title: Effect of milk on somatostatin degradation in suckling rat jejunum in vivo.
abstract: BACKGROUND
  Somatostatin-14 is present in breast milk, and intact somatostatin-14 has been recovered from gastric lumen of infants. Studies have shown that somatostatin-14 is metabolized in the intestinal luminal contents in vitro, which could be prevented by the presence of breast milk. In this study, the effect of milk on stability of somatostatin-14 in suckling rat jejunum in vivo was examined.
  
  
  METHODS
  125I-Somatostatin-14[Tyr 11] was administered to the isolated jejunal loops in anesthetized suckling rats in the absence or presence of milk, fractions of milk, or known protease-peptidase inhibitors. Structural integrity of 125I-somatostatin-14[Tyr 11] recovered from tissues at different intervals was analyzed by gel filtration and high-performance liquid chromatography.
  
  
  RESULTS
  Radioactivity rapidly disappeared from the jejunal lumen with a 50% clearance achieved by 1.2 minutes. Gel filtration and high-performance liquid chromatography analyses showed that 125I-somatostatin- 14[Tyr 11] was rapidly degraded into smaller fragments. At 1 minute, jejunal luminal radioactivity was eluted in a major peak with retention time of 42.4 minutes, along with other minor peaks (retention time, 5.6, 8.0, 10.4, and 14.4 minutes); only a trace amount of intact 125I-somatostatin-14[Tyr 11] (retention time, 44.8 minutes) was present. Coadministration of rat's milk or its soluble fraction increased the level of intact 125I-somatostatin-14[Tyr 11] in the jejunal lumen and jejunal tissue. Presence of rat's milk-casein or peptidase inhibitors (bestatin, phosphoramidon, or Bowman-Birk inhibitor), however, failed to increase the level of intact 125I-somatostatin-14[Tyr 11].
  
  
  CONCLUSIONS
  These results suggest that somatostatin-14 is rapidly degraded in the jejunal lumen of suckling rats, and that milk-borne peptidase inhibitors prevent this somatostatin-14 degradation.
authors.affiliation: Department of Pharmacology, University of Arizona Health Sciences Center, Tucson, USA.
authors.forename: R K
authors.initials: RK
authors.lastname: Rao
authors.forename: T P
authors.initials: TP
authors.lastname: Davis
authors.forename: C
authors.initials: C
authors.lastname: Williams
authors.forename: O
authors.initials: O
authors.lastname: Koldovsky
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D002851:Chromatography, High Pressure Liquid; D005260:Female; D007457:Iodine Radioisotopes; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008892:Milk; D011480:Protease Inhibitors / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013004:Somatostatin / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D011480:Protease Inhibitors; D013004:Somatostatin