Biomedical subjects

E Arilla

Publications and source records attributed to E Arilla.

At least 55 records · Page 3Linked to original sources

PubMed1994

G proteins in rat liver proliferation during cholestasis.

Liver proliferation appears to be dually regulated, in part by cyclic AMP levels. Here we studied the alterations in the stimulatory action of cholera toxin and other agents on the adenylyl cyclase system, as well as the status of Gs and Gi protein subunits during the liver proliferation that follows bile duct ligation in rats. The stimulatory effects of glucagon and vasoactive intestinal peptide (which act through membrane receptors) or guanosine 5'-[beta gamma-imido]triphosphate (which interacts with G proteins) and forskolin (which directly activates the adenylyl cyclase catalytic subunit) on liver adenylyl cyclase activity were blunted in cholestasis. The results indicated an impairment in the stimulatory interaction between the alpha s subunit of Gs protein and the adenylyl cyclase catalytic subunit. Indeed, we observed an important decrease in the stimulation of adenylyl cyclase activity by cholera toxin in cholestasis that was accompanied by a reduced extent of [32P]ADP ribosylation of alpha s protein catalyzed by cholera toxin, as revealed by the poor labeling of the 42,000 Da band in liver membranes from cholestatic rats. However, there was no change in the amount of alpha s or beta proteins as measured with immunoblotting techniques. Experiments on [32P]ADP ribosylation of alpha i subunits of Gi proteins indicated an impairment in liver membranes from cholestatic rats, whereas Western blotting for the detection of alpha i subunits showed decreased alpha i3 and increased alpha i2 levels in this condition. Further efforts are needed to better understand the molecular mechanisms underlying the relationship between the observed divergent expression of Gs and Gi proteins and liver cell proliferation in the cholestatic liver.

Adenosine Diphosphate↗

PubMed1994

Serum gastrin level and gastric somatostatin content and binding in long-term pyloromyotomized children.

Since somatostatin inhibits basal and stimulated gastric acid secretion and gastrin release, it is conceivable that decreased gastric somatostatin concentration may be one of the factors responsible for gastric hypersecretion found in patients who have undergone long-term pylorotomy for hypertrophic pyloric stenosis. To investigate this proposal the somatostatin-like immunoreactivity concentration was determined in antral and fundic mucosa samples from control and long-term pyloromyotomized children. In addition, somatostatin binding to cytosol from gastric (fundus and antrum) mucosa and fasting serum gastrin levels and serum gastrin response to a standard breakfast were also studied. The mean fundic and antral somatostatin-like immunoreactivity concentrations were significantly lower in long-term pyloromyotomized children than in control children. The depletion of fundic and antral somatostatin-like immunoreactivity content was associated with an increase in the number of gastric somatostatin binding sites. The fasting serum gastrin levels and serum gastrin response to a standard breakfast (after 60 min) in long-term pyloromyotomized children was significantly higher than those in control children. Since, together with the increase of somatostatin binding to gastric mucosa, there is an increase in the gastrin serum levels, despite the inhibitory effect of somatostatin on gastrin release, the binding capacity cannot be the main factor determining the response to somatostatin in long-term pyloromyotomized children. The present results suggest that both somatostatin and gastrin have some pathophysiologic importance in long-term pyloromyotomized children.

Adolescent↗

PubMed1994

Effect of sulpiride on somatostatin receptors, somatostatin-like immunoreactivity and modulation of adenylyl cyclase activity in the rat brain.

The present study investigates the effects of the administration of an intracerebroventricular (i.c.v.) dose of 500 micrograms/rat of the neuroleptic (-) sulpiride on somatostatin-like immunoreactivity (SSLI) levels, 125I-Tyr11-SS binding to its specific receptors, SS-modulated adenylyl cyclase (AC) activity and the pertussis toxin (PTX) substrates measured by toxin-catalysed ADP ribosylation of the alpha-subunits from G-proteins. (-) Sulpiride significantly decreased the SSLI levels in the frontoparietal cortex at 30 min but was without effect on the SSLI concentration in the striatum. This decrease had disappeared within 24 hr. The administration of (-) sulpiride produced a significant increase in the number of 125I-Tyr11-SS receptors and a significant reduction in their affinity at 30 min after injection in the striatum without affecting the frontoparietal cortex. The effects of the (-) sulpiride injection had disappeared after 24 hr. This change in SS binding was not due to a direct effect of (-) sulpiride on these receptors since no effect on binding was produced by high concentrations of (-) sulpiride (10(-5) M) when added in vitro. No significant differences were seen in either brain region for the basal or the forskolin (FK)-stimulated AC enzyme activities in the control and (-) sulpiride groups. In the (-) sulpiride group, the capacity of SS to inhibit FK-stimulated AC in the frontoparietal cortex was significantly higher than in the control group with no significant difference in the striatum.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate Ribose↗

PubMed1994

Somatostatin receptors coupled to the inhibition of adenylyl cyclase in the rat frontoparietal cortex are modulated by alpha 2 adrenoceptors.

The administration of an alpha 2-adrenoceptor agonist, clonidine, increased the number of somatostatin (SS) receptors and the affinity constant in frontoparietal cortex membranes. In addition, in the clonidine group, the capacity of SS to inhibit basal and forskolin (FK)-stimulated adenylyl cyclase (AC) activity in the frontoparietal cortex was significantly higher than in the control group. Pretreatment with the alpha 2-adrenoceptor antagonist yohimbine prevented the clonidine-induced changes in SS binding and SS-inhibited AC activity. Yohimbine alone had an opposite effect from clonidine. These experiments provide further evidence that the alpha-adrenergic system modulates the rat frontoparietal cortex somatostatinergic system.

Adenosine Diphosphate Ribose↗

PubMed1994

VIP receptor/effector system in liver membranes from cholestatic rats.

A reduced efficacy of VIP (43% of the control) without modification in its potency (ED50 = 2.2 nM) was observed in regenerating rat liver after cholestasis (bile duct ligation). The same occurred with glucagon-stimulated adenylyl cyclase activity because the efficacy of this VIP-related peptide was also reduced (53% of the control) without changes in its potency in this experimental model. The equilibrium binding data revealed no changes in either the affinity or the VIP binding capacity of liver membranes during cholestasis. Cross-linking experiments gave the same apparent molecular mass for the liver VIP-receptor complex (52 kDa) in control and cholestatic rats. The coupling between the VIP receptor and the Gs-protein was also unaffected because the sensitivity of VIP binding to GTP did not change after bile duct ligation. However, liver membranes from cholestatic rats showed a low extent of both ADP-ribosylation of the Gs-protein alpha subunit (as assessed with cholera toxin) and adenylyl cyclase stimulation by a direct effector such as forskolin. Thus, VIP-stimulated adenylyl cyclase activity is decreased in regenerating liver after cholestasis due probably to an impairment in the interaction between Gs-protein and adenylyl cyclase as well as a defect in the enzyme itself.

Adenylyl Cyclases↗

PubMed1993

Effects of sensitization on vasoactive intestinal polypeptide-induced relaxation and its concentration and binding in guinea-pig airways.

We investigated the relaxant effect of vasoactive intestinal polypeptide (VIP) in trachea and lung parenchyma from normal and sensitized guinea-pigs. A technique by which drug access was restricted to either the mucosal or the adventitial surface of tracheal rings was used. In intact trachea, concentration-response curves for VIP entering from the mucosal surface (pD2 = 6.61 +/- 0.06) were displaced to the right compared with those for adventitial entry (pD2 = 6.78 +/- 0.04). Epithelium removal produced a leftward shift (approximately 2.8-fold) in the mucosal VIP concentration-response curve. Sensitization did not alter the responsiveness (maximal effect) or sensitivity (pD2 values) of tracheal rings to VIP irrespective of the surface of drug entry and of the absence or presence of epithelium. VIP-induced relaxation of normal and sensitized lung strips was also similar. Sensitization resulted in a significant decrease in tracheal VIP content (from 2.16 +/- 0.07 in normal to 0.60 +/- 0.08 nmol/mg protein in sensitized trachea; P < 0.05; n = 7) whereas the affinity of both high- and low-affinity binding sites for VIP increased as compared to that of normal trachea. Differences were not found in the binding capacities of normal and sensitized trachea. VIP content and binding did not differ in normal and sensitized lung. In conclusion, immunological sensitization produced changes in VIP tracheal content and binding but neither VIP-induced relaxation of isolated airways nor the influence of epithelium in this response was altered.

Animals↗

PubMed1993

Brain somatostatinergic system at late pregnancy, parturition and the early postpartum period in the rat.

During pregnancy and postpartum rats experience a wide variety of behavioural changes. Since the somatostatinergic system has been implicated in the control of some of these changes, the present study examined somatostatin (SS) content and specific binding in the frontoparietal cortex and hippocampus of non-pregnant, pregnant (17 to 18 days), parturition and postpartum (10 and 30 days) rats as well as in ovariectomized rats which were or were not treated with estradiol valerianate. The content of somatostatin-like immunoreactivity (SSLI) was increased at 17 days of pregnancy in frontoparietal cortex and decreased at parturition and 10 days postpartum in that region and the hippocampus under study when compared with SSLI levels in non-pregnant rats. At 30 days postpartum the SSLI content returned to non-pregnant values in both brain regions. Scatchard analysis showed that the decrease in [125I]Tyr11-SS binding observed at 17 days of pregnancy in the frontoparietal cortex was due to the decrease in the number of SS receptors. In contrast, on the day of delivery the number of SS receptors in the same brain region increased. The affinity of the SS receptors was consistently unchanged in pregnant and non-pregnant rats in both regions. At 10 days postpartum the value of specific binding of the tracer to SS receptors in the frontoparietal cortex was not significantly different from that in the non-pregnant rats, although the actual number of receptors was slightly higher. Pregnancy did not change SS binding in the hippocampus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Modulation by isoproterenol and propranolol of somatostatin receptors in synaptosomes from rat frontoparietal cortex.

DL-Propranolol (PRO), a beta-adrenergic blocking agent, and the neuropeptide somatostatin (SS) have central nervous system depressant and anticonvulsive properties. To investigate a possible relationship between these two components, we studied the influence of PRO and DL-isoproterenol (ISO), a beta-adrenergic agonist, on the somatostatinergic system in the rat frontoparietal cortex. The short- (5 h) and long-term (14 days) administration of ISO (5 mg/kg, intraperitoneally (i.p.)), or of PRO (10 mg/kg, i.p.) did not affect somatostatin-like immunoreactivity (SLI) content in the frontoparietal cortex of male Wistar rats. Both short- and long-term ISO administration decreased the number of specific [125I]Tyr11-SS receptors in synaptosomes from frontoparietal cortex (31%, P < 0.05, and 26%, P < 0.02, after short- and long-term administration, respectively) without changing the affinity constant. This decrease in the number of [125I]Tyr11-SS receptors was not due to a direct effect of ISO on these receptors since no decrease in binding was produced by high concentrations of ISO (10(-5) M) when added in vitro. This decrease could be blocked by pretreatment with PRO. Short- and long-term administration of PRO alone produced an increase in the [125I]Tyr11-SS binding in frontoparietal cortex (26%, P < 0.02, and 40%, P < 0.001, after short- or long-term administration, respectively) without changing the affinity constant.

Animals↗

PubMed1993

High ammonia diet: its effect on the glial fibrillary acidic protein (GFAP).

The effect of a recent hyperammonemic model, consisting of a high ammonia diet for 3, 7, 15, 45, and 90 days, on glial fibrillary acidic protein (GFAP) in the rat spinal cord and on blood ammonia levels has been studied. The high ammonia diet was prepared by mixing a standard diet with ammonium acetate (20% wt/wt); in addition, 5 mM of ammonium acetate was added to the water supply. GFAP contents were determined by means of immunoblotting analysis. The results demonstrated that this high ammonia diet model neither induces significant changes in GFAP immunoreactivity, nor modifies total protein concentration, and only induces significant blood hyperammonemic levels in the first days of treatment. An adaptive response to the diet is suggested and discussed to explain these results. A relation between ammonia and GFAP expression is suggested because transient hyperammonemia induces transient, although no significant, changes on GFAP expression.

Ammonia↗

PubMed1993

Effect of acute and chronic diisopropylfluorophosphate and atropine administration on somatostatin binding in the rat frontoparietal cortex and hippocampus.

The acute and chronic administration of diisopropylfluorophosphate (DFP), an inhibitor of acetylcholinesterase (AChE), and of atropine, a blocker of muscarinic cholinergic receptors, did not affect somatostatin-like immunoreactivity (SLI) content in the frontoparietal cortex and hippocampus of rats. Acute and chronic DFP administration increased the number of specific 125I-Tyr11-somatostatin (125I-Tyr11-SS) receptors in synaptosomes from the frontoparietal cortex but not in those from the hippocampus and did not change the affinity constant. This increase in 125I-Tyr11-SS binding was not due to a direct effect of DFP on somatostatin (SS) receptors since no rise of binding was produced by high concentrations of DFP (10(-5) M) when added in vitro. The increase could be blocked by pretreatment with atropine. The acute administration of atropine alone had no observable effect on the number of SS receptors. However, repeated atropine administration produced a significant decrease in the 125I-Tyr11-SS binding in synaptosomes from the frontoparietal cortex but not in those from the hippocampus although the affinity constant was unchanged. The results suggest that interactions between somatostatinergic and cholinergic receptors may be important in the rat frontoparietal cortex.

Animals↗

PubMed1993

Effect of serotonin axon injury on the somatostatinergic system in rat frontoparietal cortex.

In order to investigate the possibility that, in the rat, some cerebral cortex somatostatin (SS) receptors may be localized presynaptically on the terminals of serotonergic neurons, serotonin [5-hydroxytryptamine, (5-HT)] neurons in the central nervous system were damaged with a local intracerebral injection of the serotonergic neurotoxin, 5,7-dihydroxytryptamine(5,7-DHT). The injection of 5,7-DHT (11 micrograms free base dissolved in 10 microliters of isotonic saline containing 0.01% ascorbic acid) in rats produced an reduction by about 74% in frontoparietal cortical 5-HT content at 1 and 3 weeks after injection. These changes were associated with a significant decrease by about 30% in the total number of specific SS receptors in the frontoparietal cortex at both times studied without influencing the apparent affinity of the receptors. Together, these results suggest that a portion of the frontoparietal cortex SS receptors may be localized presynaptically on the serotonergic nerve terminals. The 5,7-DHT did not affect SS-like immunoreactivity (SSLI) levels suggesting that SS and 5-HT are not colocalized within the same neuronal elements in the rat frontoparietal cortex.

5,7-Dihydroxytryptamine↗

PubMed1993

The effect of diazepam and the benzodiazepine antagonist CGS 8216 on the somatostatinergic neuronal system.

The effects of the benzodiazepines and somatostatin (SS) on learning and memory are the opposite of each other. To investigate a possible relationship between these two components, the effects of the administration over time of diazepam and of a benzodiazepine antagonist, 2-phenylpyrazolo [3,4-c]-quinolin-3(5H)-one (CGS 8216), on the levels of somatostatin-like immunoreactivity (SSLI) and on the binding of [125I]Tyr11-somatostatin were studied in the hippocampus of the Wistar rat. Diazepam (5 mg/kg/day, i.p.) and CGS 8216 (20 mg/kg/day, i.p.) did not affect SSLI in the hippocampus, at the three times studied (3, 7 or 14 days). Administration of diazepam for 3 or 7 days decreased the number of somatostatin receptors in synaptosomes from the hippocampus, without influencing their apparent affinity. This decrease could be blocked by concomitant administration of CGS 8216, whereas CGS 8216 alone had no observable effect. After 2 weeks of daily injections of diazepam the levels of binding of somatostatin in the hippocampus returned to control values, coinciding with the tolerance that develops to chronically-administered benzodiazepine agonists. These results suggest that somatostatin receptors might be regulated by benzodiazepine receptors and perhaps may also play a role in some of the behavioural effects of the benzodiazepines.

Animals↗

PubMed1993

Effect of prenatal dopamine receptor blocking on somatostatin receptor binding in the developing rat brain.

To date, the possible functional interaction between the dopaminergic and the somatostatinergic system during the development of the brain is unknown. This study examines whether blockage of brain dopamine receptors during fetal life might influence postnatal somatostatin (SS) receptor development. Pregnant Sprague-Dawley rats were injected intraperitoneally with either haloperidol (2.5 mg/kg/day), which blocks dopaminergic receptors, or saline. The injections were given for 16 days, commencing on the 4th or 5th day after conception (as counted from the appearance of spermatozoa in daily vaginal smear). The administration of haloperidol during gestation did not affect the levels of somatostatin-like immunoreactivity (SLI) in the two brain areas at any of the times studied. However, this treatment resulted in a decrease in the total number of receptors for 125I-Tyr11-SS in frontoparietal cortex and hippocampal plasma membranes in the 14-day-old offspring but not at 21, 35, or 60 days after birth. No significant differences in the apparent SS binding affinity values were seen after fetal exposure to haloperidol. These results suggest that the development of SS receptors in rat frontoparietal cortex and hippocampus can be transitorily delayed by fetal blockage of dopamine receptors.

Animals↗

PubMed1992

Reduction of somatostatin receptors in rat hippocampus by treatment with 5,7-dihydroxytryptamine.

Several lines of evidence suggest that somatostatin (SS) may interact with serotonergic neurons in the central nervous system. To assess whether SS acts presynaptically on serotonin (5-hydroxytryptamine, (5-HT)) neurons, SS receptors were measured in membranes from the hippocampus, a brain region that receives dense serotonergic innervation and has a high number of SS receptors in control and 5,7-dihydroxytryptamine (5,7-DHT)-treated rats, at 1 and 3 weeks after injection. Intracerebroventricular (i.c.v.) injection of the 5-HT-specific neurotoxin 5,7-DHT (11 micrograms (free base) dissolved in 10 microliters of isotonic saline containing 0.01% ascorbic acid) produced a 70% reduction in hippocampal 5-HT content at 3 weeks after injection but not at 1 week. This change was associated with a significant decrease in SS receptor density in rat hippocampus only at 3 weeks following the injection, without influencing the apparent affinity of the receptors at any time. Administration of 5,7-DHT did not affect somatostatin-like immunoreactivity (SSLI) levels at both times studied. These results suggest that some of the hippocampal SS receptors may be localized presynaptically on the serotonergic nerve terminals.

5,7-Dihydroxytryptamine↗

PubMed1992

Desmethylimipramine pretreatment prevents 6-hydroxydopamine induced somatostatin receptor reduction in the rat hippocampus.

Several studies have shown anatomical and functional interconnections between catecholaminergic and somatostatinergic systems. To assess whether somatostatin (SS) may act presynaptically on catecholamine neurons, SS receptors were measured using radioligand test-tube binding assays on synaptosomes from hippocampus and frontoparietal cortex--areas that are innervated by catecholaminergic neurons with different densities and that have a high number of SS receptors--from control and 6-hydroxydopamine (6-OHDA)-treated rats. Intracerebroventricular (i.c.v.) injection of the catecholamine neurotoxin 6-OHDA (0.78 mg free base/kg of body weight in saline with 0.1% ascorbic acid) lowered hippocampal and frontoparietal cortical noradrenaline (NA) and dopamine (DA) levels at 1 week following the injection. Pretreatment of rats with desmethylimipramine (DMI) (40 mg/kg, intraperitoneal) prevented the drop in NA levels, but was not effective in attenuating DA depletion in the two brain areas studied. Treatment with 6-OHDA lowered the number of 125I-Tyr11-SS receptors in the hippocampus (130 +/- 19 vs. 266 +/- 16 fmol/mg protein, P < 0.001), whereas in the frontoparietal cortex a non significant 20% reduction in receptor number was found. The dissociation constants of 125I-Tyr11-SS binding to synaptosomes from frontoparietal cortex (0.65 +/- 0.06 vs. 0.60 +/- 0.04, P not significant) and hippocampus (0.44 +/- 0.04 vs. 0.63 +/- 0.14, P not significant) were similar in control and treated groups. Pretreatment with DMI reversed up to 80% of the effect of 6-OHDA on hippocampus SS receptors. DMI alone had no observable effect on the number and affinity of SS receptors. The 6-OHDA and the DMI treatment did not affect SLI levels in the brain areas studied. These results suggest that a portion of the hippocampal SS receptors may be localized presynaptically on the noradrenergic and dopaminergic nerve terminals.

Animals↗

PubMed1992

Somatostatin receptors increase in the olfactory bulb of developing pups after perinatal exposure to cocaine.

The effects of chronic prenatal and/or postnatal exposure to cocaine on somatostatin concentration and receptors were studied in the olfactory bulbs of rat pups at birth and at 15 days old. Wistar rats were injected subcutaneously with single daily doses of 40 mg cocaine hydrochloride/kg from days 7 to 19 of gestation, from day 7 of gestation to day 15 postpartum or from parturation to day 15 postpartum. Fetal exposure to cocaine decreased SS concentrations in the olfactory bulb of the newborn pups while prenatal-plus-postnatal exposure increased this parameter. Administration of cocaine only during lactation did not induce any change. Exposure during gestation or during nursing induced an increase in the total number of somatostatin receptors and a decrease in the affinity constant in the olfactory bulb of newborn and 15-day-old pups. These results suggest that the development of somatostatin receptors in the olfactory bulb can be altered by prenatal and/or nursing period exposure to cocaine.

Animals↗

PubMed1992

Vasoactive intestinal peptide receptors in rat liver after partial hepatectomy.

We describe the status of vasoactive intestinal peptide (VIP) receptors in regenerating liver. VIP-stimulated adenylate cyclase activity was markedly decreased in proliferating liver 3 days after partial (70%) hepatectomy. This was associated with a reduced efficacy of VIP (53% compared with controls), with no change in the potency of the peptide (ED50 0.8 nM). In contrast, forskolin- and guanosine 5'-[beta gamma-imido]triphosphate (Gpp[NH]p)-stimulated enzyme activities were not decreased after hepatectomy. The expression of Gs protein subunits (alpha and beta) was studied by cholera toxin-catalysed ADP ribosylation of alpha s and by immunoblotting of alpha s and beta subunits. Both subunits were increased in regenerating liver, further suggesting that the decreased response to VIP was not related to a decreased expression of Gs proteins. In fact, the reduced adenylate cyclase response to VIP in regenerating liver was associated with quantitative and structural changes in VIP receptors. Equilibrium binding data obtained with 125I-VIP indicated the presence of two classes of binding sites, the Kds of which were not altered after hepatectomy. In contrast, changes in binding capacity (Bmax.) were as follows: 0.11 +/- 0.01 and 0.05 +/- 0.01 pmol/mg of protein for high-affinity sites in control and hepatectomized rats respectively; and 2.3 +/- 0.2 and 0.65 +/- 0.03 pmol/mg of protein for low-affinity sites in control and hepatectomized rats respectively. Moreover, affinity labelling experiments showed that the M(r) value of 125I-VIP-receptor complexes was higher in regenerating liver than in quiescent hepatocytes, e.g. 58,000 and 53,000 respectively. It is concluded that VIP receptors are altered in regenerating liver, resulting in a decreased response of adenylate cyclase to the neuropeptide.

Adenosine Diphosphate Ribose↗

PubMed1992

Different response of astrocytes and Bergmann glial cells to portacaval shunt: an immunohistochemical study in the rat cerebellum.

The present study was performed in order to follow the response of rat cerebellum astroglial cells (Bergmann glial cells and astrocytes) to long-term portacaval shunt (PCS), by means of glial fibrillary acidic protein (GFAP) and vimentin immunoreactivities. Bergmann glia accumulated GFAP in response to PCS, whereas astrocytes decreased GFAP immunoreactivity when compared to control rats. The increase of GFAP occurs in cells located in the cerebellar layer where glutamate is mainly released. Since the vimentin content remained unaltered in response to PCS, when compared to control rats, it can be concluded that only the GFAP filaments are affected by PCS. Nevertheless, GFAP immunoreactivity presents regional differences in the cerebellar astroglial population, and the factors responsible for these variations are still unknown.

Animals↗