2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN (TCDD)-INDUCED CHANGES IN GLUCOSE TRANSPORTING ACTIVITY IN GUINEA-PIGS, MICE, AND RATS IN-VIVO AND IN-VITRO

The toxic action of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on glucose uptake was studied on different species, sexes, and strains of animals by using a nonmetabolizable glucose analog, 3-0-methyl D [1-H-3] glucose (H-3-Me-glc). We have found a drastic reduction in glucose uptake in different organs from male guinea pigs in vivo as well as in vitro. Female guinea pigs were less responsive to this effect of TCDD compared to males. Highly TCDD-responsive mice strains responded in the same way as the male guinea pigs, while less TCDD-responsive mice strains did not. A reduction in glucose uptake was found in explant adipose tissue cultures (in vitro) of male mice (highly TCDD-responsive) after a 4 hour incubation with 10(-8) M TCDD. In less responsive mice strains, stimulation was observed using the same model (in vitro). In the case of male rats, as well as male guinea pigs, glucose uptake was highly reduced by 10(-8) M TCDD using an in vitro system of explant adipose tissue. The Ah-receptor blocker, 4,7-phenanthroline, abolished the effect of TCDD on inhibition of glucose uptake in adipose tissue of male guinea pigs both in vivo and in vitro. Transcription and translation inhibitors (actinomycin D and cycloheximide, respectively) were tested separately or in combination with TCDD using the guinea pig adipose tissue culture model. It was found that actinomycin D could block the effect of TCDD on glucose uptake throughout the experiment time (360 min) while cycloheximide blocked TCDD action for about 60 minutes. Protein kinase inhibitors (e.g., genistein, neomycin) did not change the effect of TCDD on glucose uptake in male guinea pig adipose tissue. Based on these observations, we conclude that TCDD inhibits Me-glc uptake in various organs in guinea pigs, mice, and rats, and this response is mediated by the Ah-receptor.