Development of a chronic canine model for measurement of absorption by substrate appearance in portal venous blood

Comparison of cyclosporin A absorption from LCT and MCT solutions following intrajejunal administration in conscious dogs

Absorption from the intestine of cyclosporin A (CsA), dissolved in either a medium-chain (MCT) or a long-chain triglyceride (LCT) solution, was investigated in a chronic dog model. Following intrajejunal administration of 20 mg of CsA/kg of body weight, absorption, judged by the portalvenous appearance of CsA, was determined by measuring whole blood CsA concentrations in the portalvenous and arterial blood and the portalvenous flow. Appearance of CsA from LCT commenced earlier and attained significantly higher mean peak values (+/- SEM) in the portalvenous blood (2557 +/- 436 ng/mL) than from MCT (274 +/- 80 ng/mL). Portalvenous concentrations of CsA were always higher than arterial concentrations for both LCT and MCT, suggesting that CsA is transported by portalvenous blood following uptake from the gut. Absorption of CsA, measured over 300 min, was 10 times higher with LCT (9.96 +/- 2.00%) than with MCT (0.95 +/- 0.21%). This significant difference is believed to result from the formation of mixed micelles which occurs during digestion of LCT but not MCT.

Free and conjugated catecholamines and serotonin in canine thoracic duct lymph: effects of feeding

The source and fate of sulfoconjugated catecholamines present in plasma are not known. Sulfated norepinephrine has been shown to overflow together with free norepinephrine from a typical peripheral neuroeffector junction. Some released free norepinephrine is removed via the lymphatic system, but it is not known whether sulfated catecholamines are removed similarly. Serotonin, another biogenic amine, is released from the enterochromaffin cells into portal blood. The aims of the present study were to determine whether conjugated catecholamines and serotonin could be detected in thoracic duct lymph of dogs and to compare concentrations in lymph with those in samples of portal blood collected before and after the dogs were fed. A method is described for the extraction and purification of free and conjugated catecholamines and serotonin from lymph. In lymph and in plasma, there were similar concentrations of free (0.2-0.4 ng/ml) and conjugated (0.1-0.2 ng/ml) norepinephrine and of conjugated dopamine (0.2-1.0 ng/ml). The concentrations of free serotonin were much lower in lymph (0.1-0.2 ng/ml) than in portal blood (100-200 ng/ml). Small amounts of conjugated serotonin (0.1-0.4 ng/ml) were detected in lymph but were not detected in plasma. Feeding caused increases in concentration of conjugated dopamine in lymph and in plasma and small increases in the output of free norepinephrine and free and conjugated serotonin in lymph.

Absorption of protein in the early postoperative period in chronic conscious dogs

Postoperative alterations in amino acid exchange across the intestinal tract and in the capacity for protein absorption were investigated in a chronic canine model. Changes in postoperative splanchnic amino acid exchange consisted of a temporary decrease of total splanchnic amino acid release, including a significant reduction in alanine production, and an increase in glutamine consumption. Contrary to results under stable metabolic conditions, branched chain amino acids were also taken up by the intestine in the early postoperative period. The changes in postoperative amino acid exchange were not, however, reflected by a corresponding alteration in protein transport capacity. The absorptive capacity for a protein hydrolysate remained stable during the early postoperative period.