Phase Shifting of the Circadian Clock by Diethylstilbestrol and Related Compounds in Neurospora crassa

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Abstract
Phase shifts of the circadian conidiation rhythm in N. crassa were induced by 3-h treatments of mycelia in liquid medium with diethylstilbestrol (DES), dienestrol (DIE), hexestrol (HEX), diethylstilbestrol dipropionate (DESP) and dienestroldiacetate (DIEA). Over a 24-h period beginning 24 h after the transition from light to constant dark, maximum phase shifts occurred in .apprx. 36 h. DES was the most effective of the drugs tested, giving 10-h phase advances at 20 .mu.M. DIE and HEX caused similar phase shifts as DES at 40 .mu.M. The 2 derivatives of the last, DESP and DIEA, were much less effective in shifting phase; only a few hours of phase advance result from treatments at 80 .mu.M concentrations. The activity of isolated plasma membrane ATPase was inhibited by DES and partially by HEX, but not by DIE, DESP or DIEA. O2 consumption of the mycelia was inhibited equally by DES, DIE and HEX, while DIEA and DESP had little effect. Phase shifts by DES cannot be interpreted as evidence that plasma membrane ATPase is a component of the circadian clock.