Protein and glucose-induced changes in sodium transport across the pig small intestine.

1. The effect of glucose and of bovine gamma-globulin on short-circuit current and sodium transport was measured using new-born pig ileum before and after suckling.2. Glucose increased the short-circuit current with an apparent K(m) of 1.9 and 19.5 mM for new-born unsuckled and suckled intestines respectively. The V(max) was about 80 muA cm(-2) in each case.3. Bovine gamma-globulin applied to new-born pig ileum caused a 20% increase in sodium chloride influx without change of short-circuit current. The tissue conductance was also greater in the presence of globulin. These effects were not seen in ileum taken from suckled pigs.4. p-Chloromercuriphenyl sulphonic acid (PCMPS) inhibited the globulin induced increase in sodium influx in new-born pig ileum without changing the measured short-circuit current. 0.1 mM-PCMPS also changed the characteristics of the glucose-dependent increase in short-circuit current, so that this response came to resemble that seen in ileum taken from suckled pigs. Dithioerythritol reversed this effect of PCMPS.5. The suckling-dependent difference in results is explained in terms of a change in microvillar function taking place as a consequence of long-term pinocytosis in vivo. The ability of PCMPS to simulate some of these changes suggests that sulphydryl groups might be important regulators of microvillar membrane stability.