HSA production by mammary explants of virgin transgenic mice: A reliable tool for predicting levels of secretion into milk

Abstract

SUMMARY Lactating females of eight independent strains of transgenic mice carrying a human serum albumin (HSA) gene or minigene under the control of the Blactoglobulin (BLG) promoter secrete strain-specific amounts of HSA into their milk, ranging from 0-4.5 mg per ml. The HSA produced in the milk of all transgenic strains appeared to be identical. The ability of mammary explants from virgin females of these strains to de novo synthesize and secrete HSA immediately upon explantation, or on day 5 of culture in the presence of insulin and prolactin, was evaluated based upon total de novo protein synthesis as well as equal tissue weight. Levels of de novo HSA synthesis and secretion by explants were compared with levels of secretion of HSA in the milk of lactating females of these same strains. The correlation of relative densitometric values of HSA production in vivo versus in vitro ranged from r=0.70 to r=0.92. In all cases, correlation improved when explants were cultured for 5 days in the presence of hormones compared to explants evaluated immediately upon explantation.