Biomedical subjects

E Arilla

Publications and source records attributed to E Arilla.

124 records · Page 7Linked to original sources

PubMed1985

Somatostatin binding sites in cytosolic fraction isolated from rabbit antral and fundic gastric mucosa.

Specific binding sites for somatostatin have been identified and characterized in cytosolic fraction of rabbit gastric mucosa at both antrum and fundus levels. The binding depended on time, temperature and pH, and was reversible and saturable. The stoichiometric data suggested the presence of two classes of binding sites: a class with high affinity (Kd = 26.7 and 37.0 nM in antrum and fundus, respectively) and low capacity (2.1 and 4.1 pmol somatostatin/mg protein in antrum and fundus, respectively), and a class with low affinity (Kd = 246.4 and 162.5 nM in antrum and fundus, respectively) and high capacity (134.1 and 110.9 pmol somatostatin/mg protein in antrum and fundus, respectively) at 25 degrees C and pH 7.4. The binding sites were shown to be highly specific for somatostatin since neuropeptides such as Leu-enkephalin, neurotensin and substance P behaved as ligands with very low affinity.

Animals↗

PubMed1985

Somatostatin binding sites in cytosolic fraction of rabbit intestinal mucosa: distribution throughout the intestinal tract.

Specific binding sites for somatostatin have been identified in cytosolic fraction of both small and large intestinal mucosa. The stoichiometric data suggested the presence of two classes of binding sites in each part of the intestine. The binding capacity varied depending on the segment considered (rectum greater than duodenum = jejunum greater than ileum, caecum and colon). However, the affinities of the binding sites were similar throughout the whole intestinal mucosa, with the exception of rectum which showed higher Kd values. The binding sites were shown to be highly specific for somatostatin since neuropeptides such as vasoactive intestinal peptide, neurotensin, substance P and Leu-enkephalin did not show any effect upon somatostatin binding.

Animals↗

PubMed1985

Influence of ligation of pancreatic and bile ducts on the interaction of vasoactive intestinal peptide with rat duodenal epithelial cells.

The specific binding of vasoactive intestinal peptide (VIP) and the stimulatory effect of the neuropeptide on cyclic AMP in duodenal epithelial cells were modified 3 days following pancreaticobiliary exclusion. The binding capacity, but not the affinity, of VIP receptors decreased (by about 50%) as a consequence of the surgical manipulation. VIP was equally potent but showed a lower efficiency (about 45%) in stimulating cyclic AMP after ligation of the pancreatic and bile ducts. These observations may be either a consequence or a cause of the adaptive response of duodenal epithelium, the last possibility suggesting a role of VIP in the mechanisms of growth and differentiation of intestinal mucosa.

Animals↗

PubMed1985

Effect of resection of small intestine on the interaction of vasoactive intestinal peptide with rat colonic epithelial cells.

Vasoactive intestinal peptide (VIP) receptors and VIP-dependent cyclic AMP production were studied in rat colonic epithelial cells 3 days after a 60% resection of the small intestine. Basal cyclic AMP levels were similar in both control and resected animals. The potency, but not the efficiency, of the peptide on the stimulation of cyclic AMP production was diminished in cells from resected rats. Accordingly, the affinity of VIP receptors, but not the binding capacity, decreased as a consequence of the loss of a part of the small intestinal mucosa. These observations are consistent with the known inhibitory role of cyclic AMP on cell proliferation in colonic epithelium and other tissues and suggest a participation of VIP acting through the cyclic nucleotide in the compensatory hyperproliferative response of the colon following massive resection of the small intestine.

Animals↗

PubMed1984

Characterization of somatostatin binding sites in cytosolic fraction of rat intestinal mucosa.

Specific binding sites for somatostatin have been characterized in cytosolic fraction of rat intestinal mucosa by using 125I-labelled Tyr11-somatostatin and a variety of physicochemical conditions. The binding depended on time, temperature and pH, and was reversible, saturable and specific. At apparent equilibrium, the specific binding of 125I-Tyr11-somatostatin was competitively inhibited by native somatostatin in the 1 nM-4 microM concentration range. Binding studies suggested the presence of two classes of binding sites: a class with high affinity (Kd = 0.07 microM) and low capacity (4.6 pmol/mg protein) and a class with low affinity (Kd = 1.05 microM) and high capacity (277 pmol/mg protein) at 25 degrees C. Somatostatin exhibited competitive inhibition of tracer binding, while neuropeptides such as neurotensin, substance P, Leu-enkephalin, and vasoactive intestinal peptide were ineffective. The presence of somatostatin binding sites in cytosolic fraction of intestinal mucosa, together with the known occurrence of somatostatin in D-cells and nerve endings in the small intestine, strongly suggest that this peptide may be involved in the physiology and physiopathology of intestinal epithelium.

Animals↗

PubMed1984

Effect of 2-bromostearate on glucose-phosphorylating activities and the dynamics of insulin secretion in islets of Langerhans during fasting.

Glucose-phosphorylating activity and insulin secretion were measured in homogenates of isolated rat islets and of perfused rat pancreas, respectively. Fasting for 96 h produced a significant decrease of both low-and high-Km glucose-phosphorylating activities and blocked the insulin secretory response to glucose. In the presence of glucose, 0.25 mM 2-bromostearate, a known inhibitor of fatty acid oxidation, partially restored the insulin response to glucose that was lost during fasting. This effect paralleled the restoration of glucose-phosphorylation activities (primarily the high-Km component) seen when islets isolated from 96-h-fasted rats were preincubated with 0.25 mM 2-bromostearate. It is concluded that fasting-induced adaptations of glucose-phosphorylating enzymes could account, at least in part, for the reduced insulin secretory response to glucose. 2-Bromostearate, an inhibitor of fatty acid oxidation, is able to restore both insulin secretory response and glucose-phosphorylating activities, suggesting possible interrelations among the correlated impairment in insulin secretion, islet glucose-phosphorylating activity, islet glucose metabolism, and the oxidation of fatty acids in the B-cell during fasting.

Animals↗

PubMed1982

Extracellular calcium and glucose-induced insulin release during fasting in isolated perfused rat pancreas.

The effects of different concentrations of Ca2+ (2.5 or 7.5 mM) upon the kinetic and dynamic aspects of glucose-induced insulin release were investigated in the isolated perfused pancreas of fed and 4-day fasted rats. The curve relating the rate of insulin release to the glucose concentrations (2.75-33.4 mM) showed a sigmoidal shape and was similar at both Ca2+ concentrations in the fed state. Pancreas of fasted animals showed a diminished insulin secretion and the kinetic pattern was linear throughout the whole range of glucose concentrations studied at 2.5 mM Ca2+. Perfusion of pancreas from fasted rats with glucose at 7.5 mM Ca2+ resulted in an increase of insulin secretion but the kinetic behaviour continued to be linear. In contrast, pancreas of 4-day fasted plus 2-day refed rats showed a kinetic of glucose-induced insulin secretion with the cooperative mechanisms observed in fed control animals. It is concluded that changes in Ca2+ utilization by the pancreatic beta cell play little role in the decreased insulin release observed in the fasted state.

Animals↗

PubMed1981

Somatostatin action on insulin secretion induced by chicken and porcine vasoactive intestinal peptide in the perfused rat pancreas.

The isolated perfused rat pancreas with duodenal exclusion was used to study the stimulation of glucose-induced insulin release in response to chicken and porcine vasoactive intestinal peptide (VIP). The insulin response to 5.5 or 16.7 mM glucose was markedly enhanced by 750 pM porcine VIP and a concentration of 250 pM was still effective. At 250 pM, chicken VIp exhibited a slightly higher potency than porcine VIP at both glucose concentrations. The main difference between the two peptides was that the effect of porcine VIP disappeared immediately after the peptide suppression but tha of chicken VIP persisted for an additional period of 8-10 min. Somatostatin (10 ng/ml) blocked the stimulatory effect of both VIP molecules on glucose-induced insulin secretion. After suppression of VIP and somatostatin from the perfusion medium, insulin release increased to levels higher than those with glucose alone in the case of the avian peptide, but not in that porcine VIP. The data are consistent with previous results in the literature on stimulation of exocrine pancreas secretion and interaction with intestinal epithelium.

Animals↗

PubMed1980

Restoring effects of refeeding and dibutyril cyclic AMP on the increased glucagon secretion of rat pancreatic islets during starvation.

The glucagon release in the presence of glucose and the interaction of dibutyril cyclic AMP was studied in isolated pancreatic islets from fed and 96 h-fasted rats incubated for 30 min. In both states the increase of glucose concentration produced a similar inhibition of glucagon release and stimulation of cyclic AMP content. Higher glucagon secretion and lower cyclic AMP contents were observed in islets from fasted than in those from fed animals at both 2.75 and 16.7 mM glucose. Islets from rats starved for 96 h and refed for 48 h with normal diet or oral 20% glucose showed glucagon release patterns similar to those of controls. Addition of 2 mM dibutyril cyclic AMP to the incubation medium inhibited the fasting-induced increase of glucagon secretion at both glucose levels. These results show an inverse correlation between glucagon secretion and islet cyclic AMP content. However, the sensitivity of the islet to glucose-induced inhibition of glucagon secretion appears to be independent of the islet cyclic AMP levels.

Animals↗

PubMedDate not supplied

Cyclic hexa- and pentapeptide somatostatin analogues with reduced gastric inhibitory activity.

The gastric inhibitory activity of cyclic hexa- and pentapeptide analogues of somatostatin was investigated in conscious cats with gastric fistulae. Gastric acid and pepsin secretions were stimulated by pentagastrin. Cyclo(Phe-Phe-D-Trp-Lys-Thr-Phe) showed no inhibition of acid secretion at molar doses up to 50-times the ID50 for somatostatin. This peptide inhibited pepsin secretion at the highest dose (50 micrograms kg-1 hr-1), and its potency is approximately 0.005 compared with somatostatin (1.0). Cyclo(Pro-Phe-D-Trp-Lys-Thr-Phe) inhibited acid (approximately 50%) and pepsin (approximately 85%) secretions, but the inhibition was not dose-related being similar with doses of 10 to 50 micrograms kg-1 hr-1. The cyclic pentapeptide, cyclo(7-aminoheptanoyl-Phe-D-Trp-Lys-Thr), was inactive in the dose range studied, with a potency less than 0.01. Cyclo[7-aminoheptanoyl-Phe-D-Trp-Lys-Thr(Bzl)] has been described as a somatostatin antagonist with respect to inhibition of growth hormone, insulin and glucagon release in rats [2]. Up to 60-fold molar excesses of this peptide failed to antagonise the inhibitory activity of somatostatin in the stomach. The results demonstrate that residues outside the central 6-11 region of somatostatin are very important for its gastric activity. The lack of gastric antagonistic activity of the pentapeptide antagonist indicates that these residues are likely to be involved in receptor recognition/binding.

Animals↗

PubMedDate not supplied

Interaction of somatostatin with isolated cytosol from rabbit renal papilla.

Specific binding sites for somatostatin have been characterized in cytosolic fraction of rabbit renal papilla. The interaction of 125I-Tyr11-somatostatin with cytosolic fraction was rapid, reversible, specific, saturable and dependent on temperature. At 25 degrees C the binding data were compatible with the existence of two classes of binding sites: a high-affinity class with a Kd = 57.7 nM and a low-affinity class with a Kd = 217.4 nM. Somatostatin binding sites exhibited a high degree of specificity since neuropeptides such as Leu-enkephalin, neurotensin, substance P, vasopressin and vasoactive intestinal peptide behaved as ligands with null or very low affinity.

Animals↗

PubMedDate not supplied

Postnatal development of somatostatin levels and its binding sites in rabbit gastric mucosa.

Using a specific radioimmunoassay technique, we have determined somatostatin-like immunoreactivity (SLI) in acid extracts of gastric (fundic and antral) mucosa as well as the specific binding of 125I-Tyr11-somatostatin to cytosol of the stomach of 0 to 150 days postnatal rabbits. The levels of somatostatin in both fundus and antrum decreased from birth up to day 5 followed by a sharp increase from 5 to 10 days, then decreased progressively until day 35. After this age, the somatostatin concentration remained relatively stable. The number of specific somatostatin binding sites of both high- and low-affinity increased gradually (without changes in the affinity values) with the development of rabbits, reaching the adult level by 35 days. However, there was an apparent lack of high-affinity sites immediately after birth (day 0). The somatostatin binding sites had characteristics identical with those found in adult animals with regard to their respective specific ligands.

Age Factors↗

PubMedDate not supplied

Somatostatin binding to dissociated cells from rat cerebral cortex.

A method has been developed for the study of somatostatin (SS) binding to dissociated cells from rat cerebral cortex. Binding of [125I] [Tyr11]SS to cells obtained by mechanical dissociation of rat cerebral cortex was dependent on time and temperature, saturable, reversible and highly specific. Under conditions of equilibrium, i.e., 60 min at 25 degrees C, native SS inhibited tracer binding in a dose-dependent manner. The Scatchard analysis of binding data was linear and yielded a dissociation constant of 0.60 +/- 0.08 nM with a maximal binding capacity of 160 +/- 16 fmol/mg protein. The binding of [125I] [Tyr11]SS was specific as shown in experiments on tracer displacement by the native peptides, SS analogues, and unrelated peptides.

Animals↗

PubMedDate not supplied

Effect of prenatal and postnatal cocaine exposure on somatostatin content and binding in frontoparietal cortex and hippocampus of developing rat pups.

The effects of cocaine administration to pregnant and/or nursing rats on somatostatin (SS) concentration and receptors in offspring brains at birth and 15 days of age were studied. SS was measured by radioimmunoassay and SS receptors by radio receptor assay in frontoparietal cortex and hippocampus. In newborn and 15-day-old animals the exposure to cocaine produced an increase in SS concentration in the frontoparietal cortex and a decrease of this parameter in the hippocampus. Administration of cocaine only during lactation did not induce such changes. Exposure during pregnancy or nursing induced in 0- or 15-day-old offspring an increase in the total number of SS receptors and a decrease in the affinity constant only in the cortex.

Aging↗

PubMedDate not supplied

Effect of ammonium acetate on the somatostatinergic system in the rat frontoparietal cortex.

Short (90 min)-, mid (5 days)-, and long-term (15 days) ammonium acetate (5 mmol/kg IP) administration decreased the number of specific [125I][Tyr11]somatostatin receptors in synaptosomes from the frontoparietal cortex without changing the affinity constant. Administration of ammonium acetate did no affect the levels of somatostatin-like immunoreactivity in the frontoparietal cortex. The administration of a single dose of N-carbamyl-L-glutamate (1 mmol/kg) plus L-arginine (1 mmol/kg) 1 h before the last administration of ammonium acetate totally blocked the inhibitory effects of the latter on somatostatin receptor number in the frontoparietal cortex synaptosomes. N-Carbamyl-L-glutamate plus L-arginine alone had no observable effect on the somatostatinergic system. The decrease in the number of somatostatin receptors induced by ammonium acetate might reflect decreased target cell sensitivity to somatostatin, a phenomenon that could contribute to the depressed neuronal excitability induced by ammonia in the rat frontoparietal cortex.

Acetates↗

PubMedDate not supplied

Modification of somatostatin content and binding in jejunum from celiac children.

The concentration of somatostatin was studied in controls as well as in plasma and jejunal mucosa from celiac children with and without jejunal villous atrophy. The binding of somatostatin to cytosolic fraction, isolated from jejunal mucosa from celiac patients and controls, was also investigated. Fasting plasma somatostatin concentrations were not significantly different among the various groups studied. However, the jejunal somatostatin content was significantly higher in the group of celiac children with subtotal villous atrophy as compared to control group and celiac children with normal villous architecture. The binding of somatostatin to cytosol of jejunal mucosa was significantly decreased in the group of celiac children with subtotal villous atrophy. The present results suggest that somatostatin may be involved in the pathophysiological processes of celiac disease.

Binding Sites↗