A putative role for cell-cell epithelial contacts in lactose secretion

Rates of synthesis and secretory release and the maximal requisite intracellular transit time (Tsec) for lactose were measured in vitro for three preparations of lactating guinea pig mammary tissue: tissue slices, mammary epithelial cell (MEC) acini, and mono-dispersed MEC. The Tsec values for tissue slice and acini preparations were similar, lactose required approximately 16 min to pass from its site of synthesis (Golgi) to the extracellular medium. Dispersal of mammary tissue into single cells by collagenase disruption of all cell-cell junctional complexes increased the Tsec value to approximately 25 min but did not alter kinetics of lactose synthesis and secretory release. These data suggest a possible involvement of cell-cell junctional contacts in intracellular transport of lactose.