Biomedical subjects

M Montagnani

Publications and source records attributed to M Montagnani.

At least 19 recordsLinked to original sources

PubMed2000

Effects of erythromycin on human colonic circular muscle in idiopathic chronic constipation.

BACKGROUND: Erythromycin has been shown to have profound prokinetic effects on the gastrointestinal tract of humans and animals, probably through its action on endogenous motilin receptors. The purpose of this study was to determine both the direct and indirect effects ('off contraction') of erythromycin and motilin on ex vivo circular muscle strips of the distal colon from patients with or without idiopathic chronic constipation (ICC). MATERIALS AND METHODS: Cumulative concentrations of erythromycin (1-20 microM) and motilin (0.05-1 microM) were tested in both control and ICC preparations in order to evaluate the direct drugs effect. A range doses of both erythromycin (0.5-10 microM) and motilin (0.05-0.5 microM) were tested on their ability to affect the off-contraction that follows the typical inhibitory response evoked by low frequencies of Electrical Field Stimulation (EFS) (1-5 Hz, 20 V, 1 msec pulse trains lasting 1 min). RESULTS: The direct effect of both erythromycin and motilin was a slight increase (less than 10% of the maximal ACh-induced contraction) in the basal tension, with no dose-response relationship. The off-contraction, evoked by EFS, was not affected by drugs pretreament in control preparations. Conversely, in ICC preparations both drugs significantly increased the off-contraction (about 30%). CONCLUSIONS: Erythromycin causes mainly an indirect contractile effect in circular muscle strips from ICC patients. This effect may be related to the activation of inhibitory neuronal motilin receptors. This activation might potentiate NANC relaxation, proportionally increasing the circumferential reflex contraction that follows the EFS-induced relaxation.

Adult↗

PubMed1999

Functional characterization of endothelin receptors in hypertensive resistance vessels.

OBJECTIVE: The physiological and pathophysiological functions of endothelin-1 in modulating the regional blood flow of normal and spontaneously hypertensive rats (SHR) were studied in the perfused mesenteric vascular bed, a useful model for investigating resistance vessels. DESIGN AND METHODS: We used 12-week-old SHR and Wistar-Kyoto (WKY) rats. Endothelin A (ETA) receptor responsiveness was evaluated by endothelin-1 (0.2-2 mumol/l) concentration-response curves, and repeated in the presence of indomethacin and the ETA and endothelin B (ETB) receptor antagonists BQ-485 and BQ-788, respectively. ETB receptor responsiveness was tested by sarafotoxin S6c concentration-response curves, obtained in the noradrenaline-precontracted mesenteric vascular bed, and repeated after treatment with BQ-788 and after endothelial denudation. RESULTS: In both groups, endothelin-1 induced concentration-dependent contraction; SHR exhibited a markedly increased maximal effect compared with WKY rats (P < 0.01). BQ-485 produced a shift to the right for endothelin-1 concentration-response curves in both groups, with a higher pA2 (negative common logarithm of the antagonist that produces an agonist dose ratio of 2) value in SHR than in WKY rats (P < 0.01). The increase in the maximal effect produced by endothelin-1 in SHR was prevented by indomethacin, which also induced a significant increase in the endothelin-1 concentration producing the half-maximal response (EC50) in SHR (P < 0.05). Sarafotoxin S6c produced an ETB-dependent endothelium-mediated relaxant effect in WKY rats, which was not observed in SHR. CONCLUSIONS: The higher vasoconstriction induced by endothelin-1 in SHR may be related to a greater number of available ETA receptors, due to the presence of an ETA receptor subtype. This mechanism may be linked to the production of prostanoids that add to the direct endothelin-1-evoked vasoconstriction. These results, together with the lack of relaxation in response to sarafotoxin S6c in SHR, suggest that an imbalance in the endothelin-1 ability to induce both contraction and relaxation is present in SHR with sustained hypertension, manifesting as a greater contractile effect evoked in this strain.

Animals↗

PubMed1999

Long-term results with interferon therapy in chronic type B hepatitis: a prospective randomized trial.

OBJECTIVES: The aims of this long-term, prospective randomized study were to evaluate the clinical usefulness of alpha-interferon in treating chronic HBV infection and to establish whether clearance of viral replication markers and normalization of liver function tests induced by alpha-interferon were sustained. METHODS: Sixty-four patients with chronic wild type (HBeAg-positive) hepatitis B, enrolled between 1983 and 1987, were randomized into two groups. Thirty-three patients received alpha-interferon (5 MU/m2 three times weekly for 6 months; treated group), and 31 were not treated (controls). Treated and control patients were prospectively followed for a mean of 86.4 +/- 6.96 and 79.7 +/- 6.8 (p = NS) months, respectively. RESULTS: Clearance of the following viral markers was found in treated and control patients as follows: HBV-DNA, 26 (78.9%) and 18 (58.1%) (p = 0.106); HBeAg, 30 (90.9%) and 19 (61.2%) (p < 0.007); and HBsAg, 12 (36.4%) and three (9.8%) (p < 0.017). Persistent abnormal ALT levels were found in 11 (33.3%) treated and in 22 (70.9%) control patients (p < 0.025). Four control and three treated patients developed portal hypertension whereas two control and one treated patient developed hepatocellular carcinoma. Seven patients (five treated and two controls) were retrospectively found to have hepatitis C virus (HCV) coinfection before enrollment. To date, all coinfected patients remain positive for HCV-RNA. Also, all HCV coinfected patients, except one in the treated group, had persistent increased serum ALT levels. One of the coinfected patients developed portal hypertension. CONCLUSIONS: Chronic HBV hepatitis patients responding to interferon treatment had a faster, more complete, and sustained clearance of viral markers than controls; HCV coinfection does not seem to negatively affect the clearance of HBV replicative markers. However when coinfection occurs, hepatic disease persists despite HBV marker clearance.

Adolescent↗

PubMed1999

Sluggish small bowel motility is involved in determining increased biliary deoxycholic acid in cholesterol gallstone patients.

OBJECTIVE: Our aim was to establish whether small intestine transit time is defective in subjects with cholesterol gallstones. METHODS: We enrolled 10 patients (eight women, two men; mean age, 48.7 yr; mean body mass index [BMI], 22.4 Kg/m2) with recently diagnosed cholelithiasis, with no liver pathology, who were not taking any drugs, and 11 comparable healthy volunteers (eight women, three men; mean age, 46.2 yr; mean BMI, 22.7 Kg/m2), who served as controls. All subjects underwent orocecal (by starch breath test technique and serum assays of salazopyrin), oroileal (by serum assays of tauroursodeoxycholic acid), and duodenoileal (by serum assays of taurocholic acid) transit times; cholesterol saturation index; and bile acid composition and gallbladder motility studies (by ultrasound). For serum assays, blood samples were collected over a period of 7 h. Gallbladder motility and orocecal transit time were evaluated simultaneously. RESULTS: All four means of assessing transit time gave longer times in cholesterol gallstone patients than in controls: orocecal transit time (salazopyrin) = 366 +/- 13 vs 258 +/- 16 min, p < 0.0005; orocecal transit time (starch breath test) = 415 +/- 139 vs 290 +/- 15 min, p < 0.01; duodenoileal transit time: 272 +/- 23 vs 205 +/- 23 min, p < 0.03; and oroileal transit time: 308 +/- 18 vs 230 +/- 19 min, p < 0.009. Cholesterol gallstone patients showed an increase in percent molar biliary deoxycholic acid (30% +/- 4.5% vs 16% +/- 1.3%, p < 0.02) and a decrease in percent molar cholic acid 32% +/- 2.2% vs 40% +/- 1.3%, p < 0.03) and chenodeoxycholic acid (34% +/- 3% vs 41% +/- 1.8%, p < 0.03), compared with controls; patients also had greater percent molar biliary cholesterol. A linear relationship (r2 = 0.6324, p = 0.0012) between biliary deoxycholic acid and small bowel transit time was found. Residual gallbladder volumes were larger in cholesterol gallstone patients (11.38 +/- 1.27 vs 7.55 +/- 0.39 ml, p < 0.04), whereas basal gallbladder volumes, although higher, did not reach statistical significance (24.25 +/- 2.41 vs 19.98 +/- 1.63 ml; p = ns). CONCLUSIONS: This study confirms that patients with cholesterol gallstones have delayed small bowel transit, defective gallbladder motor function, and increased biliary deoxycholic acid. Delayed small bowel transit may contribute to supersaturation of bile with cholesterol by increasing deoxycholic acid production.

Bile↗

PubMed1999

Specific antibodies reactive with the 22-kilodalton major outer surface protein of Borrelia anserina Ni-NL protect chicks from infection.

An outer surface lipoprotein of 22 kDa was identified in the avian pathogen Borrelia anserina Ni-NL by using antibody preparations reactive with bacterial surface-exposed proteins. Amino acid sequence analysis of the 22-kDa protein demonstrated 90% identity with VmpA of B. turicatae, suggesting that the protein belongs to the family of 20-kDa outer surface proteins of the genus Borrelia. All of the 60 chicks intramuscularly treated with antibodies specifically reacting with the 22-kDa protein and infected with strain Ni-NL were completely protected from infection, since no spirochetemia was detected, and from death. Control chicks were treated with immune sera raised against apathogenic strain B. anserina Es, which expresses a prominent 20-kDa polypeptide that is also a member of the Vmp family but does not cross-react immunologically with the 22-kDa protein of the Ni-NL strain. These animals, infected with B. anserina Ni-NL, showed a high degree of spirochetemia 10 days after infection, and all died between 14 and 21 days after infection. The results showed that the 22-kDa surface protein of B. anserina Ni-NL is a determinant of the pathogenic potential of the strain and also confirmed that only strain-specific antibodies are protective against B. anserina infection.

Amino Acid Sequence↗

PubMed1998

Cholinergic stimulation and nonadrenergic, noncholinergic relaxation of human colonic circular muscle in idiopathic chronic constipation.

The aim of our study was to further investigate the pathophysiological mechanism underlying idiopathic chronic constipation (ICC), a disorder of colonic motility. A possible alteration of excitatory and inhibitory neurotransmission and also the role of inhibitory neurotransmitters such as nitric oxide (NO), 5'-adenosine triphosphate (ATP), and vasoactive intestinal peptide (VIP) has been evaluated on preparations of distal colon from patients with or without ICC. The isometric tension was recorded from isolated circular muscle strips of both experimental groups during pharmacological and electrical field stimulation (EFS). The contractile response obtained by acetylcholine (ACh 20 microM), EFS (20 Hz, 20 V, 1 msec, pulse trains lasting 1 min) and substance P (SP 1 microM) was significantly lower in ICC than in control preparations. The effect of inhibitory nonadrenergic, noncholinergic innervation was evaluated using EFS at low frequencies (0.5-8 Hz), after cholinergic and sympathetic blockade with atropine (3 microM) and guanethidine (3 microM). The maximum relaxation value expressed as percentage of inhibition of SP-induced contraction was significantly higher in ICC than in control preparations (87+/-2.4 and 67+/-6.3, respectively; P<0.05). Experiments with substances that antagonize or reduce the effect of putative inhibitory mediators (VIP 6-28, apamin and N(G)-nitro-L-arginine) suggest that an alteration in NO and ATP release is present in ICC preparations. In particular at a higher inhibitory frequency NO-mediated relaxation is enhanced in ICC vs control, supporting the hypothesis that excessive NO production may be involved in pathophysiological mechanism of constipation.

Acetylcholine↗

PubMed1998

Functional evaluation of 5-hydroxytryptamine receptor activity in rat resistance vessels.

1. To characterize 5-hydroxytryptamine (5-HT) receptors in rat perfused mesenteric vascular bed (MVB), the effect of 5-HT and related compounds was investigated by functional assay. 2. In quiescent preparations, 5-HT elicited a concentration-dependent conctractile response. After addition of ketanserin, a 5-HT2 receptor antagonist, EC50 values were significantly higher than in controls. 3. In noradrenaline (NA)-precontracted preparations, under continuous infusion of ketanserin, 5-HT, 5-carboxamidotryptamine (5-CT) and sumatriptan produced relaxation. Their rank order of relaxant potency and maximum effect were sumatriptan > 5-HT > 5-CT. Methysergide (1 microM) and spiperone (20-100 nM) caused a rightward shift of the relaxation curve to sumatriptan. These data suggest that vasodilatation in rat MVB is mediated by an 'atypical' subtype of 5-HT1-like receptor, which reveals a pharmacological profile similar to that of the 5-HT1D receptor. The involvement of both 5-HT3 and 5-HT4 receptors can be ruled out, since tropisetron (up to 10 microM) was not able to antagonize the relaxant effect by sumatriptan. 4. Under granisetron infusion (3 microM), the contractile response evoked by perivascular nervous stimulation, but not exogenous NA contraction, was significantly reduced (P < 0.001). These data demonstrate the presence of 5-HT3 receptors in peripheral neurones, modulating neurotransmitters release.

Animals↗

PubMed1998

New insights in the physiology and molecular basis of the intestinal bile acid absorption.

Intestinal bile acid absorption is a fundamental step in the enterohepatic circulation and metabolism of these endogenous compounds. The physiology of the active, sodium coupled transport system for bile acids in the terminal ileum has been extensively studied and characterized. Structure-activity studies have elucidated the requirements for the ileal transport system, and studies with photolabile bile acid derivatives identified the putative ileal bile acid transport proteins. Characterization of the functional sites of the transport system elucidated some of the possible mechanisms which allow the interaction of bile acids and sodium ions with the ileal transporter. Considerable progress has been made during recent years, after the ileal apical and cytosolic bile acid transport proteins have been cloned and characterized. The role of point mutations in bile acid malabsorption has been studied, and the knowledge of the amino acid sequence of the transport proteins will be of help in the investigation of the transport mechanisms.

Animals↗

PubMed1996

Acanthocytosis, retinitis pigmentosa, pallidal degeneration. Report of two cases without serum lipid abnormalities.

We describe two unrelated patients with Hallervorden-Spatz, disease characterized by prominent facio-bucco-lingual dyskinesia. Acanthocytosis and retinitis pigmentosa were additional findings. Brain MRI showed the typical 'tiger's eye' image of the globus pallidus. This phenotype closely resembled the so-called HARP syndrome (hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa and pallidal degeneration), but extensive serum lipid study failed to demonstrate any lipoprotein abnormality. Our results raise the question whether HARP syndrome is an autonomous entity or a particular phenotype of Hallervorden-Spatz disease.

Acanthocytes↗

PubMed1996

Hyporeactivity of mesenteric vascular bed in endotoxin-treated rats.

Vascular reactivity and activation of the nitric oxide (NO) pathway were investigated in perfused mesenteric vascular bed removed from rats 5 h after i.p. injection of bacterial lipopolysaccharide (E. coli lipopolysaccharide, 30 mg kg -1). Lipopolysaccharide treatment induced hyporesponsiveness to noradrenaline. Maximal noradrenaline-induced vasoconstriction was significantly reduced in lipopolysaccharide-treated vs. untreated preparations. Continuous infusion of L-arginine (L-Arg) (0.2 mM) enhanced noradrenaline hyporeactivity of lipopolysaccharide-treated rats. N omega-Nitro-L-arginine methyl ester (L-NAME) (0.2 mM), a non-selective inhibitor of NO synthase, failed to completely restore the noradrenaline hyporeactivity of lipopolysaccharide-treated + L-Arg-infused mesenteric vascular bed. After L-NAME treatment. Methylene blue (10 microM), a guanylate cyclase inhibitor, produced no additional increase of noradrenaline vasoconstriction in lipopolysaccharide-treated + L-Arg-infused mesenteric vascular bed, suggesting that an NO-independent activation of guanylate cyclase may be excluded. In lipopolysaccharide-treated preparations, L-Arg (0.2 mM) elicited a significant increase in nitrite production, which was antagonized by L-NAME. In conclusion, lipopolysaccharide-induced noradrenaline hyporesponsiveness of rat resistance vessels can only be partially explained by NO overproduction. Other mechanisms, probably related to vasoconstriction, may be involved.

Animals↗

PubMed1996

Prenatal exposure to carbon monoxide and vascular responsiveness of rat resistance vessels.

The aim of the present study was to investigate the influence of prenatal exposure to carbon monoxide (CO) on vascular reactivity of rat resistance vessels, in different stages of neurogenesis. Both prenatally CO-exposed and control male Wistar pups (5-7, 9-11, 14-16, 20-22 days) were tested vs respective 60 day adult rats. The results showed that: (i) at 5-7 days of age, TTX caused a more marked inhibition of perivascular nerve stimulation (PNS)-evoked vasoconstriction in CO-exposed animals with respect to controls; (ii) the NO-related relaxant effect by ACh in CO-exposed group appeared earlier (5-7 days) than in control group (9-11 days); (iii) the contractile response evoked by ACh on resting tone disappeared earlier (after 14-16 days) than in control group (after 20-22 days). These observations suggested that CO-exposure might induce changes in nerve electrophysiological properties and might cause a precocious maturation of the NO-related enzymatic mechanism implicated in ACh-relaxation.

Acetylcholine↗

PubMed1996

Species differences in hepatic bile acid uptake: comparative evaluation of taurocholate and tauroursodeoxycholate extraction in rat and rabbit.

Dose-response curves for taurocholate and tauroursodeoxycholate were performed in rat and rabbit livers to get more insight into species differences in the hepatic bile acid uptake. The bile acids showed saturation kinetics in both animals, the Vmax in rat being higher than in rabbit and the Km being lower in the rat than in the rabbit for both the bile acids, with no significant difference in the hepatic cells morphometric parameters. Therefore, it is possible that differences in the kinetic parameters are related to the number and, to a lesser extent, to the affinity of the transporters on the sinusoidal plasma membranes.

Animals↗

PubMed1996

Relationship between structure and intestinal absorption of bile acids with a steroid or side-chain modification.

UNLABELLED: A structure-activity relationship for bile acid (BA) intestinal absorption is known to exist. To better understand the BA structural requirements for optimal BA intestinal absorption, rabbit ileal perfusion studies were performed. Unconjugated BA: Ursodeoxycholic (UDCA) and ursocholic acid (UCA) with methyl (6MUDCA and 6MUCA) or fluoro group (6FUDCA and 6FUCA) in the 6 position and UCA with a methyl group in 23 position (23MUCA) were compared with unconjugated UDCA, UCA, deoxycholic (DCA), chenodeoxycholic (CDCA), hyocholic (HCA), and hyodeoxycholic (HDCA) acid. BA lipophilicity was evaluated by their octanol-water partition coefficient. Conjugated BA: Taurine-conjugated UDCA and UCA with a methyl group in the 23 position (T23MUDCA and T23MUCA) were compared with the corresponding taurine-conjugated natural analogs. An analog of glycine-conjugated UDCA with the C24 amide bond replaced by a -CO-CH2- in the 24 position (24PUDCA) was studied and results were compared with the natural form (GUDCA). Unconjugated BA absorption was dose dependent (i.e., passive) and followed their lipophilicity: DCA > 6MUDCA > CDCA > HDCA > UDCA > HCA > 6FUDCA > 6MUCA > 6FUCA > UCA. Conjugated BA absorption was active, and Vmax was in the following order: TCA > TUDCA > TUCA > T23MUCA > T23MUDCA > 24PUDCA > GUDCA. 24PUDCA transport was also active and higher than GUDCA. CONCLUSION: Passive transport is dependent on BA lipophilicity. Conjugated BAs are actively transported, and the presence of a 23-C methyl group does not improve transport when compared with the natural analogs. The substitution of the C24 amide bond with a -CO-CH2-still affords interaction of the BA with the intestinal transport carrier.

Animals↗

PubMed1996

Intestinal absorption of bile acids in the rabbit: different transport rates in jejunum and ileum.

BACKGROUND & AIMS: A direct comparison of jejunal and ileal absorption rates of bile acids has not been reported. The aim of this study was to compare the relative transport rates of different bile acids in the jejunum and ileum. METHODS: Jejunal and ileal rabbit intestinal segments were separately perfused with bile acid solutions, and dose-response curves were obtained for taurocholate, ursodeoxycholate, chenodeoxycholate, deoxycholate, and their glycoconjugates. Membrane fluidity and bile acid transport were assessed in brush border membrane vesicles. RESULTS: Taurocholate showed active transport in the ileum and no transport in the jejunum. Unconjugated bile acids showed passive diffusion in the two tracts, whereas glycoconjugated bile acids showed both components of transport in the ileum and passive diffusion in the jejunum (lower in the latter). A higher membrane fluidity and lower cholesterol-to-phospholipid ratio were found in the jejunum. Ursodeoxycholate reduced bile acid uptake into membrane vesicles from both ileum and jejunum. CONCLUSIONS: Active transport is limited to the ileum. Passive diffusion is higher through a less fluid membrane with a higher cholesterol-to-phospholipid ratio in the ileum than in the jejunum. Ursodeoxycholate inhibition may be at the level of a facilitated, sodium-independent diffusion in the jejunum.

Animals↗

PubMed1996

Postnatal developmental changes of receptor responsiveness in rat mesenteric vascular bed.

1. The response to perivascular nervous stimulation (PNS) and the responsiveness to receptor agonists, in different stages of neurogenesis, on rat mesenteric vascular bed (MVB), was investigated. Rats of different age groups (5-7, 9-11, 14-16, 20-22 days) were tested, using 60-day-old rats as controls. 2. In the 5-7 days age group, the response to PNS was resistant to TTX treatment (1 x 10(-6) M). The TTX inhibition increased with age and became almost complete in 60-day-old rats. 3. In the 1st week of postnatal life (pre-innervation period), noradrenaline (NA) and 5-hydroxytryptamine (5-HT) produced contraction, whereas isoprenaline (ISO) and dopamine (DA) caused relaxation. During the 1st and 2nd week, pD2 values of NA and ISO were significantly higher than in adult control rats. No significant difference in pD2 values of 5-HT and DA was observed during postnatal development. 4. At 5-7 days, the relaxation by acetylcholine (ACh), typical of adult age, was absent and ACh evoked only contractile responses. The relaxant effect by ACh appeared at 9-11 days, increased with age and, by the end of the 2nd week, did not differ from that of the adult group. 5. These results provide evidence that responsiveness of all tested receptors in the MVB is already present in the pre-innervation period (1st week). Adrenergic receptor responsiveness is higher at birth and decreases by the end of the 3rd week of postnatal life, when connections between the central nervous system and effector organs are established. Only muscular muscarinic receptors, responsible for ACh-induced contraction, are functional in the 1st week, while endothelial muscarinic receptors, responsible for ACh-induced relaxation, become gradually responsive later in postnatal life.

Acetylcholine↗

PubMed1996

Uptake and killing of Lyme disease and relapsing fever borreliae in the perfused rat liver and by isolated Kupffer cells.

In situ-perfused rat livers were infused with a single dose of 1.5 x 10(7) radiolabeled borreliae. Significant (P < 0.00005) differences in the liver uptake of the agents of Lyme borreliosis, Borrelia burgdorferi IRS, Borrelia afzelii VS461, and Borrelia garinii PBi, and that of the agents of relapsing fever, Borrelia hermsii, Borrelia parkeri, and Borrelia turicatae, were observed. The liver uptakes ranged between 65.9% for B. burgdorferi IRS and 40.5% for B. turicatae. Neither relapsing fever nor Lyme disease borreliae were recovered from infected livers when the livers were cultured in Barbour-Stoenner-Kelly II medium. The in vitro uptake of B. burgdorferi IRS by isolated rat Kupffer cells was rapid, and within 30 min of the infection, large intracellular aggregates of amorphous material were detectable by immunofluorescence with specific anti-B. burgdorferi antibody. The reculturing of B. burgdorferi IRS from Kupffer cells incubated for 24 h in RPMI medium before inoculation with bacteria was negative. The results obtained in this study indicated that borreliae are efficiently taken up and killed by rat hepatic macrophages in the absence of serum factors.

Animals↗

PubMed1996

Beta-adrenoceptor responsiveness of splenic macrophages in normotensive and hypertensive rats.

The aim of the present study was to investigate putative mechanisms implicated in the impaired phagocytic response of spontaneously hypertensive rats (SHR)1. The effect of in vitro treatment with isoproterenol (ISO), a beta-adrenergic drug, on phagocytosis and respiratory burst by splenic macrophages (SpMø) from normotensive Wistar-Kyoto rats (WKY) and SHR with established hypertension, respectively, was evaluated. Furthermore, the relaxant effect of ISO was determined in phenilephrine-precontracted thoracic aorta strips from SHR compared with age-matched WKY rats. Results indicate that exposure of rat SpMø to ISO generate a significant and dose-dependent reduction of phagocytosis and oxidative burst which was antagonized, almost completely, by the beta-adrenergic antagonist propranolol (PRO). Unlike normotensive, in hypertensive rats treatment with ISO fail to modulate phagocytosis and respiratory burst activity by SpMø. At vascular level, aortic relaxation by ISO was reduced in SHR when compared to WKY rats. These findings suggest that SHR exhibit changes not only in vascular, but also in macrophage beta-adrenoceptor-mediated responses. It is postulable that sympathetic overactivity could be responsible for impaired phagocytic functions and beta-receptor alterations observed in SHR.

Animals↗

PubMed1995

Bile acid structure and intestinal absorption in the animal model.

A close structure-activity relationship exists between the transport of bile acids (BA) in the liver and intestine; hepatic and intestinal BA transport can be evaluated and compared by using perfused liver and perfused intestine in the rabbit. The passive intestinal absorption is limited to the unconjugated BA, which occurs throughout the small bowel and colon, and is conditioned by the apical membrane lipid composition. A higher diffusion component is found in the terminal ileum compared to the jejunum, and seems to be related to the higher cholesterol-to-phospholipid ratio of the ileal brush border membranes. The active transport system is well characterized and the brush border membrane receptor, cytosolic BA binding proteins and basolateral anion exchange protein have been identified. Recently, the ileal BA transporter has been cloned from the hamster and human ileum and the main cytosolic BA binding protein was cloned from the rat ileum. In the liver, the active transport predominates on the passive diffusion both for conjugated and unconjugated BA. The maximal transport capacity in the liver is tenfold higher than in the intestine, while the Km values are of the same order of magnitude, i.e. in the millimolar range. Neither system operates at its maximum transport rate with prevalent concentrations of BA in portal blood or luminal content.

Animals↗