Intestinal Assimilation of Intact Peptides and Proteins From the Diet‐a Neglected Field?

Gardner, Michael L. G.

doi:10.1111/j.1469-185x.1984.tb00708.x

Cited by 117 publications

(49 citation statements)

References 194 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…4A). This is in agreement with the observations of Menzies (1974, 1984), Wheeler et al (1978 and Maxton, Bjarnason, Reynolds, Catt, Peters & Menzies (1986), and is probably due to enhancement of paracellular permeability via the 'tight' junctions. Temporary cellular shrinkage might be responsible.…”

Section: L G Gardner and Otherssupporting

confidence: 82%

“…However, it is commonly assumed that peptides absorbed via these mechanisms are hydrolysed in the epithelial cytosol so that only free amino acids enter the circulation. Much evidence suggests that this MS 8788 view is incorrect (Gardner, 1984;Gardner & Wood, 1989), but it has hitherto been impossible to obtain reliable estimates of the total amounts of intact peptides that enter the circulation during assimilation of protein. This assumes special significance since (i) biologically active peptides can be produced experimentally by peptic digestion of dietary proteins (e.g.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Intestinal absorption of the intact peptide carnosine in man, and comparison with intestinal permeability to lactulose.

Gardner

Illingworth

Kelleher

et al. 1991

The Journal of Physiology

142

107

View full text Add to dashboard Cite

SUMMARY Healthy humans ingested the dipeptide carnosine (L-/I-alanyl-L-histidine).Their plasma levels and urinary outputs of carnosine and ,8-alanine were monitored over the following 5 h.2. Large amounts of intact carnosine (up to 14 % of the ingested dose) were recovered in the urine over the 5 h after ingestion. However, carnosine was undetectable in the plasma unless precautions were taken to inhibit blood carnosinase activity ex vivo during and after blood collection.3. The amount of carnosine recovered in urine varied substantially between subjects. It correlated negatively with carnosinase enzymic activity in the plasma. Highest carnosinase activities were observed in those subjects who regularly underwent physical training.4. Urinary recovery of the disaccharide lactulose also varied considerably between subjects, but was substantially lower than that of carnosine. There was no significant correlation between the recoveries of carnosine and lactulose. 5. When lactulose was ingested with a hypertonic solution, the urinary recovery of lactulose was generally increased. When carnosine was ingested with a hypertonic solution, the urinary recovery of carnosine was reduced: hence the paracellular route probably is not dominant for absorption of intact carnosine.6. Intact carnosine must have crossed the intestine to an extent much greater than hitherto recognized. Rapid post-absorptive hydrolysis is a severe obstacle to quantification of intact peptide absorption.

show abstract

Section: L G Gardner and Otherssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Intestinal absorption of the intact peptide carnosine in man, and comparison with intestinal permeability to lactulose.

Gardner

Illingworth

Kelleher

et al. 1991

The Journal of Physiology

142

107

View full text Add to dashboard Cite

show abstract

“…It cannot be excluded, that such oligopeptides may also be recognised by one of the physiological peptide carriers, which have been described for dipeptides, tri-or tetrapeptides. For those peptides pH-dependent absorption systems are discussed (Gardner, 1984;Humphrey & Ringrose, 1986;Tsuji et al, 1987;Wilson et al, 1989), whereas our experiments suggest a Na+-dependent or potential-dependent mechanism for the uptake of octreotide. The observed Na+-dependency may be an indirect effect via the Na+/H '-exchange system by producing a proton gradient as previously discussed for dipeptides (Ganapathy et al, 1984).…”

Section: Discussioncontrasting

confidence: 49%

Enteral absorption of octreotide

Fricker

Drewe

Vonderscher

et al. 1992

British J Pharmacology

View full text Add to dashboard Cite

1 The somatostatin octapeptide-analogue, octreotide, is absorbed as intact peptide from the gastrointestinal (GI) tract. 2 In situ absorption experiments in rats confirmed our recent intubation studies in human volunteers demonstrating that the peptide has preferential absorption sites in the small intestine. Absorption of octreotide was higher in the jejunum than in the duodenum or the ileum. 3 Experiments with bile-duct cannulated rats demonstrated that the absorption of octreotide decreased in the presence of bile, reflecting a negative influence of biliary components on the absorption of the peptide. 4 Uptake experiments using rat jejunal brush border membranes were performed to analyse the absorption mechanisms. The transport of octreotide into jejunal brush border membranes was significantly higher than the uptake into membrane vesicles isolated from rat ileum. When initial uptake (0-15 s) rates into the membrane vesicles were calculated as a function of the peptide concentration, a saturable component could be observed, indicative of transport mechanisms different from simple diffusion.

show abstract

“…The X-Pro type dipeptides released by ACE are not readily hydrolyzed by brush border membrane peptidases and are probably absorbed intact (22,23). It has been shown that amino acids are more efficiently absorbed in peptide form when compared to free amino acid (17,24,25). Therefore, the fact that the COOHterminal dipeptides are the major hydrolytic products from these proline-containing peptides indicates that they have an advantage in being efficiently absorbed by the intestinal mucosa.…”

Section: Resultsmentioning

confidence: 99%

Digestion and assimilation of proline-containing peptides by rat intestinal brush border membrane carboxypeptidases. Role of the combined action of angiotensin-converting enzyme and carboxypeptidase P.

Yoshioka¹,

Erickson²,

Kim³

1988

J. Clin. Invest.

View full text Add to dashboard Cite

Two intestinal brush border membrane carboxypeptidases were found to participate in the sequential digestion of proline-containing peptides representing a novel mechanism of hydrolysis from the COOH terminus. NH2-blocked prolyl tripeptides were rapidly hydrolyzed by either brush border membrane angiotensin converting enzyme (ACE, dipeptidyl carboxypeptidase, E.C. 3.4.15.1) or carboxypeptidase P (E.C3.4.12-) depending on the position of the proline residue. Furthermore, these two enzymes were found to participate in a concerted manner to sequentially degrade larger proline-containing pentapeptides from the COOH terminus. A brush border membrane associated neutral endopeptidase also participated in the hydrolysis of the prolyl pentapeptides.During in vivo intestinal perfusion, the NH2-blocked prolyl peptides were degraded and their constituent amino acids efficiently absorbed by the intestine. Furthermore, hydrolysis and absorption of these peptides could be dramatically suppressed by low concentrations of captopril, a specific inhibitor of ACE.These studies show that prolyl peptides are efficiently and sequentially hydrolyzed from the COOH terminus by the combined action of ACE and carboxypeptidase P, and that these enzymes may play an important role in the digestion and assimilation of proline-containing peptides.

show abstract

Intestinal Assimilation of Intact Peptides and Proteins From the Diet‐a Neglected Field?

Cited by 117 publications

References 194 publications

Intestinal absorption of the intact peptide carnosine in man, and comparison with intestinal permeability to lactulose.

Intestinal absorption of the intact peptide carnosine in man, and comparison with intestinal permeability to lactulose.

Enteral absorption of octreotide

Digestion and assimilation of proline-containing peptides by rat intestinal brush border membrane carboxypeptidases. Role of the combined action of angiotensin-converting enzyme and carboxypeptidase P.

Contact Info

Product

Resources

About