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A number of factors influence gastrointestinal tissue structure and mechanical properties such as the physical environment and diseases like partial obstruction. Hence multi-axial biomechanical properties are important for understanding the pathophysiology of the obstructed intestine. The aim was to estimate the multi-axial biomechanical properties, in particular with focus on the shear modulus. Partial obstruction of mid-jejunum was created surgically by placement of a polyethylene ring for two weeks in seven male rats. Sham operation was made in five other rats. At the time for termination, three 6-cm intestinal segments were used for histological and mechanical analysis. The segments were obtained distal (S1), proximal (S2) and further proximal (S3) to the site of obstruction or suturing site. The tri-axial testing included simultaneous torsion, inflation and longitudinal stretching. The lumen size, wall thickness, wall cross-sectional area, and muscle layer thickness increased in S2 and S3 of the obstructed rats (p < 0.001) with the most pronounced changes in S2. The opening angle decreased in S2 in the obstructed group (p < 0.05). The tissue stiffness increased in circumferential and longitudinal direction where as it was softer in shear direction, especially in S2 (p < 0.01). In conclusion, the histomorphological and mechanical properties including shear properties remodeled proximal to the intestinal obstruction site.

In this article we study the effect of diets supplemented with two strains of Lactobacillus delbruckii subsp. bulgaricus (B3 and A13, which produced the highest and lowest amount of exopolysaccharide, respectively) on generation of intestinal nitric oxide (NO) and antioxidant status. The oxidative status in terms of thiobarbituric acid-reactive substances (TBARS) and NO levels in small intestinal tissues were measured. We also determined intestinal nonenzymatic antioxidant levels after supplementation with two strains of L. delbruckii subsp. bulgaricus. In rats, dietary supplementation with both lactobacilli strains resulted in a nearly 1.5-fold increase in NO level in the small intestine. Increases in NO production may contribute to lipid peroxidation in the small intestine. However, at the same time, diets supplemented with both strains of L. delbruckii subsp. bulgaricus enhance the antioxidant capacity of the gastrointestinal system in rats. These probiotics could be used as important adjuvants to maintain balance in the gut, although more studies are required to demonstrate their efficacy in humans.

The purpose of this study was to investigate liver and intestinal ABCA1 expression and plasma HDL-C level in response to treadmill-running training in rats. Twenty adult Wistar male rats (17–18 weeks old, 300–322 g) were divided into control (n = 10) and Training (n = 10) groups. Training group trained at 25 m/min (0% grade) for 60 min/day, 5 days/week for 12 weeks. Rats were killed 48 h after the last session of training. The intestinal and liver ABCA1 mRNA expression was found to be significantly higher in trained compared to control group (P

Nitroglycerin (NTG) has been reported to possess preconditioning-like (PCL) protections on heart and other tissues. Our previous studies showed that NTG has acute PCL effects on rat small intestine. The present studies were designed to study whether NTG has delayed PCL protection on rat small intestine and to explore its mechanism(s).The intestine lesions were evaluated by histologic examination and serum lactate dehydrogenase (LDH) measurement. The effects of nitric oxide (NO), cGMP, and alpha-calcitonin gene-related peptide (CGRP) synthesis on the effects of NTG were analyzed.Pretreatment with NTG (0.12 mg/kg i.v.) 24 h before ischemia-reperfusion (I/R) of super mesenteric artery significantly reduced histologic lesions and serum LDH with elevated blood levels of NO and CGRP. Inhibition of guanylate cyclase by methylene blue (30 mg/kg i.p.) or specific depletion of transmitters in capsaicin-sensitive sensory nerve by capsaicin (50 mg/kg s.c.) abrogated the protection conferred by NTG. Reverse-transcription polymerase chain reaction analysis showed that NTG upregulates the expression of alpha-CGRP messenger RNA (mRNA), but not beta-CGRP mRNA in lumbar dorsal root ganglia.In conclusion, NTG prevents rat small intestine from I/R injury by delayed PCL effects 24 h after administration. The protective effects are mediated by NO-cGMP pathway and alpha-CGRP upregulation.

Purpose. The aim of this study is to investigate the effects of 50% ethyl acetate extracts of grapefruit juice (GFJ) and orange juice (OJ) on the transport activity of P-glycoprotein (P-gp) in the rat small intestine.

Tension–strain relations and morphometric data were studied in isolated segments of the jejunum and distal ileum in untreated diabetic rats, insulin-treated diabetic rats, and nondiabetic control rats. Diabetes was induced by a single intravenous injection of streptozotocin (28 mg/kg body wt). All injected rats developed hyperglycemia. The experiment was terminated after 28 days and the intestinal segments were superfused with saline solution containing papaverine to abolish contractile activity. Stepwise inflation of a balloon in which the cross-sectional area (CSA) was measured provided the luminal pressure-loading stimulus. The circumferential tension–strain relation was derived from steady-state values of internal radius and applied pressure. The intestinal weight, length, and weight per unit length increased significantly in untreated diabetic rats compared to the two other groups (P 0.2). The tension–strain relations in jejunum and distal ileum were nonlinear and the curves for the two diabetic groups were shifted to the left compared to the curve for controls (P < 0.05), indicating increased wall stiffness. The histomorphometric data showed increased wall thickness in untreated diabetic rats compared to the two other groups both in jejunum and distal ileum (P < 0.02). Mucosal, submucosal, and muscle layer thicknesses did not differ between the three groups. No significant association was found between the histomorphometric and biomechanical parameters.

Rectal administration of indomethacin induces longitudinal ulcers in the rat small intestine. The current study investigated a sequence of progressive villus injury in this enteropathy, especially by the use of scanning electron microscopy. The initial change was the distortion of several villi on the mesenteric side in the mid-small intestine identified at 0.5 h, even though there was no obvious change under light microscope or dissecting microscope at this time. During the subsequent 2h, distortion of the villi was accompanied by several epithelial defects, and epithelial detachment occurred on the villi tips. Extension of epithelial defects and exposure of the villus core progressed during subsequent periods. The injured villi were confluent with each other on the mesenteric side throughout the 12h after dosing. These findings suggest that the initial mucosal injury induced by the rectal route of administration was not extensive; rather, several villi were focally damaged on the mesenteric side in the mid-small intestine, eventually resulting in a longitudinal ulcer. Although the overall progression after indomethacin administration by the rectal route was similar to that occurrmg after subcutaneous administration, villus change seems to occur much earlier after rectal dosage.

The tachykinin NK2 receptors present in membranes of rat small intestine were characterized by means of tachykinin receptor agonists and antagonists, by using the natural agonist, NKA, or the nonpeptide antagonist SR 48968, as radioligands. The affinity of the antagonists was independent of the radioligand used, whereas the NK2 receptor selective agonists showed a different binding profile according to the radioligand. In particular, when using [125I]NKA, NKA and NKA(4-10) bound to a high affinity site, whilst [beta-Ala8]NKA(4-10) and GR 64349 bound to a high and a low affinity site; the high affinity site was still detected in the presence of 100 microM GppNHp which produced a strong inhibition of the specific binding of [125I]NKA. On the other hand, when using [3H]SR 48968, NKA bound to a high affinity site, [beta-Ala8]NKA(4-10) bound to a low affinity site and NKA(4-10) and GR 64349 bound to a high and a low affinity site; in this case, the high affinity site was no longer detected in the presence of 1 microM GppNHp, which did not reduce the specific binding of [3H]SR 48968 to NK2 receptors. We interpreted these data as an indication that in the rat small intestine membranes [125I]NKA labels multiple conformations of G protein-coupled NK2 receptor which are distinguished by the use of selective receptor agonists, but not by peptide or nonpeptide antagonists.

Microbial modulation of myoelectric activity in small intestine was studied. Germ-free male Sprague-Dawley rats were equipped with bipolar electrodes from the duodenojejunal junction to the midpoint of small intestine. Prior to and one week after introduction of conventional intestinal microflora, 32 +/- 5% and 61 +/- 5% (mean +/- SE), respectively, of activity fronts of the migrating myoelectric complex reached the midpoint (P0.05), and the interval between activity fronts in proximal jejunum was reduced from 31.2 +/- 2.0 min to 17.5 +/- 0.8 min, respectively (P0.01). The pattern of propagation was more regular after conventionalization. Slow-wave frequency in proximal jejunum was 38.5 +/- 1.2/min in germ-free rats and 43.0 +/- 0.8/min in conventional rats (P0.01), but introduction of microflora failed to increase the frequency in germ-free rats. The frequency of spike potentials succeeding jejunal infusion of 5 ml of 12.5% glucose remained unchanged after conventionalization. Statistical analyses showed that the interval between activity fronts varied mainly within rats, whereas the propagation velocity showed statistically significant variability between rats (P0.01), regardless of intestinal microflora. Luminal control by the resident microflora is important for physiological cycling and aboral propagation of the migrating myoelectric complex, but seems to be of no major consequence for postprandial myoelectric response.

The transport of taurine across adult Sprague-Dawley rat small intestine was studied in vitro using small intestinal strips. The kinetics of the transport mechanism were investigated under both steady-state and influx conditions. Our findings were compatible with the presence of two distinct transport mechanisms; a linear non-carrier mediated component and a saturable carrier mediated component, with almost equal contribution from each. The mediated component was found to be largely Na(+)-dependent and exhibited marked inhibition by B-alanine and structurally related sulfur amino acids.

Blood loss-induced ischemia reduced intestinal electrical spike activity and delayed or blocked the migrating myoelectric complex. A single session of mesodiencephalic modulation significantly intensified electrical discharges, stimulated contractions of the small intestine, and restored normal cycles of the migrating myoelectric complex.

The uptake of selenite, selenate and selenomethionine (SeMet) was performed with brush border membrane vesicles (BBMV) prepared from rats fed selenium-deficient and supplemented diets. At equilibrium (60 min), the uptake of 75Se from [75Se]selenite ranged from 16.5 to 18.9 nmol mg-1 protein. There was a curvilinear relationship in the uptake of selenite over a concentration range of 10-1000 microM. About 2 nmol mg-1 protein was obtained with selenomethionine (SeMet) which occurred between 90 and 180 s. In contrast to selenite, there was a linear relationship in the initial uptake of SeMet over a concentration range of 10-1000 microM. The uptake of selenate was approximately 50-fold lower than selenite, reaching 350 pmol mg-1 protein. Dietary selenium level had no effect on the rate of 75Se accumulation by BBMV. Dramatic differences are found in the uptake and binding of selenium by BBMV incubated with different selenocompounds.

The apparent extracellular space (ECS) of rat jejunum, everted and cannulated "in vitro", has been measured by using extracellular markers of different molecular weights. The markers used were two polyethyleneglycols, 14C and 3H labelled (14C-PEG MW 4000 and 3H-PEG MW 900) and 3H-sucrose. The ECSs for the mucosal and serosal sides have been separately determined throughout the time course, and it has been found that the two spaces are identical when PEG 4000 was used but the serosal ECS is almost the double when using PEG 900. The serosal ECS determined with sucrose is four times as big as the mucosal ECS. It seems reasonable to conclude that the best marker for the measure of total apparent ECS is sucrose, placed in the serosal compartment, taking into account that the mucosal ECS is four times smaller than the serosal one. All the markers used reach equilibrium with ECS, more rapidly in the mucosal than in the serosal ECS. Finally, by comparing cell water and cell Na concentrations, one observes that there is a statistical difference between the results obtained by using PEG 4000 as an extracellular marker and those obtained with sucrose.

Two major cell types, goblet and absorptive cells, dominate the epithelial lining of small intestinal villi. We used freeze-fracture replicas of rat ileal mucosa to examine the possibility that tight junction structure, known to relate to transepithelial resistance, might vary with cell type. Tight junctions between absorptive cells were uniform in structure while those associated with villus goblet cells displayed structural variability. In 23% of villus goblet cell tight junctions the strand count was less than 4 and in 30% the depth was less than 200 nm. In contrast, only 4% of absorptive cell tight junctions had less than 4 strands and only 9% had depth measurements less than 200 nm. Other structural features commonly associated with villus goblet cell tight junctions but less commonly with absorptive cell tight junctions were: deficient strand cross-linking, free-ending abluminal strands, and highly fragmented strands. Both in vivo ileal segments and everted loops were exposed to ionic lanthanum. Dense lanthanum precipitates in tight junctions and paracellular spaces were restricted to a subpopulation of villus goblet cells and were not found between villus absorptive cells. After exposure of prefixed ileal loops to lanthanum for 1 hour, faint precipitates of lanthanum were found in 14% of tight junctions and paracellular spaces between absorptive cells compared to 42% of tight junctions and paracellular spaces adjacent to villus goblet cells. When tested in Ussing chambers, the methods used for lanthanum exposure did not lower transepithelial resistance. Everted loops exposed to ionic barium and examined by light microscopy showed dense barium precipitates in the junctional zone and region of the paracellular space of villus goblet cells but not in these regions between absorptive cells. However, the macromolecular tracers, microperoxidase, cytochrome c and horseradish peroxidase, were excluded from both villus goblet cell and absorptive cell paracellular spaces in in vivo segments. These findings suggest that a subpopulation of villus goblet cells may serve as focal sites of high ionic permeability and contribute to the relatively low resistance to ionic flow which characterizes the small intestinal epithelium.

The functional and structural characteristics of the ileal remnant of rat intestine were examined four weeks after 45%, 70% or 95% proximal resection. The increase in villus height in the ileal remnant had alfread reached its maximum after a resection of 45%, whereas a further increment in the length of the crypts occurred after 70% resection. There was an increase in the number of enterocytes per unit length of villus and a rise in the DNA content per unit weight of mucosal scrapings, which testifies to the development of mucosal hyperplasia in this situation. The specific activities of sucrase, measured biochemically, and of nonspecific esterase, determined histochemically, were reduced in proportion to the extent of the resection. Similarly, the uptakes of L-phenylalanine and of beta-methyl-D-glucoside by intestinal rings in vitro were progressively diminished in the ileal remnant. There was an increase in the rate of disappearance of glucose from a perfused loop in vivo, when expressed in terms of unit intestinal length. Galactose absorption remained unchanged, but when expressed in terms of unit dry tissue, was significantly reduced, in agreement with the diminished transport of both amino-acids and monosaccharides in vitro.

Two branched decaglycosylceramides, apparently identical to those identified in the small intestine of adult rats [Breimer ME, Falk K-E, Hansson GC, Karlsson K-A (1982) J Biol Chem 257:50–59], were absent during the three weeks following birth. They appeared abruptly at around 21 days. After their appearance, their tissue concentration and their base composition did not change during development. Their fatty acids were non-hydroxylated and the percentage of C22–C24 fatty acids, which was low at 24 days, increased and reached 48.6% by 27 days.

Until recently prostaglandin (PG) synthesis in the intestine under the influence of cholera and other toxins has been studied only with respect to PG of types E and F. It has recently been found that different types of PG (PGI2, PGD2, TXA2-thromboxane, and other biologically active metabolites of arachidonic acid), found previously in other tissues [4], are normally synthesized in the intestine.

Glutamine has been reported to be a major oxidative substrate in adult rat small intestine. The significance of glutamine by developing rat jejunal tissue slices and isolated mitochondria was determined. Jejunum slices from suckling rats actively oxidized glutamine at rates significantly greater than adult slices. Increasing the glutamine concentration (0.5-4 mM) in the assay increased glutamine by jejunum of suckling pups by 30% compared to a 100% increase in adult jejunum. Glutamine oxidation by isolated jejunal mitochondria was similar in suckling and adult rat. Glutamine oxidation by jejunum of suckling rat was increased in the presence of 5 mM glucose whereas adult glutamine oxidation was not affected by exogenous glucose. Glutamine inhibited glucose oxidation by jejunum of both suckling and adult rats. In adult jejunal homogenates alanine aminotransferase activity was 2-fold greater than in suckling animals. In the presence of 10 mM aminooxyacetate, a known inhibitor of alanine aminotransferase, glutamine oxidation by jejunum of suckling rat was inhibited by 95%, suggesting that alanine aminotransferase is a major metabolic pathway for the oxidation of glutamine.

Blood group A-active glycosphingolipids of the small intestine, A-6 and A-12, which have been characterized previously in the adult rat [Breimer ME, Hansson GC, Karlsson K-A, Leffler H (1982) J Biol Chem 257:906–12], were found to appear during postnatal development, using immunostaining on thin layer chromatograms with two monoclonal anti-A antibodies, A005 and A581. In this system, A005 was found to be specific for the A determinant based on the type 2 chain, while A581 reacted mainly with the A determinant based on the type 1 chain and only weakly with the A determinant based on the type 2 chain. A-6 Type 1 was detected first at 18 days after birth. Its concentration increased markedly during the fourth week. A-6 Type 2 was detected, at a very low level, in neonates. Its concentration increased between days 15 and 20 and then decreased almost to the neonate level by 28 days. Dodecaglycosylceramide A-12 followed the same pattern of reactivity as A-6 type 1 with A581, and remained strongly reactive with A005 after 20 days. Linear A-6 and branched A-12 appeared simultaneously. Antibodies directed against blood group H determinants based on the type 1 or type 2 chains did not detect any H structure which might have appeared as a precursor of either A-6 or A-12 at the early stages of postnatal development.

A histochemical study of alkaline phosphatase in heterolysosomes (demonstrated by their content of acid phosphatase and β-glucuronidase) is described in the endocytizing epithelia of the neonate rat small intestine. The possible origins and functional significance of the enzyme in these organelles is discussed.

Intra-peritoneal injections of 15 mg of B-mercaptoethylamine in rats, with an average weight of 200 g, protect the small intestine against a local irradiation of 500 r on the antero-upper portion of the abdomen.

1/7 part of small intestine was resected in 25 white rats in its superior portion. Intestines of rats reacted in 10–30 days after the operation by increased number of mitoses in response to unconditioned and conditioned food stimuli (as in normal condition). On the 60th day after the operation, the number of mitoses in the intestine of fasted operated rats was increased in comparison with fasted animals which were not operated, as well as in comparison with fasted operated rats, which were sacrificed earlier. Mitosis was still pronounced in the intestine of operated rats in 90 days after intestinal resection.

The inhibitory action of L-leucine on the intestinal absorption of D-glucose and D-galactose, as well as the inhibitory action of D-galactose on the absorption of L-leucine at various concentrations by rat small intestine has been studied. The further effect was more clearly evidenced when the medium was perfunded through the intestine in a closed circuit system using a peristaltic pump.

The study of enzyme activi ty of epi thel tocytes in macrocolon ies of the smal l intest ine developing f rom a single stern cel l has shown the i r s t r i c t ly individual functional differentiat ion, with predominance of one pa r t i cu la r enzyme in mos t colonies [1]. The dimensions of the colonies studied also var ied considerably . It was accordingly suggested that co r re la t ion may exis t between enzyme activity of the epithelium of the m a c r o colonies and the i r s ize . To tes t this hypothesis it was decided to compare the weight of t e s t colonies of epi thel iocytes and the act ivi ty of ce r ta in enzymes concerned with contact digestion of the cel ls of these colonies, in o rde r to identify any possible re la t ionship between the degree of enzyme different iat ion of the rnacrocolonies and the i r s ize .

The effects of feeding single doses of β-sitosterol, campesterol and stigmasterol on cholesterol concentration in the rat small intestine was studied to clarify their roles in cholesterol absorption. The different plant sterols affected free and ester cholesterol concentrations differently in the different intestinal segments suggesting that they have different effects on such intestinal processes as uptake, esterification and possibly synthesis of cholesterol and transport of cholesterol esters out of the mucosal cells into the lymphatics.

Chronic administration of alcohol to well-nourished rats led to striking changes in the small intestinal cell population. The present experiments corroborate the view that alcohol is directly toxic to the small intestine.

We have suggested previously that the histamine-diamine oxidase system is involved in cell proliferation. Therefore, the diamine oxidase activity and the histamine content were studied during mucosal proliferation induced by 70% resection of the small intestine of the rat with and without aminoguanidine (AG), a specific inhibitor of diamine oxidase (DAO). The DAO activity underwent a marked alteration during the period of mucosal proliferation, probably as an expression of an antiproliferative regulation mechanism. The histamine content decreased in the proliferating mucosa. No influence of AG on mucosal proliferation could be found, which might be due to a compensatory activity of the interconversion pathway.

Jejunal transport of galactose and leucine was studied in 9--45 day-old rats by means of the everted sac technique. Maximum transport was observed in 9--10-day-old rats, but then decreased until the 22nd day, and remained unchanged from then on. There were no remarkable differences in the pattern of galactose and leucine transport over this period.

TDPase is located mostly in the proximal portion of the small intestine and its activity, like that of ALPase, decreased markedly in thiamine deficiency. The decreased enzyme activities were restored after thiamine or vitamin D3. Kinetic and other studies of the purified enzyme indicated the identity of the two enzymes.

Same circadian difference in the specific activities of sucrase and maltase was observed in the purified brush border fraction as in the crude homogenate of the mucosa of rat small intestine, suggesting that the disaccharidase rhythm is not due to the mitosis rhythm of epithelial cells.

Qo2 of jejunal rings did not differ significantly between uninfected rats and rats infected for 7 days withNematospiroides dubius. Qo2 of isolated jejunal mucosal epithelial cells was significantly greater 7 days after infection than in uninfected controls or at 29–36 days after infection.

In previous studies, an oral rehydration solution containing glycine (gly) and a glucose polymer performed better than WHO–ORS in reversing water secretion in an animal model of secretory diarrhoea. We have now assessed the relative contribution of gly and glucose (glu) concentration and osmolality (osm) to the efficacy of oral rehydration solutions (ORS). After exposure to pure cholera toxin, whole rat small intestine was perfused in situ with 7 different ORS. All ORS derived from a basic solution (BORS) containing Na 50, K 25, Cl 75 and glu 50 mM, to which 25 or 50 mM of either gly, glu or mannitol was added. All ORS reversed water secretion to absorption with varying efficacy. Maximum water absorption was obtained with BORS (161±10 μl/min/g dry wt). When osm of BORS was raised to 225 and 250 mOsm/Kg by adding mannitol, water absorption decreased significantly (106±5 and 44±4 respectively, p

Studies were undertaken to assess the value of including base in ORS in (i) an animal model of intestinal secretion and (ii) children with acute gastroenteritis. After exposure to cholera toxin, rat small intestine was perfused in situ with ORG containing base or identical ORS in which base was replaced by chloride. Test solutions were WHO-ORS (Na 90, Cl 80, K 25, HCO3 30, glucose 111 mmol/1), Experimental ORS (EXP-ORS I, Na 60, Cl 55, K 25, HCO 30, glucose 111), EXP-ORS II, Na 60, Cl 55, K 25, citrate 10, glucose 111) and British National Formulary (BNF-ORS) Na 35, Cl 37, K 20, HCO3 18, glucose 200). Regarding water absorption (mean±SEM) no advantage was observed when bicarbonate was included in ORS compared with the same ORS without base. WHO-ORS (38±8 vs 40±5 μl/min/g;n=7), EXP-ORS I (98±6;n=6 vs 76±7;n=6), or BNF-ORS (19±4 vs 2.2±7;n=12). Similarly, EXP-ORS II with citrate was not superior to the citrate-free ORS.

Recent reports of the use of organ culture of animal foetal small intestine to detect cereal toxicity have proposed its use for screening the toxicity of cereal peptides for coeliac mucosa. Sane authors have assessed toxicity using morphological means, others by more objective biochemical means; the results have been variable. We have used foetal rat small intestine organ cultures to test the toxicity of gluten fraction III (GFIII), assessing the effect by morphological and biochanical means. Small intestinal segments from 18-day old rat foetuses were used and ware obtained fron several foetuses in one litter for each experiment. They were cultured with and without GFIII for 48 hours. Segments before and after culture were observed histologically and significantly more developed definite tall villi after culture in the absence of GFIII (p = 0.009), associated with significantly less stratification (p = 0.014) and more colimnar epithelial cells (p = 0.024). Alkaline phosphatase activity fell during culture, whereas α-glucosidase activity increased but there was no difference whether GFIII was present or not. Gluten toxicity for foetal rat intestine was detected using morphological, but not biochemical, means. Morphological assessment was difficult however, due to considerable variability within sections. We do not consider this type of culture to be sufficiently reliable for routine investigation of cereal toxicity, and advise caution in the interpretation of the results.

Rats were killed on day 0 and after 3, 7, 10 and 14 days of TPA, isocaloric rat chow feedings(IC), or starvation. In each group the small intestine was removed for determination of its total weight(TW), mucosal weight(MW), mucosal protein(MP), mucosal DNA, and mucosal glycolytic enzyme activities. Both TPA and IC rats were in positive N balance; weight gains were 5 and 3.5gm/d, respectively. Starved rats lost 10 gm/d. In IC rats, none of the variables changed significantly over 14 days. In TPA rats, both TW and MW decreased by 40% within 3 days, after which no further changes occurred. Both mucosal protein and DNA of TPA rats were 40% lower by 3 days and remained at this level. TW and MW of starved rats decreased by 63% over 10 days, while both mucosal protein and DNA decreased 65%. In contrast to the changes during TPA, all variables fell continuously, during starvation. Mucosal Protein: DNA ratios remained constant in all groups, suggesting a decrease in the total number of cells. Specific activities of pyruvate kinase and both fructose-1-phosphate and fructose-1,6-diphosphate aldolases remained constant in all 3 groups, but because of decreased mucosal protein and DNA contents, total intestinal activity of all enzymes was significantly decreased. These findings show that although increases in body weight can be achieved with TPA, it does not adequately maintain intestinal cell mass.

TRANSPORT processes in the small intestine are dependent on energy which suggests the participation, directly or indirectly, of adenosine triphosphate (ATP). No evidence has, however, been produced that exogenous ATP can influence intestinal transport processes, which may well result from the difficulty of getting the unstable ATP molecule to the correct place in the cellular organization before its hydrolysis occurs. A way around this difficulty is offered by the study of electrical potentials in the intestine, which are known to be associated with intestinal transfer of various substances. Potential changes can be measured within a few minutes of setting up the intestinal preparation, and appear within seconds after addition of transferable substances. They therefore appear to offer an ideal method for studying the effect of ATP on intestinal transfer.