the following day and for eight days after.
Immediately after the race, the concentrations of iron, calcium and potassium were increased significantly in sera taken from both groups, and those of copper and zinc were found to be increased only in the young group. In the middle-aged group, serum magnesium and sodium concentrations were decreased significantly. On the day after the race, most of the serum mineral concentrations had returned to values similar to those measured before the race, although the serum sodium concentration in the middle-aged group was still below the previous value, and this low level persisted for eight days after the race in both groups.
Noticeable differences between the young and middle-aged groups were that recovery of increased iron concentration in serum tended to be prolonged in the middle-aged group, and the concentrations of serum copper and zinc were higher than those in the young group throughout the measurement period, with only small changes evident before and after the race. By contrast, serum potassium concentration in the middle-aged group was lower than in the young group throughout the measurement period.

OBJECTIVESWe studied and compared the possible effects of in utero and lactational exposure to 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) or 3, 3', 4, 4', 5-pentachlorobiphenyl (PCB126) on learning behavior in offspring.

METHODSPregnant Long-Evans Hooded rats were administered either TCDD (50, 200, or 800 ng/kg) or PCB126 (500, 2,000 or 8,000 ng/kg) on gestational day 15. A procedure of schedule-controlled operant behavior was applied to examine learning behavior in the male and female offspring at 11 weeks of age for 30 days. Three indices, namely, response rates in a fixed ratio (FR) and in a differential reinforcement of low rates (DRL), and reward rate in the DRL component in multiple FR 20 DRL 20 s (mult-FR 20 DRL 20-s) test sessions, were used for the evaluation of learning behavior.

RESULTSToxic effects on learning behavior in male and female pups following in utero and lactational exposure to TCDD or PCB126 were observed mainly in the FR learning component. However, no linear dose-dependent effects of either of the two compounds were observed for the above three indices. The response rates of animals in the low-dose TCDD and PCB126 groups decreased and those in medium-dose TCDD and PCB126 groups appeared to induce hyperactive behavior. The high dose of PCB126 appeared to have a distinct toxicity from that of TCDD in terms of the acquisition of learning behavior.

CONCLUSIONSToxicities of PCB126 and TCDD in learning behavior might be similar to each other and the current toxic equivalency factor (TEF) of 0.1 for PCB126 can be considered to be appropriate for this endpoint.