Effect of certain anaesthetic agents on the activity of rat hepatic delta-aminolaevulinate synthase.

The activity of delta-aminolaevulinic acid synthase (E.C.2.3.1.37) (the rate-limiting enzyme for haem and porphyrin biosynthesis) has been measured in the rat liver after the repeated administration of anaesthetic agents in vivo. The activity of the enzyme was increased by Althesin, chlordiazepoxide, enflurane, etomidate, lignocaine, methohexitone, methoxyflurane, pentazocine and thiopentone and decreased by procaine. No significant changes in activity occurred after the administration of amethocaine, atropine, bupivacaine, diazepam, droperidol, halothane, ketamine, morphine, nitrous oxide, pethidine, phenoperidine, prilocaine and propanidid. It is suggested that those anaesthetic agents which induced activity of the enzyme should not be administered to patients with an acute porphyria.