potassium-perchlorate and Cocarcinogenesis

Early life exposure to certain kinds of chemicals is of concern because of a possible increase in cancer risk, but relevant data are limited. In the present experiment, modifying effects of prepubertal administration of potassium perchlorate (KClO(4)) and tetrabromobisphenol A (TBBPA) on susceptibility to multi-organ carcinogenesis were evaluated. F344 dam rats were administered 0% (control), 0.01%, 0.1% or 1% TBBPA in diet or 0.01% KClO(4) in drinking water after parturition. Their weaned offspring in each group were treated for 2 weeks in the same manner. From 6 weeks of age, all offspring were treated with N-bis(2-hydroxypropyl)nitrosamine in drinking water for 4 weeks. In addition the females at 7 weeks of age were gavaged once with 7,12-dimethylbenz(a)anthracene. At weeks 39 and 47 of age, the males and females, respectively, were euthanized and the liver, kidney, lung, esophagus, thyroid, urinary bladder, testis, epididymis, ovary and mammary gland were histopathologically examined. The incidences of thyroid follicular adenomas in 1% TBBPA females (p<0.05) and of transitional cell papillomas in the urinary bladder of 0.01%, 0.1% and 1% TBBPA females were increased (p<0.05) as compared to the controls. These results indicate that prepubertal exposure to TBBPA raises susceptibility to thyroid and urinary bladder tumorigenesis in rats. Although causes of the effect on thyroid carcinogenesis might be direct and/or indirect hormonal actions, further studies are needed for confirmation.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Age Factors; Animals; Carcinogenicity Tests; Cocarcinogenesis; Female; Male; Mammary Neoplasms, Experimental; Neoplasms, Experimental; Nitrosamines; Perchlorates; Polybrominated Biphenyls; Potassium Compounds; Rats; Rats, Inbred F344; Thyroid Neoplasms

The effect of 1000 ppm potassium perchlorate (KClO4), 1000 ppm potassium iodide (KI) or 1000 ppm propylthiouracil (PTU) in the diet on the development of thyroid tumors was studied histologically and biochemically in Wistar rats given a single ip injection of 280 mg of N-bis(2-hydroxypropyl)nitrosamine (DHPN) per 100 g body weight. Basal diet containing 100 ppm KClO4, 1000 ppm KI or 1000 ppm PTU was given for 19 weeks from week 2 to week 20. The incidence of thyroid adenomas at the end of week 20 of the experiment was 100% (20/20) in rats treated with DHPN followed by KClO4, 85% (17/20) in rats given DHPN followed by KI, 95% (19/20) in rats given DHPN followed by PTU, and 5% (1/20) in rats given DHPN alone. The incidence of thyroid cancers was 100% (20/20) in rats treated with DHPN followed by KClO4, 65% (13/20) in rats treated with DHPN followed by KI and 0% (0/20) in rats treated with DHPN followed by or not followed by PTU. Rats given KClO4, KI or PTU alone and untreated rats had no thyroid tumors. The mean values of TSH in serum were 2.94 +/- 0.79 ng/ml in rats treated with DHPN followed by KClO4, 9.40 +/- 16.0 ng/ml in rats treated with DHPN followed by KI and 60.94 +/- 20.60 ng/ml in rats treated with DHPN followed by PTU. It was confirmed that (1) KClO4, PTU and KI promote the development of thyroid tumor in rats treated with DHPN, (2) the promoting effect of KClO4 or KI is stronger than that of PTU and (3) the value of TSH in serum is not parallel to the promoting effect on the development of thyroid tumor.

Topics: Animals; Body Weight; Cocarcinogenesis; Male; Nitrosamines; Organ Size; Perchlorates; Potassium; Potassium Compounds; Potassium Iodide; Propylthiouracil; Radioimmunoassay; Rats; Rats, Inbred Strains; Thyroid Gland; Thyroid Neoplasms