No abstract

Several reports have shown the apparent superiority of NaCl solution over water as a lymphagogue; most of these studies have been carried out in ad libitum drinking animals (1). We have studied the effect of triglycerides, starch, casein, hormones, and Na+/K+ ratio on lymph flow. These studies were made possible by the development of a modified Bollman's technique for the cannulation of the abdominal thoracic duct in the rat (2), which includes the infusion of solutions into the duodenum at a constant rate to assure a uniform lymph flow rate. The substances listed above and found to be lymphagogic, with the exception of triglycerides, were only effective when the animals were infused with 0.85% NaCl solution rather than with water.Materials and Methods. Female rats (300 t_ 15 g) were purchased from Charles River Breeding Labs. (North Wilmington, Mass.) and were fed Purina chow. The surgical technique for the cannulation of the abdominal thoracic duct has been described in detail ( 2 ) . In the present studies, cannulation of the thoracic duct was followed by cannulation of the avascular part of the stomach. After operation, the animal was put in a restraining cage; the catheter going into the stomach was connected to a compact infusion pump, model 975 (Harvard Apparatus Co., Inc., Dover, Mass.). A container covered with a wire gauze was placed underneath the animal to collect the excreta and to separate the feces from the urine. The latter was then measured during variable intervals c o r r e c spondinp to the periods of lymph cdlectio~,! 1 Throughout these studies a constant $fusion rate of 4 ml/h was used. The variables investigated were: concentration of NaCl, the effect of various ratios of 0.85% NaCl and 0.85% KCI, of 2% protein, of 1-2076 carbohydrate, and of 2% triglycerides in either saline or water. In addition, subcutaneous injections of vasopressin (p-hypophamine) , oxytocin (a-hypophamine) or deoxycorticosterone (Doca) were studied during the infusion of either 0.851% saline or water in these stomach fistula-thoracic duct fistula animals.Results. As shown in Fig.

Unanesthetized rats with catheterized portal veins were administered, intragastrically, a saline solution of the diketopiperazine cyclo(L-leucyl-[U-14C]glycine) (cyclo(L-Leu-[14C]Gly)) at a dose of 47.9 nmol. The appearance of this cyclic dipeptide in portal vein plasma was followed chromatographically using a microcolumn of Sephadex G-25 complexed with copper. Further identification was done by thin-layer chromatography. Net absorption was evaluated by the balance method. The intestinal site of maximal absorptive capacity for cyclo(L-Leu-[14C]Gly) was also investigated. The gastric emptying rate was 98% in 15 min. After intragastric administration, cyclo(L-Leu-[14C]Gly) was absorbed (peak at 2.5 min) into the portal vein. The balance method showed that the efficiency of absorption was 94% within the first 10 min and was completed after 20 min. This compound was absorbed intact and remained unmetabolized in the portal vein of the rat and seemed to be absorbed throughout the length of the small intestine. Shortly after administration (1- to 5-min period), the greatest absorption of the diketopiperazine occurred at the level of the duodenum; however, the absorption maximum appeared to move down the gut and after 10 min the highest uptake took place in the jejunum, but never seemed to reach the ileum to a significant degree. Only negligible amounts of the cyclic dipeptide were excreted with the feces. Cyclo(L-Leu-[14C]Gly) is thus an example of a low molecular weight peptide which is rapidly and completely absorbed, after its intragastric administration at low concentration and is enzymatically stable during the process of absorption. In vitro experiments determined that this peptide apparently traverses the intestinal wall passively and does not use the carrier-mediated mechanisms for linear peptides.