The absorption of polyvinyl pyrrolidone by the new-born pig intestine.

1. The intestinal absorption of [(131)I]polyvinyl pyrrolidone of mean mol. wt. 160,000 (K. 60) and 40,000 (K. 30) after oral administration has been measured in unsuckled conscious pigs less than 20 hr old. Absorption was assessed by the measurement of the concentration of [(131)I]PVP in venous blood during the 6 hr after feeding and also by the distribution at the end of the experiment of [(131)I]PVP between homogenates of the alimentary tract and homogenates of the rest of the animal.2. The concentration of [(131)I]PVP in the peripheral blood after feeding was dependent upon the mol. wt. of the polymer, when comparable amounts had been absorbed from the intestine. PVP K. 60 attained higher blood concentrations than PVP K. 30 and the blood concentrations of PVP K. 60 were close to the values to be expected if all the material which had left the intestine had remained in the blood. The lower blood concentrations found when PVP K. 30 was fed were associated with the disappearance of labelled solute from the gut and were thus the consequence of the relatively rapid escape of labelled solute from the plasma after absorption had taken place.3. The ability of the intestine to absorb [(131)I]PVP K. 60 declined progressively after birth but did not terminate abruptly unless the animal was fed colostrum. In unsuckled animals the rate and extent of absorption at 3 hr was much greater than at 20 hr after birth, but some absorption was still present at least 65 hr after birth.4. The transfer of PVP K. 60 to the peripheral blood was dependent upon factors in sow colostrum, since significant absorption did not occur when PVP was fed in water or simple salt solutions.5. The factors which accelerated absorption were present in colostrum from the goat, cow and ewe as well as that from the sow; they remained in the whey, but, in contrast to the factors which accelerate absorption in the calf, were largely inactivated by boiling. Similarly, neither phosphate, lactate, pyruvate, nor lower volatile fatty acid salts, which were effective in the calf, accelerated absorption in the pig.6. The absorption of [(131)I]PVP K. 30 was found to be much less dependent upon the composition of the solvent than the absorption of [(131)I]PVP K. 60, although absorption was most rapid when PVP K. 30 was fed in colostrum.