Circadian rhythms of RNA, DNA and protein content in the rat thyroid, adrenal and testis in chronic pesticide exposure. I. Effects of a fungicide (Mancozeb).

Ninety days of exposure to the fungicide Mancozeb, 100 ppm/day, affects the circadian rhythms of RNA, DNA and proteins in the thyroid and adrenal and slightly but statistically significantly, the testicular RNA content in the rat. The thyroid RNA rhythm shows an almost 12-hour phase advance without change in mesor, but with a decrease in amplitude and in the percent of total variability of RNA in the group, attributable to the circadian rhythm (PR). In the adrenal, the circadian rhythm of RNA and DNA is lost as a group phenomenon and the mesor of the circadian rhythm of protein content is elevated. The testicular RNA rhythm shows multiple peaks, suggesting frequency demultiplication and a loss of the circadian rhythm as a group phenomenon. Chronotoxicology appears to be essential in detecting the adverse effects of pesticides.