RESUMO
The regulation of beta-1,3 galactosyltransferase (3betaGalT) and beta-1,4 galactosyltransferase enzymatic (4betaGalT) activities in the mammary gland of the tammar wallaby (Macropus eugenii) have been characterised. These two beta-galactosyltransferases are active at different times during the lactation cycle and play a central role in regulating the carbohydrate composition in tammar milk, which changes progressively throughout lactation to assist the physiological development of the altrical young. The 4betaGalT activity was present at parturition and increased 3-fold by day 10 of lactation (d10L), whereas 3betaGalT activity was barely detectable at day d5L and then increased 6-fold by d10L. This increase in activity of both enzymes was sucking dependent. While 3betaGalT activity was not observed in the mammary gland prior to d7L, this activity was found in mammary explants from late pregnant tammar cultured with insulin, hydrocortisone and prolactin (IFP) and was further stimulated by the addition of tri-iodothyronine (T) and 17beta-oestradiol (E). The activity of 4betaGalT in these explants was stimulated maximally with IFP. These data suggest the temporal activity of both 3betaGalT and 4betaGalT is most likely regulated by both endocrine stimuli and factors intrinsic to the mammary gland.
