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At least 109 records · Page 6Linked to original sources
PubMed1992

Improvement of large intestinal absorption of insulin by chemical modification with palmitic acid in rats.

The intestinal absorption of 125I-labelled palmitoyl insulin was examined following administration into in-situ closed large intestinal loops of rats. When mono- and dipalmitoyl insulins (Palins-1 and Palins-2, respectively) were administered in polyoxyethylene hydrogenated castor oil (HCO 60) micellar system into intestinal loops, a marked increase in plasma radioactivity and a corresponding disappearance of residual radioactivity in the intestinal lumen were observed in the following rank order: Palins-2 greater than Palins-1 greater than native insulin. In addition, the derivatives were more stable than native insulin in the mucosal tissue homogenates of the large intestine. These results suggest that chemical modification of insulin with palmitic acid may not only increase the lipophilicity of insulin but also reduce its degradation, resulting in the increased transfer of insulin across the large intestinal mucous membrane. The linoleic acid-HCO 60 mixed micelles system did not have a significant effect on the large intestinal absorption of radioactivity associated with the lipophilic insulin analogues.

Animals↗
PubMed1978

Effect of low calcium and low phosphorus diets on the intestinal absorption of phosphate in intact and parathyroidectomized pigs.

The intestinal absorption of phosphate has been studied in conscious pigs, each prepared with a Thiry-Vella loop of jejunum. The feeding of diets low in either calcium or phosphorus caused a significant increase in the efficiency of absorption of phosphate from the solution used to perfuse the jejunal loop in both intact and parathyroidectomized (PTX) pigs. An intravenous infusion of parathyroid hormone (0.22 u. kg-1 h-1) into a PTX pig also enhanced the absorption of phosphate. The increase in the absorption of phosphate when the low phosphorus diet was fed was not caused by an increase in the concentration gradient of phosphate ions between the jejunal lumen and blood. It is concluded that the intestinal absorption of phosphate shows similar changes to those of calcium when diets low in calcium or phosphorus are fed and that parathyroid hormone, although capable of stimulating the absorption of phosphate, is not essential for this adaptation. These effects are probably brought about by changes in the renal production and mucosal uptake of 1,25-dihydroxycholecalciferol, the active metabolite of vitamin D3.

Animals↗
PubMed1970

Intestinal absorption of calcium-47 after treatment with oral oestrogen-gestogens in senile osteoporosis.

Intestinal absorption of radiocalcium was measured in 15 postmenopausal women with osteoporosis before and after six months' treatment with an oral oestrogen-gestogen combination. Comparison with a control group indicated a significant improvement in intestinal absorption after treatment. Though there is no evidence that oestrogens have an anabolic effect on human bone, these results indicate that they affect the intestinal absorption of calcium directly.

Aged↗
PubMed1989

Non-linear intestinal absorption kinetics of cefadroxil in the rat.

Absorption of cefadroxil in a selective intestinal absorption area (the proximal third of the small intestine) of the anaesthetized rat, at seven initial perfusion concentrations, ranging from 0.01 to 10.0 mg mL-1, is shown to be a non-linear transport mechanism. With the aid of computer-fitting procedures based on differential and integrated forms of Michaelis-Menten equation, Vm and Km values of 36.7-37.3 mg h-1 and 12.0-13.0 mg, respectively, were found. The statistical parameters were better than those obtained both for first-order and for combined Michaelis-Menten and first-order kinetics. There is no evidence for substantial passive diffusion processes. The results reported here, together with allometric considerations and literature data analysis, may help to explain some particular non-linear features of plasma level curves associated with the administration of fairly high oral doses of cefadroxil to humans.

Animals↗
PubMed1985

Intestinal absorption of arsenate in the chick.

The intestinal absorption of arsenate(As(V)) has been investigated in the chick by means of the in situ ligated duodenal loop technique. By this procedure, it was observed that arsenate is rapidly and essentially completely absorbed (80-95%) from the lumen at As(V) concentrations up to 5 mM, declining to about 50% absorption at 50 mM. Transfer from the intestinal lumen to the mucosal cells at low As(V) concentration (0.1 mM) is rapid, while transfer from the mucosal cells to the body occurs more slowly. At stable As(V) concentrations greater than 1 mM, fractional mucosal cell accumulation of As(V) remains constant, while fractional transfer to the body declines. However, total mucosal accumulation of As(V) and that transferred to the body increase in a linear logarithmic fashion from 0.05 to 5 mm As(V). The results indicate that As(V) readily penetrates both the mucosal and serosal surfaces of the epithelial membrane. Furthermore, arsenate and phosphate do not appear to share a common transport pathway in the duodenum and no evidence was obtained for any interaction between the two at this level. Vitamin D3 administration to rachitic chicks was effective in significantly elevating duodenal arsenate absorption, acting primarily to enhance serosal transport.

Administration, Oral↗
PubMed1986

[Intestinal absorption of calcium gluconate and oseine-mineral complex: an evaluation by conventional analyses].

Calcium (Ca) preparations are widely used in the treatment of osteoporosis, usually as soluble salts. Tolerance might be improved by prescription of slowly dissolved Ca preparations, since Ca is also absorbed distally, even in the colon. In this regard the use of natural forms of Ca might be advantageous, but natural products cannot be labeled reliably for easy evaluation of their absorption. To study the intestinal absorption of an osseino-mineral complex (Ossopan) in comparison with Ca-gluconate, healthy males were investigated by means of conventional blood and urinary measurements before and after ingestion of either substance containing 1.58 g Ca. All subjects were placed on a standard diet 2 days before and during test day. Ca-gluconate (n = 7) evoked a marked and transient rise in plasma ionized calcium; total plasma calcium and urinary calcium followed a parallel course, while plasma and urinary phosphate decreased. After administration of osseino-mineral complex (n = 6), a slow but sustained elevation of plasma ionized calcium was observed while total calcium remained unchanged when corrected by the plasma proteins. Plasma phosphate and proteins increased, as did urinary phosphate. Comparing the 24-hour urine of the test day with that of the previous day, the rise in calcium excretion was slightly greater in the subjects treated by osseino-mineral complex than in those who were given Ca-gluconate, while phosphate excretion increased in the first group and decreased in the second. It is concluded that the bioavailability of Ca in osseino-mineral complex is as good as, if not better than, that of Ca-gluconate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Improvement of intestinal absorption of thyrotropin-releasing hormone by chemical modification with lauric acid.

Intestinal absorption of 125I-labelled lauryl thyrotropin-releasing hormone (Lau-TRH), a novel lipophilic derivative of TRH, was examined by rat in-situ closed intestinal loops. At a dose of 1 mumol per rat into the small intestine, a significant increase in percent of dose in plasma radioactivity of Lau-TRH was observed in comparison with that of TRH. A dose-dependent decrease in percent of dose in plasma radioactivity of TRH was noted, suggesting a saturable process of TRH transport. In contrast, the percent of dose in plasma radioactivity of Lau-TRH increased with increasing dose of Lau-TRH. The stability of TRH and Lau-TRH was studied in plasma and rat small intestinal homogenates. Lau-TRH was more stable than TRH in rat plasma. These results suggest that chemical modification of TRH with lauric acid may not only increase the lipophilicity of TRH but also reduce the degradation of TRH, resulting in the increased plasma radioactivity of TRH. On the other hand, Lau-TRH was gradually converted to TRH in the intestinal mucosal homogenate. These findings indicate that chemical modification of TRH with lauric acid might be a useful approach for improving the intestinal absorption of this peptide.

Animals↗
PubMed1989

Relationship between in vivo first-order intestinal absorption rate constant and the membrane permeability clearance.

An attempt was made to explore the quantitative relationship between the intestinal absorption data obtained from in vivo studies and in situ perfusion studies. The time course of the fraction remaining to be absorbed of L-glucose, erythritol, and urea in the small intestine following the intrajejunal administration to rats was described by a one-compartment model. Thus derived first-order intestinal absorption rate constants (ka) obtained from the in vivo studies in rats were compared with the membrane permeability clearances (CLa,m) estimated in a single-pass perfusion system. Not only were ka and CLa,m in the same increasing order of L-glucose less than erythritol less than urea, but also the operational luminal volumes given as CLa,m/ka were in agreement with the in vivo luminal volume of jejunum estimated by an inulin dilution method. This result suggests that the in vivo intestinal absorption rate (or ka) can be correlated with the intestinal membrane permeability (or CLa,m) by taking the in vivo luminal volume into account.

Animals↗
PubMed1985

Impaired intestinal absorption of riboflavin in experimental uremia.

Increased plasma and red blood cell concentrations of riboflavin have been reported in uremia. The possible role of altered intestinal absorption of riboflavin in the genesis of this abnormality is not known. For this reason we examined the intestinal absorption of riboflavin in rats made uremic by subtotal nephrectomy and sham-operated (control) rats in vivo using the recycling perfusion technique and in vitro using the everted-sac technique. Paradoxically, the results showed a significant impairment of intestinal absorption of riboflavin in vivo in uremic rats compared to the control group. However, no significant difference was observed in riboflavin transport in vitro. We conclude that the intestinal absorption of riboflavin is decreased in experimental uremia and cannot account for the reported increase in its plasma and red blood cell concentrations.

Animals↗
PubMed1986

Intestinal absorption of aluminum in rats: effect of intraluminal pH and aluminum concentration.

The intestinal absorption of aluminum (Al) was studied in an in situ perfusion system of rat small intestine in combination with systemic and portal blood sampling. The jejunum-ileum was perfused with media containing 4.63, 9.25 and 18.50 mmol l-1 Al chloride at pH 4.0 and 7.0. Both mucosal retention was not affected by pH but at lower pH more Al was released into the blood. The amount of Al which appeared in the blood was linearly related to the mucosal retention. The Al release into the blood was much less (mumol l-1) than the mucosal retention (mmol l-1). It is concluded that the intestinal absorption of Al is pH- and concentration-dependent.

Aluminum↗
PubMed1984

Avian species differences in the intestinal absorption of xenobiotics (PCB, dieldrin, Hg2+).

Intestinal absorption of a polychlorinated biphenyl, dieldrin, and mercury (from HgCl2) was measured in adult Northern bobwhites, Eastern screech owls, American kestrels, black-crowned night-herons and mallards in vivo by an in situ luminal perfusion technique. bobwhites, screech owls and kestrels absorbed much more of each xenobiotic than black-crowned night-herons and mallards. Mallards absorbed less dieldrin and mercury than black-crowned night-herons. Mercury absorption by kestrels was more than twice that in screech owls and eight times that observed in mallards. Pronounced differences in xenobiotic absorption rates between bobwhites, screech owls and kestrels on the one hand, and black-crowned night-herons and mallards on the other, raise the possibility that absorptive ability may be associated with the phylogenetic classification of birds.

Animals↗
PubMed1990

Epithelial transport of drugs in cell culture. I: A model for studying the passive diffusion of drugs over intestinal absorptive (Caco-2) cells.

A human intestinal cell line, Caco-2, was used as a model to study the passive diffusion of drugs across intestinal epithelium. The cells formed continuous monolayers when grown on permeable filters of polycarbonate. After 10 days in culture, the monolayers had a transmembrane resistance of approximately 260 ohms.cm2 and a cell density of 0.9 x 10(6) cells/cm2. At this time the cells were impermeable to [14C]polyethyleneglycol (MW 4000). These characteristics remained constant for 20 days (i.e., from day 10 to day 30). Six beta-blocking agents with a 2000-fold range of lipophilicity were studied for their transepithelial transport properties. The transport parameters were independent of drug concentration and transport direction. The apparent permeability coefficients ranged from 41.91 +/- 4.31 x 10(-6) cm/s for the most lipophilic drug, propranolol, to 0.203 +/- 0.004 x 10(-6) cm/s for the most hydrophilic drug, atenolol. The transport parameters were compared with those published for rat ileum. The transport rates were similar for four out of five drugs. Atenolol was transported at a slower rate in the Caco-2 model, which may be explained by the fact that the Caco-2 cells form a tighter epithelium than the rat ileal enterocytes. The findings of this paper indicate that Caco-2 cells may be used to model the intestinal absorption of drugs.

Adrenergic beta-Antagonists↗
PubMed1985

Intestinal absorption and excretion of zinc in streptozotocin-diabetic rats as affected by dietary zinc and protein.

65Zn was used to examine the effects of dietary zinc and protein on true zinc absorption and intestinal excretion of endogenous zinc by an isotope dilution technique in streptozotocin-diabetic and control rats. Four groups each of diabetic and control rats were fed diets containing 20 ppm Zn, 20% egg white protein (HMHP); 20 ppm Zn, 10% egg white protein (HMLP); 10 ppm Zn, 20% egg white protein (LMHP); and 10 ppm Zn, 10% egg white protein (LMLP). Measurement of zinc balance was begun 9 d after an i.m. injection of 65Zn. True zinc absorption and the contribution of endogenous zinc to fecal zinc excretion were calculated from the isotopically labeled and unlabeled zinc in the feces, duodenum and kidney. Results from the isotope dilution study indicated that diabetic rats, but not control rats, absorbed more zinc from 20 ppm zinc diets than from 10ppm zinc diets and that all rats absorbed more zinc from 20% protein diets than from 10% protein diets. Furthermore, all rats excreted more endogenous zinc from their intestines when dietary zinc and protein levels resulted in greater zinc absorption. In diabetic and control rats, consuming equivalent amounts of zinc, the amount of zinc absorbed was not significantly different, but the amount of zinc excreted by the intestine was less in the diabetic rats. Decreased intestinal excretion of endogenous zinc may be a homeostatic response to the increased urinary excretion of endogenous zinc in the diabetic rats and may also lead to the elevated zinc concentrations observed in some organs of the diabetic rats.

Analysis of Variance↗
PubMed1981

Biopharmaceutical studies on hydantoin derivatives. I. Physico-chemical properties of hydantoin derivatives and their intestinal absorption.

The physico-chemical properties of a series of hydantoin derivatives and their intestinal absorption from solution were studied. The introduction of the benzenesulfonyl group at the 1-position of the hydantoin ring greatly affects the physico-chemical properties: the acid dissociation constants were increased 1000-fold and the partition coefficients were increased 100- to 1000-fold in the chloroform/water system and 10- to 100-fold in the n-octanol/water system. The solubilities of 1-benzenesulfonylhydantoin derivatives increased with increasing pH of the solution at pH more than 5, but the solubilities of the 1- unsubstituted hydantoin derivatives were scarcely dependent on the pH of the solution in the pH 1 to 8 region. The intestinal absorption from solution was found to be caused by the passive transport according to the first-order kinetics. The rate constants of absorption of 1-benzenesulfonylhydantoin derivatives were rather large even under the condition where they were 99% ionized in the solution than that of the corresponding 1-unsubstituted hydantoin derivatives which exist mainly as the unionized from under the same condition. The intestinal absorption from a solution and the partitioning to chloroform produced linear free energy relationships to each other for the 1-benzenesulfonylhydatoin derivatives and for the 1-unsubstituted hydantoin derivatives independently. However when the partition coefficients in the n-octanol/water system were applied, the hydroxyl derivatives were found to deviate from linear relationships. On the basis of the results, a suggestion was made on the in vivo behavior and the bioavailability.

Animals↗
PubMed1987

Effect of total colectomy and mucosal proctectomy on intestinal absorptive capacity in dogs.

Changes in intestinal absorptive capacity for water and electrolytes were investigated in dogs after total colectomy and mucosal proctectomy reconstructed with interposing jejunum into the anorectal area. Rate of absorption of water and sodium from the ileum increased significantly at 29 weeks postoperatively. The absorption of water, sodium, and chloride in the jejunum was significantly higher than in the neorectum. The net secretion rate of potassium increased significantly in the ileum and neorectum. The authors suggest that intestinal adaptation achieved after proctocolectomy is enhanced in the jejunum and ileum rather than in the neorectum.

Animals↗
PubMed1977

Intestinal absorption of alpha-tocopherol in the unanesthetized rat. The influence of luminal constituents on the absorptive process.

3H-alpha-tocopherol intestinal absorption was studied in the unanesthetized rat. The rate of alpha-tocopherol absorption remained linear over a wide range of concentrations (4 nM to 400 micrometer). Increasing the sodium taurocholate concentration in the micellar infusate up to 15 mM did not increase the rate of absorption of the vitamin. Addition of long-chain fatty acids to the micellar infusate decreased the absorption rate of the vitamin (p less than 0.05). The decrease was most significant (p less than 0.01) following the addition of the polyunsaturated linolenic (C18:3) acid. Increasing the hydrogen ion concentration in the perfusate increased the absorption rate of alpha-tocopherol. The present experiments in vivo support the conclusions drawn from in vitro uptake experiments which indicated that alpha-tocopherol is absorbed by a passive diffusion process. These experiments indicate that micellar expansion with polyunsaturated fatty acids interferes with the absorption of alpha-tocopherol and may result in deficiency of the vitamin.

Animals↗
PubMed1988

[Postoperative small intestine absorption--principles for enteral nutrition].

The intestinal absorption of nutrients is disturbed to an extent dependent on the degree of trauma in the immediate postoperative period. In a clinical study, the d-xylose absorption was investigated in 3 groups of patients after cholecystectomy. On the day of surgery a significant restriction of the absorption could be observed after intraduodenal administration. After gastric and duodenal administration of d-xylose and simultaneous enteral early nutrition a significant restriction of absorption could be observed on the day surgery was carried out. Optimal conditions for early nutrition can be achieved by combining intraduodenal feeding and a continuous decompression of the stomach. In cases of a gastric drainage an improvement of the postoperative absorptive function can be supported by the results of the nitrogen balance. In 4 pigs (type: country race) the step-by-step normalization of the absorptive kinetics could be demonstrated after catheters were implanted into the portal and subclavian veins.

Adult↗