Effect of ligation of common bile duct on somatostatin levels and binding in cytosol of rabbit duodenal mucosa

Rabbits with ligation of the common bile duct, of one and three weeks duration, showed a significant increase of somatostatin content in duodenal mucosa and plasma as compared with control animals. The increase of mucosal somatostatin was associated with a decrease in the binding capacity of both high- and low-affinity binding sites without changes in the affinity values in cytosol of duodenal mucosa. These findings suggest that the number of somatostatin binding sites is inversely related to local levels of the peptide and support the hypothesis of somatostatin regulating its own binding sites.To whom correspondence should be addressed.     

Effects of alloxan-induced diabetes on somatostatin binding to cytosolic components of rabbit gastric fundic mucosa

Diabetes was induced by administration of alloxan (150 mg/Kg) to 24 h-fasted rabbits. Somatostatinlike immunoreactivity (SLI) and cytosolic binding sites for somatostatin in gastric fundic mucosa were studied using radiolabelled Tyr¹¹-somatostatin. Three months after the onset of the disease, the specific binding of somatostatin to these sites was seen to be significantly lower, due to a reduction in the number (but not the affinity) of specific somatostatin binding sites of high-affinity and a disappearance of the specific, somatostatin binding sites of low-affinity. These changes were associated with an increase in the SLI concentration in both gastric fundic mucosa and plasma.     

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.     

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.     

Somatostatin binding sites in cytosolic fractions of parietal and non-parietal cells from rabbit fundic mucosa

Specific binding sites for somatostatin have been found in the cytosolic fractions of both parietal and non-parietal cells from rabbit gastric fundic mucosa. The stoichiometric data suggested the presence of two classes of binding sites in both types of ceils. The number of low-affinity binding sites was significantly higher in parietal cells than in non-parietal cells. The reverse was true for the high-affinity binding sites. However, the affinity of each class of binding sites was similar in the cytosolic fractions of both parietal and non-parietal ceils. It thus appears that low-affinity somatostatin binding sites are mainly located in the parietal ceils whereas the high-affinity sites occur principally in the non-parietal cells.     

Effect of small intestinal resection on somatostatin binding to cytosol of rabbit gastric mucosa

Small bowel resection in the rabbit increased gastric (fundus and antrum) somatostatin content and decreased the number of somatostatin binding sites (but not their corresponding affinity values) in gastric (fundus and antrum) cytosol three weeks after surgery. Five weeks after resection the number of somatostatin binding sites at both fundic and antral levels as well as antral somatostatin content returned towards control values whereas the fundic concentration of the peptide remained increased. Present results together with the known inhibitory role of somatostatin on various gastric functions suggest that the gastric alterations showed by animals subjected to small bowel resection may be due, at least in part, to the observed decrease of the number of gastric somatostatin binding sites.     

Ultrastructural identification of round-granule EC cells in rabbit fundic mucosa

In endocrine (EC) cells of rabbit fundic mucosa, it is practically impossible to obtain unequivocal ultrastructural identification of all cells found in order to perform morphometric analysis. In addition to classic EC cells with pleomorphic granules, a cell type with entirely round granules is encountered which can be confused with non-EC cells. To solve this problem, all EC cells in our study were first identified by their 5-HT (immunocytochemistry) and argentaffinity. Examination of the fine structures of reactive cells then revealed that the round granules of EC cells were differentiated from those of non-EC cells by the existence of a dense core surrounded by a less dense halo, a feature providing unequivocal ultrastructural identification. EC cells with round granules showed less argentaffinity and less immunoreactivity to 5-HT as compared with classic EC cells. After labelling with [3H]L-dopa, EC cells with round-granules displayed an overall staining index higher than that of classic EC cells and comparable with that of D cells; however, the nuclear staining index was higher than that of D cells.     

Upregulation of serum retinol in experimental acute renal failure

Serum vitamin A homeostasis was studied in rats with nonfiltering kidneys prepared by ligation of renal arteries. Within 1-2 h of acute renal failure, the serum retinol level increased by 11-73% and was maintained for at least 4 h. More than 90% of the increase in serum retinol was associated with retinol in the retinol binding protein-transthyretin (RBP-TTR) complex. The activities of acyl-CoA:retinol acyltransferase and retinyl-palmitate hydrolase were not altered by short-term acute renal failure. Oral administration of 3H-labeled retinol 3 h before surgery resulted in 350% more tritium in the serum retinol-RBP-TTR complex of rats with acute renal failure as compared to sham-operated rats; this increase represented the fraction of retinol in RBP-TTR contributed by hepatic retinol from newly absorbed 3H-labeled retinol. Total retinol in the retinol-RBP-TTR complex was increased by only 60%. We conclude that short-term acute renal failure causes rapid upregulation of serum retinol-RBP-TTR; the extent of the increase depends on the magnitude of hepatic vitamin A stores, particularly the retinol pools. We hypothesize that kidney modulates the regulation of hepatic release of retinol-RBP from the pool of newly acquired retinol.     

Lipid peroxidation--an initial event in experimental acute renal failure

A method was developed to monitor the occurrence of lipid peroxidation (LPO) during ischemia and Na-maleate-induced acute renal failure (ARF) on male rats in vivo by measuring malondialdehyde (MDA) levels in arterial and renal venous blood and in urine. No signs of LPO could be detected under control conditions. In ischemic ARF produced by 45 min of renal artery clamping a steep increase of MDA was found in the renal venous effluent immediately after starting reperfusion. This effect was nearly abolished after 5 min of blood reflow while glomerular filtration remained at 5% of control value during a 90-min postischemic observation period. Intoxication with Na-maleate leads to enhanced LPO in combination with an impaired renal function 2 h after administration. These findings would well explain cellular damage and some aspects of renal dysfunction associated with the initiation phase of ARF.     

Age dependence of somatostatin levels and somatostatin binding in the rat brain

1. Somatostatin-like immunoreactivity (SLI) and 125I-Tyrl-somatostatin binding were measured from the brains of rats aged 1, 8 and 18 months. 2. Somatostatin binding was reduced in the striatum, frontal cortex, hypothalamus and hippocampus of the 8-month-old rats compared to the 1-month-old group. 3. Somatostatin binding was reduced in the striatum, frontal cortex and hippocampus of the 18-month-old rats compared to the 1-month-old group. 4. The reduction (40%) was most striking in the frontal cortex. 5. In no area of the brain did changes in SLI differ significantly between the different age groups.     

Evidence for somatostatin binding sites in rabbit kidney

Specific binding sites for somatostatin have been identified in cytosolic fraction of rabbit kidney (cortex and outer medulla) using 125I-Tyr11-somatostatin. The binding was saturable and reversible, as well as time and temperature dependent. Optimal pH for binding was observed at about 7.4. Scatchard plots were compatible with the existence of two classes of binding sites: a first class with a high affinity (Kd = 40 nM) and a low binding capacity (2.0 pmol somatostatin/mg protein) and a second class with a low affinity (Kd = 222 nM) and a high binding capacity (114.3 pmol somatostatin/mg protein). Vasoactive intestinal peptide, neurotensin, substance P, Leu-enkephalin and vasopressin had practically no effect on somatostatin binding. The properties of these binding sites strongly support the concept that somatostatin could behave as a regulatory peptide on the rabbit kidney.     

Species variations of somatostatin concentrations and binding sites in jejunal mucosa

1. Somatostatin-like immunoreactivity (SLI) and specific binding of 125I-Tyr11-somatostatin were measured in jejunal mucosa of the mouse, rat, hamster, rabbit and guinea-pig. 2. The SLI concentrations in guinea-pig and rabbit were much greater than those in other rodents considered. 3. Somatostatin binding varied greatly with the species examined, the highest values being observed in cytosolic fraction of guinea-pig and rabbit jejunal mucosa, but the lowest ones in mouse. 4. The observed differences in somatostatin binding were not related to varying extents of degradation by the diverse cytosolic preparations studied. 5. The binding sites were highly specific for somatostatin in all rodent species studied. 6. There appears to be a direct relationship between somatostatin levels and somatostatin binding sites in jejunal mucosa when considering a variety of rodent species usually employed as laboratory animals.     

Alleviation of experimental acute renal failure in rats by reduction of renal mass

An acute renal failure (ARF) has been produced by glycerol injection on rats unilaterally nephrectomized 48 h before. Rats with reduced renal mass showed polyuria and significantly lower azotemia than controls with ARF. This data might be explained by increased glomerular plasma flow in the remnant kidney previous to ARF induction.     

Studies on the mechanism of non-oliguric experimental acute renal failure.

Although acute renal failure, caused either by renal ischemia or nephrotoxic agents, is usually characterized by oliguria, a severe fall in glomerular filtration rate, and a fall in renal blood flow, some patients and experimental models display a non-oliguric pattern of renal injury. The present study was designed to evaluate the mechanism of preservation of high urinary flow rate under this condition. Following the administration of the aminoglycoside gentamicin to rats for five days, a decrease in concentrating ability was demonstrated, caused by impaired vasopressin-mediated water transport. Further treatment resulted in a fall in Cin to 15 percent of control, although RBF was reduced to only 67 percent of control, and urine flow rate rose above control levels. Induction of acute and renal failure with dichromate was associated with variable high or low urinary flow rates according to pre-injury intake of sodium. Urine volume correlated directly with cortical blood flow. These data suggest that the non-oliguric pattern of acute renal injury is caused by preservation of cortical perfusion in the setting of severe tubular injury.     

Renal proton magnetic resonance in experimental acute renal failure in rats

Cortical, medullary and papillary T1 and T2 water proton relaxation times were measured at 37 degrees C, 20 MHz. The measurements were made using kidneys from rats affected by many forms of experimental acute renal failure (ARF), namely acute hemorrhagic hypovolemia, angiotensin II administration, antidiuretic hormone (ADH) administration, glycerol, and other nephrotoxins (gentamicin, cisplatinum, cyclosporine), renal artery occlusion for different periods of time, and ureteral ligation. From the T1 and PW (percent tissue water content) the bound water (FB) and HF (percent water bound/g solid) were calculated according to a fast proton diffusion model. In most experimental models studied, the experiments were repeated following paramagnetic enhancement with GdDTPA administration (70 mmol/kg BW). By profiling the deviations from normal, it was possible to differentiate the ischemic (shortened T1, prolonged T2), obstructive (very high T1 and T2 in both cortex and medulla) and nephrotoxic (prolonged T2) forms of ARF. Significant changes in free/bound water compartments occurred, though their biological significance is unknown. T1 and T2 ratios before and after paramagnetic enhancement correlated well with estimates of glomerular filtration rate. In the first minutes following acute hemorrhagic hypovolemia, the intrarenal water distribution remained unchanged. After GdDTPA significant water proton T1 and T2 changes characterized the immediate posthemorrhagic state similar to the effect of ADH.     

Histochemical study of rabbit duodenal mucosa carried out using lectins

The Authors report histochemical findings about rabbit's duodenal mucosa. The present study has been carried out using five different lectins (Peanut Agglutinin (PNA), Dolichos Biflorus Agglutinin (DBA), Wheat Germ Agglutinin (WGA), Soybean Agglutinin (SBA), Ulex Europaeus Agglutinin I (UEA-I). These lectins have been labelled with Horseradish Peroxidase and binding sites have been stained with 3-3' Diaminobenzidine, according to Farragiana et al. The PNA reacted with the glandular cells, while the reaction was negative in the superficial cells. The DBA reacted exclusively with the glandular cells. The superficial and the glandular cells showed strong positive binding sites to the WGA and slight positive binding sites to the SBA. The UEA-I did not react with the epithelial cells. The presence of binding sites for the lectins we have used in the present study, shows a different glycoprotein composition of the cellular secretion, in comparison with the other animals we have already studied. In addition, these lectins can not be used as cellular differentiation markers in the epithelial cells of the rabbit's duodenal mucosa.     

Influence of experimental diets on cholesterol and triglyceride levels of rabbit blood serum lipoproteins

Groups of rabbits were fed for six weeks various diets: standard died + ethanol, high-cholesterol diet and a high-cholesterol + ethanol one. During the next six weeks every diet was supplemented with a fresh vegetable (carrot). Cholesterol and triglycerides were determined in the whole serum and in lipoprotein fractions. In rabbits fed standard diet ethanol caused a moderate elevation of VLDL cholesterol and triglyceride and LDL cholesterol levels. In animals on high-cholesterol diet cholesterol and triglyceride concentrations in these fractions were very high. Simultaneous consumption of large amounts of cholesterol and of ethanol resulted in a greater rise of cholesterol concentration in the whole serum and in VLDL and LDL fraction than did high-cholesterol diet alone. Addition of carrot caused a pronounced reduction of serum cholesterol concentration in animals fed all kinds of diets. The reduction concerned mainly VLDL.     

Influence of triamcinolone and somatostatin on morphometric parameters of cultured intestinal mucosa

Summary Mucosal biopsies from rabbit ileum were organ cultured for 24 h. The influence of triamcinolone and somatostatin on vilus height and diameter as well as crypt depth and the number of mitoses was measured at various times during 24 h of culture as indices of cell proliferation and tissue maintenance. It could be shown that triamcinolone reduced cell proliferation slightly but preserved mucosal structure in organ culture. Somatostatin inhibited crypt cell proliferation, without any effect on other morphological parameters.