in'the RatafterCefazolinTreatment

Treatment of rats with cefazolin in vivo significantly suppressed activity of alanine and aspartate aminotransferases in serum and in the liver, brain, kidney, and heart. Simultaneousadministration of pyridoxal further reduced enzyme activity except in the liver, where there was no change. Pyridoxal 5’-phosphate partly reversed the decreased enzyme activity in the serum, liver, and kidney, but did not return it to the amount observed in the control animals;enzymeactivity remainedsuppressedin the brain and heart. The effect of cefazolin was dose related, but there was no sex-relateddifference. Incontrastto itsaction on aminotransferase activity, cefazolin elicited no effect on alkaline phosphatase (pyridoxal-5’-phosphate hydrolase) in serum or on pyruvate carboxylase in the liver, heart, and kidney. Cefazolin exposed to the hepatic microsomalmixed-functionoxidasesystemin vitro was partly converted into metabolites that inhibited serum alanine aminotransferaseactivity in vitro. The latter inhibitionwas reversed by the addition of pyridoxal 5’-phosphate.