Normal serum albumin transfer from blood to small intestine and its role in albumin breakdown.

131I-albumin transfer into isolated segments of the small intestine has been determined following the intravenous injection of human 131I-albumin in 23 dogs. The importance of different intestinal segments in the normal degradation of albumin has been established. The slope of the serum disappearance curve was unaltered with proves that the applied technique had no damaging effect. Albumin leakage was not uniform in the whole length of the small intestine. It was highest in the duodenum (0.241 +/- 0.014 ml/10 cm intestine/hour). This was followed by the jejunum (0.142 +/- 0.022 ml/10 cm intestine/hour), and the smallest vally quantity of albumin leakage corresponded to a plasma volume of 14.49 ml in the duodenum, 27.16 ml in the jejunum, and to 23.76 ml in the ileum. The relationship of albumin leakage and catabolism revealed that protein bound activity (transferred and regained) in the dudodenum, in spite of the shortness of this section of the intestine, was responsible for 11.72 +/- 1.70% of total catabolism, that in the jejunum for 21.28 +/- 3.69%, and that in the ileum for 19.24 +/- 3.64%. The sum of the catabolism of the three intestinal segments yielded 52.26 +/- 6.65% of the total catabolism. After correction with a proteolytic factor, this value was 68.44%. Our examinations have established that the small intestine is the main region of normal albumin breakdown.