Circadian rhythms of RNA, DNA and protein in the rat thyroid, adrenal and testis, in chronic pesticide exposure. IV. Effects of the herbicide 2,4-dichlorophenoxyacetic acid.

Ninety days of the rats exposure to the herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D)(100 ppm/day) leads to circadian rhythm alterations in the thyroid and the adrenal and to a much lesser degree in the testis. 2,4-D thus affects the time structure of the adrenal and of the thyroid with apparently free-running circadian rhythms in thyroid DNA and adrenal RNA, phase delay in thyroid RNA and phase advance in adrenal DNA. In the testis, the circadian DNA and RNA rhythms ae unchanged, with the exception of a slightly lowered DNA amplitude, and the circadian protein rhythm shows a small but statistically significant phase advance. Sampling without regard for time might lead to erroneous conclusions.