Ribonuclease activity in the rat mammary gland during pregnancy, lactation and mammary involution

Abstract

The enzymic breakdown of ribonucleic acid by suspensions of rat mammary gland has been investigated. The variation in enzyme activity with pH indicated the presence of an acid (pH optimum 5-8) and an alkaline (pH optimum 8-0) enzyme. The activities of both acid and alkaline ribonu-cleases have been studied at six stages in the lactation cycle: in the virgin animal, in late pregnancy, in early and in late lactation, and at 2 and 4 days of involution. Both acid and alkaline ribonucleases increased during pregnancy, over parturition and during lactation. The acid ribonuclease decreased only slightly in early involution; alkaline ribonuclease decreased approximately threefold by the fourth day of mammary involution.