Circadian rhythms of RNA, DNA and protein in the rat thyroid, adrenal and testis in chronic pesticide exposure. II. Effects of the herbicides Aminotriazole and Alachlor.

Ninety days of exposure to Aminotriazole (500 ppm/day) leads to changes of the time structure in the rat adrenal and thyroid. The circadian rhythm in adrenal DNA content is not demonstrable in the treated animals as a group phenomenon. There is a phase advance of over five hours (+76 degrees) in the circadian rhythm in adrenal RNA and a phase delay of about nine hours (-136 degrees) in the rhythm in adrenal protein. There is an increase of the mesors (rhythm adjusted mean) and a decrease in the amplitudes of the circadian rhythms in thyroid DNA and RNA content without detectable phase alteraton and a decrease in thyroid protein mesor with a slight but statistically significant phase delay (-25 degrees). The circadian rhythms of the three parameters studied in the testis were not changed by Aminotriazole exposure. Ninety days of exposure to Alachlor (50 ppm/day) had only a minor effect on the testicular rhythms studied. The isolated decrease in thyroid RNA amplitude and the disappearance of the circadian rhythm in adrenal protein content, as a group phenomenon, were the only rhythm alterations found. A chronotoxicological approach may be of importance for the selection to relatively innocuous compounds to be used in agriculture and for the early recognition of undesirable effects in man and animals.