In vitro absorption of gamma-globulin by neonatal intestinal epithelium of the pig.

1. An in vitro method, using fluorescent gamma-globulin and everted neonatal pig's intestinal slices, for the study of the active transport of large molecules is described.2. Uptake of gamma-globulin occurred within 15 min and required no exogenous substrates.3. In vitro absorption of gamma-globulin by intestinal epithelium was limited to the neonatal pig and 5-day-old mouse. No uptake was seen in intestines from a mature mouse, a pig with diarrhoea, a normal pig, a mature rabbit, a guinea-pig, a chick, and a chick embryo. Chick embryo yolk sac readily took up gamma-globulin.4. Rings of everted intestinal epithelium remained active (still absorbed gamma-globulin) after incubating for 4-6 hr in balanced salt solution (BSS).5. Uptake of gamma-globulin required oxygen and sodium and was reversibly inhibited by metabolic antagonists such as iodoacetate, arsenate, fluoride, 4,6-dinitro-varphi-cresol, phlorrhizin, anaerobiosis and cold. Under the conditions of the test, large colloidal molecules did not inhibit uptake of gamma-globulin.6. Similar results (although not as clear-cut) with metabolic inhibitors were obtained with preparations of chick embryo yolk sacs.7. Injuring mature pig's intestinal epithelium with surface-active agents did not produce non-specific absorption artifacts that resembled the specific absorption found in immature pig's intestinal epithelium.