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Biomedical subjects

E Blazquez

Publications and source records attributed to E Blazquez.

At least 19 recordsLinked to original sources
PubMed1998

Glucagon-like peptide-1-(7-36)amide increases pulmonary surfactant secretion through a cyclic adenosine 3',5'-monophosphate-dependent protein kinase mechanism in rat type II pneumocytes.

Glucagon-like peptide-1 (GLP-1) receptor messenger RNA has been identified in cells considered type II pneumocytes that are involved in the synthesis and secretion of the pulmonary surfactant. In an attempt to open new insights into the control of surfactant secretion, we studied the effects of glucagon-related peptides in this process. Accordingly, type II pneumocytes were isolated from Wistar rat lungs and cultured overnight with [methyl-14C]choline, and then the basal and stimulated secretions of [14C]phosphatidylcholine were measured. GLP-1(7-36)amide stimulated phosphatidylcholine secretion in a concentration-dependent manner in the 1-100 nM range; the concentration of the peptide that produced a half-maximal response was 10 nM. Exendin-4 induced similar effects. No changes were observed when GLP-1-(1-37), GLP-2, or exendin-(9-39) was added to the medium. However, the latter reversed the stimulatory effects of GLP-1-(7-36)amide and exendin-4. A study of the mechanism through which GLP-1-(7-36)amide exerts its stimulatory effect was carried out using different agents that are well known stimulants of phosphatidylcholine secretion. GLP-1-(7-36)amide did not produce any change in the stimulatory effect observed with terbutaline or 8-bromo-cAMP, suggesting the involvement of a cAMP-dependent protein kinase in the stimulatory effect of this peptide on phosphatidylcholine secretion. It was further supported by the use of inhibitors of protein kinases and by the stimulation of cAMP production in type II pneumocytes incubated with either GLP-1-(7-36)amide or exendin-4.

Adrenergic beta-Agonists↗
PubMed1996

Levels of lipoprotein(a) and plasma lipids in Spanish children aged from 4 to 18 years.

Increased plasma lipoprotein(a)-Lp(a)-levels are linked to a high risk of cardiovascular disease unrelated to other lipoproteins. It seems that Lp(a) values in childhood remain unaltered up to adulthood. In a randomly chosen population of 1970 children, aged from 4 to 18 years and living in a Spanish community, the following serum parameters were studied: total cholesterol, total triglycerides, Lp(a), high-density lipoprotein cholesterol and low-density lipoprotein cholesterol. Mean Lp(a) serum values were 15.0 +/- 14.7 mg dl-1. No differences were seen between either sex in the first years of childhood. Of the studied children, 15.1% presented Lp(a) concentrations above 30 mg dl-1. A correlation between Lp(a) and total cholesterol concentrations, which disappeared when low-density lipoprotein cholesterol concentrations were corrected according to cholesterol present in Lp(a), was observed.

Adolescent↗
PubMed1996

Effect of dietary fat saturation on LDL oxidation and monocyte adhesion to human endothelial cells in vitro.

Forty-two healthy men and women were subjected to four consecutive dietary periods differing in the fat content of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (n-6) [PUFA(n-6)] and (n-3) [PUFA(n-3)]. Plasma lipids, vitamin E, and in vitro LDL oxidation were examined during each period. Adhesion of human monocytes to cultured human endothelial cells was used as a functional test to identify differences in the biological properties of LDL from each dietary period. Consumption of an SFA-rich diet resulted in higher LDL cholesterol (4.06 +/- 0.85 mmol/L, P < .05) than did consumption of MUFA- (3.59 +/- 0.75 mmol/L), PUFA(n-6)- (3.44 +/- 0.77 mmol/L), or PUFA(n-3)- (3.31 +/- 0.8 mmol/L) rich diets. HDL cholesterol was lower during both PUFA-rich diets (1.24 +/- 0.28 and 1.27 +/- 0.28 mmol/L for n-6 and n-3, respectively) than during the SFA-(1.32 +/- 0.36 mmol/L) and MUFA- (1.32 +/- 0.34 mmol/L) rich diets. LDL resistance to copper-induced oxidation, expressed as lag time, was highest during the MUFA-rich diet (55.1 +/- 7.3 minutes) and lowest during the PUFA(n-3)- (45.3 +/- 7 minutes) and SFA- (45.3 +/- 6.4 minutes) rich diets. LDL induction of monocyte adhesion to endothelial cells was lower during the MUFA-rich diet than the other periods. The highest monocyte adhesion was obtained during the PUFA(n-3) and SFA dietary periods. In conclusion, an MUFA-rich diet benefits plasma lipid levels compared with an SFA-rich diet. Furthermore, this diet results in an increased resistance of LDL to oxidation and a lower rate of monocyte adhesion to endothelial cells than the other dietary fats examined.

Adult↗
PubMed1995

Glucagon-like peptide-1(7-36)amide induces the release of aspartic acid and glutamine by the ventromedial hypothalamus of the conscious rat.

Glucagon-like peptide-1(7-36)amide (GLP-1(7-36)amide) and its own receptor have been found in the hypothalamus and brain stem of the rat. In an attempt to gain further insight into the role of this peptide in brain functioning we investigated the effects of GLP-1 (7-36)amide on the release of excitatory amino acid neurotransmitters by the ventromedial hypothalamus using an experimental microdialysis approach. GLP-1(7-36)amide produced an immediate increase in the extracellular concentrations of aspartic acid and glutamine, p < 0.01 and p < 0.05, respectively. By contrast, extracellular concentrations of glutamic acid, alanine, threonine, and tyrosine were unaffected. The results of this study show a stimulatory effect of GLP-1(7-36)amide on the release of aspartic acid and glutamine by the ventromedial hypothalamus of the rat.

Animals↗
PubMed1993

Isolation of a glycosyl-phosphatidylinositol (GPI) from rat brain.

Brain lipids were labelled with [1-14C]-isethionyl acetimidate and purified by sequential thin layer chromatography. Four labelled peaks were obtained, the first ones migrating with the same Rf as glycosyl-phosphatidylinositol (GPI). Further proof of the isolation of GPI was obtained by the observations that 44.8% of the radioactivity associated with the lipid in peak I was converted to the water phase by the effect of a PI-specific phospholipase C, and that the soluble material so obtained produced a dose-dependent inhibition of cAMP-dependent protein kinase activity. These findings indicate a biological equivalence between GPI and its polar head group from rat brain and those described in other cell types, and are consistent with the proposed role of these molecules in cellular signalling.

Animals↗
PubMed1993

The effect of acarbose on the intestinal metabolism of glucose in vitro.

The effect of acarbose on the intestinal metabolism of glucose was investigated using an in vitro perfused preparation of the isolated rat small intestine-pancreas. In preparations perfused without intraluminal sucrose administration, the total glucose recovered in the portal effluent and the portal values of lactate, pyruvate and alanine did not depend on whether or not acarbose [1.5 mg/kg body weight (b.w.)] was present in the intestinal lumen. The intestinal glucose and lactate contents were very low at the end of the experiment, and identical with or without acarbose. Insulin and glucagon concentrations remained constant during the whole perfusion period. After intraluminal administration of sucrose a clear increase in portal glucose concentration was observed, which was severely reduced by acarbose administration no changes in portal levels of lactate, pyruvate, alanine, insulin and glucagon were observed. The intestinal content of sucrose at the end of the study was significantly higher in the presence of acarbose (1.5 mg/kg b.w.), while the glucose concentration was low both with and without acarbose (0.20 +/- 0.08 vs 0.29 +/- 0.09 mmol/l respectively). These results suggest that acarbose does not influence the metabolic utilization of the glucose being translocated from the lumen.

Acarbose↗
PubMed1992

Effect of dietary monounsaturated fatty acids on plasma lipoproteins and apolipoproteins in women.

To determine the effects of dietary fat saturation on plasma lipoproteins, we studied 21 free-living normolipidemic women (13 pre- and 8 postmenopausal) on three consecutive diet periods. During the first 4 wk they consumed a saturated diet rich in palm oil and butter [19% saturated fatty acids (S), 14% monounsaturated fatty acids (M), and 3.5% polyunsaturated fatty acids (P)], followed by 6 wk of a monounsaturated diet rich in olive oil (11% S, 22% M, and 3.6% P), and 6 wk of a polyunsaturated diet rich in sunflower oil (10.7% S, 12.5% M, and 12.8% P). Compared with the diet rich in saturated fatty acids, both diets rich in unsaturated fatty acids had similar lowering effects on total and low-density-lipoprotein cholesterol. High-density lipoprotein cholesterol and apolipoprotein A-I were higher in the monounsaturated-rich period than in the polyunsaturated-rich (10.5% and 12.7% respectively, P less than 0.001) and the saturated-rich period (5.3%, and 7.9%, respectively, P less than 0.05). These effects were independent of menopause status. Our data show that at this level of fat intake (36% as calories), a monounsaturated-rich diet results in a less atherogenic lipid profile than either polyunsaturated- or saturated-rich diets.

Adult↗
PubMed1985

Glucagon-like peptide-1 does not have a role in hepatic carbohydrate metabolism.

Glucagon-like peptide-1 does not have specific, high-affinity receptors on rat liver membranes, does not displace glucagon from glucagon receptors on these membranes and does not stimulate the production of cyclic AMP by isolated rat hepatocytes. In the presence of glucagon, high concentrations of glucagon-like peptide-1 do not significantly alter the production of cyclic AMP. Thus, glucagon-like peptide-1 appears unlikely to have a direct action on hepatic carbohydrate metabolism.

Animals↗
PubMed1984

Changes in adenylate cyclase and phosphodiesterase activities during the growth cycle of adult rat hepatocytes in primary culture.

Long-term primary adult rat hepatocyte cultures show growth-state-dependent changes in adenylate cyclase and cAMP phosphodiesterase activities. Cellular adenylate cyclase activity decreases to undetectable levels within 1 day postplating, reappears on Days 4-5, and becomes maximal on Day 9. Membrane adenylate cyclase and cellular cAMP formation are insensitive to glucagon during log phase (Days 4-8) but not during lag (Day 1) or stationary phase (Day 12). Cyclic AMP phosphodiesterase activities (soluble and particulate) fall approximately equal to 70% by Day 2 but recover as proliferation begins. By contrast, the particulate phosphodiesterase assayed at 100 microM cAMP, decreased during Days 0-2. These observations simulate changes seen during liver proliferative transitions in vivo and, therefore, further support the use of these cultures as a developmental model.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1984

Evidence of glucagon biosynthesis involving protein intermediates in rat salivary glands.

In an attempt to determine the ability of rat submaxillary glands to synthesise glucagon via protein intermediates, isolated cells from these glands were incubated in vitro with 3H-L-tryptophan and the acid-ethanol extracts of the cells were purified on Bio-Gel P-30 columns. Aliquots of the eluates were incubated with a C-terminal glucagon antiserum (30K) and the radioactivity bound to the glucagon antibody appeared to be distributed among proteins of Molecular weight greater than 40.14 and 3.5 Kdaltons. A similar elution pattern was obtained in the presence of urea (7 mol/l) and guanidine hydrochloride (6 mol/l). To determine the molecular weight of the immunoreactive material eluting before the 3.5 Kdalton polypeptide, aliquots of the cell extracts were immunoprecipitated and analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Polypeptides of 125.8, 63.1, 42.6 and 14.4 Kdaltons were obtained. These polypeptides incorporate more radioactive tryptophan with increase in the time of incubation. Pulse-chase experiments with unlabelled tryptophan, cycloheximide-treatment of isolated cells and limited tryptic digestion of the larger glucagon immunoreactive component, transform it into a 3.5 Kdalton polypeptide with immunological characteristics indistinguishable from pancreatic glucagon. These results suggest that the larger molecule contains glucagon and thus may serve as a precursor or an intermediate of extrapancreatic glucagon biosynthesis.

Animals↗
PubMed1982

Regulatory effect of glucagon on its own receptor concentrations and target-cell sensitivity in the rat.

To evaluate the role of glucagon on its hepatocyte receptor concentrations, groups of rats were injected with a long-acting glucagon preparation (20 [G-20], 40 [G-40] or 60 [G-60] micrograms/100 g body weight) every 8 h for 4 days. Glucagon receptors in liver plasma membranes of treated animals were decreased in number (control = 1.66 +/- 0.20 ng/0.5 mg protein versus G-20 = 1.24 +/- 0.26, G-40 = 1.03 +/- 0.26, G-60 = 0.70 +/- 0.03 ng/0.5 mg protein; p less than 0.05, less than 0.001, less than 0.001, respectively), but they were indistinguishable from receptors of control rats by other criteria including affinity and kinetics of association. Degradation of both glucagon and receptor sites did not account for differences observed in binding. Similar results were obtained with isolated hepatocytes. In relation to controls, isolated hepatocytes of treated rats had a reduced number of receptors (control = 0.70 +/- 0.05 versus G-40 = 0.47 +/- 0.04 ng/10(6) cells; p less than 0.02) proportionate to the decreased glucagon-stimulated production of cyclic AMP and glucose. Four to eight hours exposure of cultured hepatocytes of nontreated rats to 4 x 10(-8) mol/l glucagon produced a decreased binding of 125I-glucagon to its receptor (p less than 0.05). In contrast, hormone exposure for shorter periods of time (0-2 h) was without effect. These results suggest (1) an inverse relationship between circulating glucagon levels and hepatocyte glucagon receptor concentration, and (2) a direct relation between receptor number and target-cell response.

Animals↗
PubMed1977

Demonstration of gastric glucagon hypersecretion in insulin-deprived alloxan-diabetic dogs.

The contribution of the gastric fundus to the hyperglucagonemia of poorly controlled diabetes was studied in insulin-deprived alloxan-diabetic dogs by simultaneously measuring plasma glucagon in the venous effluents of the fundus and the pancreas, and the inferior vena cavae plasma. In the basal state, mean glucagon averaged 411 +/- 45 pg./ml. in the gastric vein and 941 +/-161 in the pancreaticoduodenal vein; both values were significantly above the vana caval level of 281 +/-35 (p less than 0.01). Intravenous arginine infusion to 1,180 +/- 432 after 1.5 minutes; this was significantly above the mean vena caval glucagon concentration which reached a peak of only 352 +/- 74 (p less than 0.01 to 0.05). Intragastric instillation of arginine was followed by a doubling of gastric vein glucagon within 10 minutes, and the increases in the gastric vein were significantly greater than in the peripheral plasms at several points. The infusion of insulin at a rate of 0.0015 u./kg./min. rapidly lowered glucagon in the gastric and pancreaticoduodenal veins, abolishing the gradient across the stomach and reducing the transpancreatic gradient. The studies raise the possibility that extrapancreatic glucagon may contribute to the hyperglucagonemia of insulin deficiency.

Animals↗
PubMed1976

Gastric A-cell function in normal dogs.

Glucagon release from the gastric fundus and pancreas were compared in normal dogs by measuring glucagon in plasma from a major gastroepiploic vein, the superior pancreaticoduodenal vein, and the inferior vena cava. In 32 dogs in the basal state, gastric vein glucagon averaged 97 +/- 40 pg/ml, not significantly different from the 93 +/- 41 pg/ml level in the vena cava. Pancreaticoduodenal vein glucagon averaged 250 +/- 32 pg/ml (P less than 0.001). Intravenous arginine infused in four dogs caused a rise in mean gastric vein glucagon to 210 +/- 33 pg/ml within 3 min, and glucagon remained between 53 and 98 pg/ml above the vena caval level thereafter. In the gastric vein, the rise in glucagon was significantly greater than in the vena cava at 3, 5, and 10 min (P less than 0.05), but was far less than in the pancreaticoduodenal vein where glucagon rose to 1,295 +/- 379 pg/ml at 1.5 min. Evidence of modest gastric glucagon release was observed after the intragastric instillation of arginine, but not during insulin or phloridzin-induced hypoglycemia. It was concluded that in normal dogs under the circumstances studied, the gastric fundus is not a major source of circulating glucagon.

Animals↗
PubMed1976

Development of insulin and glucagon binding and the adenylate cyclase response in liver membranes of the prenatal, postnatal, and adult rat: evidence of glucagon "resistance".

Although plasma glucagon levels in the rat fetus are in the adult range, hepatic glycogen is present in far greater abundance in the fetus than in the adult. To explain this paradox, adenylate cyclase response to glucagon was studied in partially purified membranes of rat livers obtained throughout perinatal life and at 3 months of age. The adenylate cyclase response to glucagon (10(-9) M) was only 7% of the adult response at day 15 of fetal life and 20% on the 21st day. No until after the 30th day postpartum did not reach maturity. Yet, the adenylate cyclase response to stimulation by NaF was comparable to the adult response throughout fetal life. The binding of [125I]iodoglucagon (2 X 10(-9) M) by these membrane preparations was only 1% of the adult level at day 15 of fetal life and increased to 23% at the 21st day, and, like the adenylate cyclase response to glucagon, did not reach maturity until after the 30th day of postnatal life. In contrast, insulin binding on the 15th day of gestation was 11% of the adult level and on the 21st day 45% of the adult level, reaching adult levels by the 30th postnatal day. An increase in membrane-associated particles, reflecting intramembranous protein, was observed during prenatal life, but the mean particle number per mum2 reached adult levels on the 21st day of fetal life, indicating that subsequent changes in hormone binding were clearly independent of non-specific changes in the number of particles. The findings suggest that the fetal liver is less sensitive to glucagon action than the adult liver, and that this glucagon "resistance" is mediated by a reduced capacity of the hepatocyte to bind glucagon at a time when substantial binding of insulin is demonstrable. Selective discrimination against glucagon may be important in promoting the anabolic processes required for normal fetal development.

Adenylyl Cyclases↗
PubMed1976

Gastric A-cell function in insulin-deprived depancreatized dogs.

To determine if gastric A-cells are a major source of the glucagonemia of insulin-deprived depancreatized dogs and to examine their secretory behavior, immunoreactive glucagon (IRG) was measured simultaneously in plasma from the inferior vena cava (VC) and from a gastric vein (GV) draining the fundus. Basal GV IRG averaged 205 +/- 35 pg/ml, significantly above the VC level of 71 +/- 30 (P less than 0.001) and rose to 1417 +/- 498 1.5 minutes after the start of an arginine infusion, exceeding VC IRG at all points (P less than 0.01). Measurement of IRG in gastric, jejunal, and ileal veins and vena cava revealed an IRG gradient only across the stomach. Measurement of glucagon-like immunoreactivity (GLI) revealed no gradient across the stomach, jejunum, or ileum, thus excluding cross-reaction with GLI as the cause of the GV hyperglucagonemia. Intragastric arginine elicited a near doubling of GV IRG within 1.5 minutes and this persisted for at least 120 minutes, ranging from 142 to 623 pg/ml above the VC level. Infusion of insulin at a physiologic rate lowered GV IRG from 665 +/- 66 to 151 +/- 49 pg/ml in 20 minutes and abolished the GV-VC gradient within 60 minutes, whereas intravenous and intragastric glucose administration without insulin did not alter GV IRG. It is concluded that: 1) in the insulin-deprived depancreatized dog, the stomach is a major source of IRG; 2) gastric IRG secretion is somehow stimulated by intravenous and intragastric arginine administration; 3) it is not influenced by intravenous or intragastric glucose administration; and 4) its release is suppressed by physiologic levels of insulin.

Animals↗