Glycine Absorption Research Articles

Small intestinal absorption of amino acids and a dipeptide in pancreatic insufficiency.

In this study a perfusion technique has been used to investigate in vivo jejunal absorption and transmural potential difference evoked by the neutral amino acids phenylalanine (56 or 20 mmol/l) and glycine (20 mmol/l), the dibasic amino acid lysine (56 or 5 mmol/l), and a dipeptide glycyl-l-phenylalanine (20 mmol/l) in 11 children with pancreatic insufficiency due to cystic fibrosis and in three children with other causes of exocrine pancreatic insufficiency. Net absorption and potential difference evoked by phenylalanine in both cystic fibrosis and pancreatic insufficiency, and net absorption of glycine in cystic fibrosis were significantly reduced; but the absorption of lysine and glycyl-l-phenylalanine was normal. Absorption of the constituent amino acids from the dipeptide was normal or increased in cystic fibrosis. Thus, these studies show a defect in active absorption of neutral amino acids in cystic fibrosis with pancreatic insufficiency and exocrine pancreatic insufficiency. We speculate that pancreatic factors participate in neutral amino acid absorption.

Postprandial plasma concentrations of glycine and taurine conjugated bile acids in healthy subjects.

Fasting and postprandial plasma concentrations of glycine and taurine conjugates of cholic, chenodeoxycholic, and deoxycholic acid were measured by a high pressure liquid chromatography-enzymatic assay in nine healthy subjects. The mean value of each bile acid concentration increased significantly (2.4-4.7 times) in the postprandial period. The total glycine taurine ratio of 2.5 in the fasting state increased significantly to a maximum value of 3.3 at one to 1 1/2 hours postprandially and then declined. This shift in glycine taurine ratio shows, that the relative increase in concentrations of glycine conjugates exceeds the relative increase in concentrations of taurine conjugates in the early postprandial period, and supports the view that there is significant absorption of glycine conjugated bile acids from the proximal small intestine.

Small intestinal absorption of glycine and glycyl-glycine in patients with chronic renal failure.

Intestinal absorption of glycine and glycyl-glycine was studied in 9 patients with chronic renal insufficiency (mean creatinine clearance 9 ml/min) and 7 healthy controls. After an oral load of the amino acid or dipeptide, plasma alpha-amino nitrogen (alpha-NH2N) was measured repeatedly for two hours and the area under curve (AUC) was calculated using the trapezoidal rule. In uremic patients, plasma alpha-NH2N was significantly lower after glycine than after glycyl-glycine at 30, 45 and 60 min and also AUC was smaller after the amino acid indicating a reduced total uptake. One patient with severe, terminal uremia had a flat curve after glycine administration. In control subjects, plasma levels were lower after glycine than after glycyl-glycine at 30 min but AUC did not differ between the amino acid and the dipeptide. Generally these results agree with those in earlier studies of non-uremic man showing that, in small intestine, dipeptides are taken up better and by a different mechanism than amino acids.

Effect of mercuric chloride on the intestinal absorption of an amino acid, glycine, in the freshwater murrel, Channa punctatus

The effect of five concentrations of mercuric chloride (10 mM, 1 mM, 0.1 mM, 0.01 mM, 0.001 mM) on the rate of absorption of the amino acid glycine by the intestine of the freshwater murrel Charma punctatus has been studied. Intestinal absorption of glycine was also studied in fish exposed to a sublethal concentration (3 μg/l) of mercuric chloride for 15 and 30 days. The results revealed that all the five concentrations of mercuric chloride reduced the rate of absorption of glycine by the intestine. Maximum decrease was recorded with 10 mM of mercuric chloride in the instilled medium. The reduction in glycine transport was insignificant with 0.01 and 0.001 mM of mercuric chloride. In fish exposed to mercuric chloride by bath also, decrease in the rate of absorption of glycine was noted but it was significant only after 30 days of exposure.

Glycine absorption in rats infected with Eimeria nieschulzi

Glycine absorption in rats infected with Eimeria nieschulzi

Stimulation of gastric acid secreted by glycine and related oligopeptides in humans.

To investigate the effect of oligopeptides on gastric secretion in humans, we investigated acid secretion in healthy volunteers after the intragastric infusion of physiological saline, glycine (100 mM), diglycine (50 mM), triglycine (33 mM), and tetraglycine (25 mM). All test solutions were equivalent in glycine content, osmolality (300 mosmol), and pH (5.5). Although the rate of acid secretion was greater during glycine than saline infusion [5.6 +/- 0.8 vs. 3.3 +/- 1.1 mmol/h (means +/- SE); P less than 0.05], the rate of acid secretion during glycine infusion was not significantly different from that induced by its related peptides. There were increases in plasma glycine concentration during infusion of glycine and its related peptides but no detectable changes in serum gastrin levels. The increases in plasma glycine must have been due to absorption from the small intestine because there was no gastric absorption of glycine in free or dipeptide form nor diglycine hydrolysis in the stomach. Therefore, our results permit implicating only the increased plasma glycine concentrations as the stimulus for acid secretion by glycine and its homologous peptides.

Alterations in intestinal function in response to thyroxine and cortisone administration in undernourished rats.

Imposition of undernutrition during the suckling period considerably enhanced the intestinal uptake of D-glucose and glycine compared to a control group. Brush border sucrase, and alkaline phosphatase activities were drastically reduced while lactase and leucine amino peptidase levels were significantly elevated at weaning in nutritionally deprived pups as compared to control animals. Cortisone administration to undernourished rats depressed the uptake of D-glucose but stimulated that of glycine. Thyroxine treatment to undernourished animals reduced the uptake of glucose but had no effect on glycine absorption. Brush border sucrase and alkaline phosphatase activities were stimulated in cortisone- or thyroxine-injected undernourished rats but lactase activity was depressed under these conditions. Leucine aminopeptidase activity remained unaffected in cortisone- or thyroxine-administered undernourished pups.

Mercury induced alterations in the intestinal, absorption of nutrients in the fresh water murrel, [formula omitted][formula omitted

The effect of five concentrations (10 mM, 1 mM, 0.1 mM, 0.01 mM and 0.001 mM) of mercury on the rate of absorption of glucose, fructose, glycine and tryptophan by the intestine of the fresh water murrel Channa punctatus has been studied. Intestinal absorption of these nutrients was also examined in fish exposed to a sublethal concentration (3 μg/l) of mercury for 15 and 30 days. Significant decrease was recorded in the rate of intestinal absorption of all the four nutrients with higher concentrations (10 mM, 1 mM and 0.1 mM) of mercury. 0.01 mM and 0.001 mM of mercury also reduced the transport rate but it was insignificant, except in case of tryptophan, where 0.01 mM of mercury also produced significant decrease. Exposure of fish by bath to mercury also resulted in significant decrease in the intestinal transport rate of all the four nutrients after 30 days.

Problems associated with the use of cycloheximide to distinguish between animal drug residues bound to protein and those incorporated into protein

The use of cycloheximide to distinguish between covalently-bound drug residues in animals and residues due to the incorporation of drug fragments into endogenous molecules was explored. The results indicated that cycloheximide prevented the absorption of both glycine and ronidazole from the gastro-intestinal tract, an effect that complicates its use in the characterization of drug residues in animals.

A Study of In Vivo Glycine Absorption by Fed and Fasted Rainbow Trout (Salmo Gairdneri)

ABSTRACT The effects of 4 and 8 weeks fasting at 16 °C were studied in rainbow trout, Salmo gairdneri Richardson. After 4 and 8 weeks, the wet weights of the intestine of fasted animals are respectively 64% and 69% lower than those of fed animals. These effects especially concern the mucosal tissue. Glycine absorption (0·5 and 10 mm) was studied using an in vivo perfusion technique. After 4 weeks, the absolute amounts of 0·5 mm glycine absorbed by fasted and fed fish are similar. With 10 mm glycine, the absorption is slightly lower in fasted trout (–19%). After 8 weeks these differences are more marked, with glycine concentrations of 10 mm (– 42%). Results expressed per 100 g body weight showed that these differences result partly from a weight gain of fed trout. Absorption expressed in terms of weight of dry intestine is higher in 4 and 8 weeks fasted animals, principally for the lower amino acid concentration (+61% and +111%). Larger differences were apparent when the absorptions were expressed in terms of dry weight of mucosal tissue (+122% and +225%).

Absorption of free and peptide-linked glycine and phenylalanine in children with active celiac disease.

Using a marker perfusing technique, the jejunal absorption rates of glycine and phenylalanine from test solutions containing either the free amino acids or glycyl-phenylalanine (30 mM each) were studied in five children with active celiac disease and in three controls. Changes in plasma amino acid levels during intestinal loading were also investigated. Mean values of intestinal uptake rates (micromoles/min/20 cm segment) in patients and controls were found to be as follows: free glycine, 19.3 +/- 21.8 and 74.5 +/- 10.3; peptide-linked glycine, 45.0 +/- 12.4 and 110.7 +/- 20,1; free phenylalanine, 33.6 +/- 19.6 and 106.1 +/- 10.6; peptide-linked phenylalanine, 44.5 +/- 14.3 and 113.6 +/- 11.1, respectively. Thus, amino acid absorption is higher from peptide-linked glycine and phenylalanine, and the advantage of individual amino acid absorption from dipeptide seems to be maintained in the disease state. Changes of amino acid levels in plasma do not reflect impaired intestinal absorption because the levels of phenylalanine increased to the same extent in patients and in controls, and the increment of glycine was found to be higher in the patients group.

Rates of in vivo intestinal absorption of glycine and glycylglycine by rainbow trout ( Salmo Gairdneri R.)

1. 1. The in vivo absorption rate of glycylglycine by rainbow trout was compared to that of glycine from solutions containing the same number of glycine units per unit volume, using a perfusion method. 2. 2. Glycylglycine hydrolase activity was also assayed on analogous but not perfused intestinal segments and on purified brush border membranes. 3. 3. Net absorption of glycine from respectively, 10 and 100 mM glycylglycine, is comparable to the absorption from 20 and 200 mM glycine. 4. 4. Glycine can be detected in the final perfusate after perfusions with dipeptide, especially with 100 mM glycylglycine. 5. 5. This glycine appears to represent an efflux of amino acid derived from glycylglycine previously absorbed by the intestine. 6. 6. Glycylglycine is hydrolysed to some extent by brush border membranes but more importantly by cytoplasmic enzymes. 7. 7. By taking into account the efflux glycine, it can be calculated that, as in mammals, glycine uptake by rainbow trout is more rapid from glycylglycine than from the equivalent free amino acid, especially for the highest concentration tested.

Effect of a single oral dose of malathion on D-glucose and glycine uptake and on brush border enzymes in rat intestine

The effect of a single oral dose of malathion (1 g/kg body wt.) on the digestive and absorptive functions of the intestinal epithelium has been investigated in rats. The absorption of glucose and glycine was considerably reduced (35%) in pesticide fed animals compared to controls. The activities of brush border sucrase, lactase, alkaline phosphatase, Mg 2+-ATPase and lactate dehydrogenase were also significantly depressed in malathion exposed rats, but there was no change in the leucine aminopeptidase levels under these conditions. Mucosal DNA, RNA and protein contents remained unaltered in pesticide toxicity. These results suggest that malathion toxicity induces functional derangements of the intestine.

Absorption of glycine and proline from the small intestine of rats infected with Eimeria nieschulzi.

The absorption of glycine and proline through the jejunum and ileum of rats with an Eimeria nieschulzi infection was impaired when the amino acids were presented to the mucosal surface as either a mixture or the dipeptide, glycyl-proline.

Absorption of glycine, L-alanine and L-phenylalanine in the midgut of the larvae ofBombyx mori

A net absorption of glycine, L-alanine and L-phenylalanine occurs across the isolated midgut of the larvae ofBombyx mori. Although glycine and L-phenylalanine are not metabolized, L-alanine is converted by the midgut and has a metabolic effect on the transepithelial electrical potential difference of the tissue.

Effect of environmental oxygen tensions on in vivo intestinal absorption of glycine by the rainbow trout (Salmo gairdneri r.)

1.1. Glycine absorption was studied in vivo, at 14°C, on rainbow trout after a rapid decrease of oxygen levels of water (8–9 ppm to 2–3 ppm). Intestines were perfused on swimming trout, using different saline solutions and two glycine concentrations: 0.5 mM and 10 mM.2.2. When the perfusate contains 150 mEq Na, hypoxia produces two opposite responses according to the glycine concentration: an increased uptake for 0.5 mM glycine and a decrease for 10 mM amino acid.3.3. This last response is replaced by an increased uptake when sodium is replaced by potassium.4.4. These effects of hypoxia are restricted when sodium and potassium are replaced by mannitol.

A study of intestinal absorption in vivo and in vitro of different concentrations of glycine by the rainbow trout ( Salmo gairdnerii richardson)

1. 1. Intestinal absorption of different concentrations of glycine has been studied in vivo and in vitro in the rainbow trout in the entire intestine or in fragments. 2. 2. Glycine absorption in vitro is a saturable phenomenon which obeys Michaelis-Menten kinetics in the range of 0.5–10 mM. The transport constant ( K t ), maximal transport rates (VTM) and net liquid fluxes are all higher in the middle portion of the intestine (midgut) than in the posterior portion (hindgut). 3. 3. Glycine absorption by the hindgut in vivo is a saturable phenomenon in the concentration range of 0.5–10 mM. Absorption by the midgut, however, is a linear function of the initial glycine concentration. Net liquid movements are only slight in both portions of the intestine.

A study of energized transport mechanisms of glycine absorption by the rainbow trout ( Salmo gairdneri richardson)

1. 1. The effects of metabolic inhibitors on in vitro glycine absorption and net water fluxes were studied. Previous controls of oxygen uptake by poisoned intestines were performed. 2. 2. A slight inhibition of glycine absorption was induced by NaF (5 × 10 −3 M) or 2:4 DNP (10 −5 M) in midgut or hindgut, especially when the saline was devoid of Ca 2+ and Mg 2+ (NaF). NaF caused a reversion of net water fluxes. 3. 3. Anoxia resulted in an important inhibition of glycine absorption and in a complete reversion of net water fluxes. 4. 4. The effects of 2:4 DNP and anoxia were minimized when the saline was devoid of Na +. Furthermore, ouabain strongly depressed glycine absorption. 5. 5. These experiments indicate that in trout, as in mammals, glycine transport is achieved by active processes coupled with Na +-K + gradients.

Heavy metal action on transintegumentary absorption of glycine in two annelid species

Absorption of 14C-glycine from ambient sea water across the body surface of the oligochaete Enchytraeus albidus Henle was, after 6 h preincubation, significantly reduced in the presence of 0.1 to 0.15 ppm mercury, 0.25 ppm copper, 1.5 ppm silver, and 2 ppm cadmium. Addition of heavy metal salts reduced maximum uptake rates (Vmax), without affecting transport constants (Kt). Influx of 14C-glycine remained unchanged in the presence of up to 10 ppm aluminium, chromium, iron, lead, molybdenum, vanadium, and zinc. Effects of up to 150 ppm nickel, manganese, cobalt and selenium were negligible. Inhibition of glycine absorption by mercury and cadmium in the polychaete Nereis diversicolor Muller is almost identical with results presented for E. albidus. Transintegumentary solute absorption in soft-bodied marine invertebrates obviously represents a suitable biological function for studies on heavy metal toxicity. The close relationship between rates of heavy metal absorption, inhibition of transintegumentary glycine uptake, and acute toxicity is discussed.

Effect of systemic bacterial infection on absorption rates of l-histidine and glycylglycine from the human jejunum in vivo

Jejunal absorption rates of L-histidine (from a 100 mmole/liter solution) and glycylglycine (from a 50 mmole/liter solution) were determined with a souble-lumen tube perfusion system in vivo in 12 Zambian African men; six had acute bacterial pneumonia (infection group) and six had no clinical evidence of a bacterial infection (control group). With this experimental design the mean rate of histidine absorption was significantly higher in the infection compared with the control group, but mean rates for glycine absorption from glycylglycine were not significantly different. During the glycylglycine infusions, the luminal disappearance rate of the intact peptide was significantly greater than the total glycine absorption rate. The correlation between individual histidine and glycylglycine absorption rates was significant. That is probably because after intracellular hydrolysis and efflux to the lumen, some glycylglycine is reabsorbed as free glycine by the amino-acid transfer mechanism, and the rate of that has previously been shown to be increased in subjects with systemic bacterial infections.