Cystine aminopeptidase (oxytocinase) activity in plasma and tissues of normal and infected pregnant cattle.

Cystine aminopeptidase (CAP) activity in tissues and in plasma from pregnant cows was measured at various stages of gestation by using the substrate S-benzyl-L-cysteine-4-nitroanilide. The CAP activity was as high or higher in hepatic and renal tissues as in cotyledonary tissue. Plasma CAP activity was low and did not change with length of gestation, nor did it change when placentation was disrupted by infection with Aspergillus fumigatus.