Effects of diazepam on cell division rates and productivity of Scenedesmus obliquus in Synchronous cultures.

Abstract

Scenedesmus cells synchronized by a light-dark regimen of $$14:\overline {10} $$ h were examined after addition of diazepam (Valium) into the suspension medium. Effects on division rates (production of autospores) and on production of DNA, RNA, carbohydrates, chlorophyll, and cell nitrogen were determined. Diazepam added at the start of the cell cycle (i.e., start of illumination) inhibited growth already between 10-5 and 10-4 M. With 10-4 M diazepam the cells do not divide anymore. With 8·10-5 M only a very low division rate and — especially after the first 6 h of the cell cycle — alow production of the observed compounds are measurable. In the presence of diazepam only the amount of RNA (and cell nitrogen) increases during the first 6 h. If the drug is added at theend of illumination, the effects on cell division and on the amounts of carbohydrates, chlorophyll, and cell nitrogen are nearly negligible. A possible latency of diazepam inScenedesmus is discussed. The decrease of the division rate is assumed to be a result of metabolic inhibition.