Incorporation of [14C]glucose into lactose and neuramin-lactose by rat mammary glands

Incubation of rat-mammary-gland slices in a physiological solution containing [¹⁴C]glucose disclosed incorporation of radioactivity into both lactose and neuraminlactose. After 1 min incubation the labeling was restricted to the glucose moiety of these molecules while administering the glucose in vivo resulted in labeling of all components of these molecules after 3 h.

The specific activities of free lactose and lactose from neuramin-lactose are of similar order of magnitude in all experiments and, although these findings are compatible with the currently known biosynthetic pathways of these substances, the possibility of an alternate pathway involving the action of neuraminidase is suggested in connection with the rapid equilibration of the specific activities of these substances.