Metabolic energy and cytoskeletal requirements for synthesis and secretion by acini from rat mammary gland-II. Intracellular transport and secretion of protein and lactose.

1. Iodoacetate, 2,4-dinitrophenol, cyanide and cycloheximide inhibited protein secretion as well as synthesis by acini (alveoli) from rat mammary gland. Cytochalasin B and vinblastine inhibited protein secretion and marginally reduced protein synthesis. Colchicine was without effect on protein synthesis but inhibited secretion. 2. Intracellular protein transport was altered during incubation with metabolic and cytoskeletal inhibitors. Cycloheximide, iodoacetate. 2,4-dinitrophenol and cytochalasin B appeared to block protein synthesis on polysomes of rough endoplasmic reticulum. Vinblastine inhibited protein transport from rough endoplasmic reticulum to Golgi apparatus and colchicine appeared to cause accumulation of protein in several endomembrane fractions. 3. Iodoacetate reduced acinar lactose content but was without effect on lactose synthetase activity. Cyanide, cycloheximide and vinblastine reduced reduced lactose synthetase activity but not tissue lactose concentration. Cytochalasin B reduced glucose incorporation but was without effect on lactose content and lactose synthetase activity. Colchicine and 2,4-dinitrophenol did not alter glucose incorporation, lactose content or lactose synthetase activity. Lactose secretion was inhibited by all metabolic and cytoskeletal inhibitors examined. 4. Results indicated that sustained protein secretion depended on continued protein synthesis and that lactose secretion was coupled to protein secretion.