Catabolism of neurotensin in interstitial fluid of the rat stomach

Abstract

The catabolism of neurotensin (NT) was studied in the gastric submucosa of the conscious rat using a novel technique to obtain a dialysate of interstitial fluid. A microdialysis fiber system was surgically implanted into the gastric submucosa, and 2 days later experiments were commenced on conscious animals. Isotope-labeled NT was administered to the tissue, and a dialysate of the submucosal interstitial fluid was collected. In the dialysate, NT and catabolites of NT formed in the interstitial fluid were identified and quantitated by high-pressure liquid chromatography. The catabolism of 125I-NT-(1-13) and [3H]NT-(1-13) was studied as was the further breakdown of the major catabolites. NT-(1-13) was, regardless of the type of label, catabolized mainly into NT-(1-8), NT-(9-13), NT-(1-11), and free tyrosine. None of the catabolites formed is known to possess significant biological activity. NT-(9-13) was rapidly cleared, whereas the amino-terminal fragments NT-(1-8) and NT-(1-11) were more resistant to degradation. The biological half-life of neurotensin in the gastric submucosa of the rat was between 9 and 15 min.

Metabolism and potency of xenin and of its reduced hexapseudopeptide Ψ fragment in the dog

“…An analogous C-terminal octapeptide fragment of the related peptide neurotensin has not been described, when the metabolic break-down fragments of neurotensin were investigated in several species in vitro and in vivo (Shulkes et al, 1983;Bunnett et al, 1984;Lee et al, 1984;Shaw et al, 1987;Holst Pedersen et al, 1980;Barelli et al, 1994;Mentlein and Dahms, 1994).…”

Post‐translational Modification of Peptide Messengers in the Gut

“…A novel method for the study of peptide catabolism in interstitial fluid has been used in which hollow dialysis fibres attached at both ends to infusion tubing, were implanted in the gastric submucosa. Perfusion of the dialysis fibres with a non-diffusible protein solution permitted osmotic dialysis of endogenous, or exogenously administered molecules such as peptides and their metabolites, from the interstitial fluid (Bunnett, Walsh, Debas, Kauffman & Golanska, 1983;Bunnett, Mogard, Orloff, Corbet, Reeve & Walsh, 1984). This technique has been used to define the degradation patterns of exogenously administered radiolabelled neurotensin in the rat gastric submucosa (Bunnett et al 1984).…”

“…Perfusion of the dialysis fibres with a non-diffusible protein solution permitted osmotic dialysis of endogenous, or exogenously administered molecules such as peptides and their metabolites, from the interstitial fluid (Bunnett, Walsh, Debas, Kauffman & Golanska, 1983;Bunnett, Mogard, Orloff, Corbet, Reeve & Walsh, 1984). This technique has been used to define the degradation patterns of exogenously administered radiolabelled neurotensin in the rat gastric submucosa (Bunnett et al 1984). However, collection of interstitial fluid and analysis of endogenous peptide metabolites cannot determine to what extent the neuropeptides were processed post-secretion and before receptor occupancy or after they had exerted their biological effects.…”