Effect of the female sexual cycle of the activity of delta-aminolaevulinate synthase in rat liver.

The activity of delta-aminolaevulinate synthase was determined in the livers of fed female rats and was found to vary with the phase of their sexual cycle. The highest enzymic activity was obtained during preoestrus (38.0 +/- 3.2 nmol delta-aminolaevulinateg.g liver.-1 hour-1), the lowest during dioestrus (17.4 +/- 3.4 nmol delta-aminolaevulinate.g liver.-1 hour-1). During oestrus and metoestrus the activity of the enzyme was intermediate. The oscillation of the enzymic activity might be significant in the occurence of the ovulocylic form of acute intermittent porphyria.