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

Abstract

Phase shifts of the circadian conidiation rhythm in Neurospora crassa were induced by 3-hour treatments of mycelia in liquid medium with diethylstilbestrol (DES), dienestrol (DIE), hexestrol (HEX), diethylstilbestroldipropionate (DESP), and dienestroldiacetate (DIEA). Over a 24-hour period beginning 24 hours after the transition from light to constant dark, maximum phase shifts occurred about 36 hours. DES was the most effective of the drugs tested, giving 10-hour phase advances at 20 micromolar. DIE and HEX caused similar phase shifts as DES at 40 micromolar. The two 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 micromolar concentrations.The activity of isolated plasma membrane ATPase was inhibited by DES and partially by HEX, but not by DIE, DESP, or DIEA. O(2) 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.