Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Addition of the cyclic AMP phosphodiesterase inhibitors theophylline (10- minus 2 M) or papaverine (10- minus 4 M) leads to a complete inhibition of lactose synthesis in incubated guinea pig mammary gland slices. Addition of 10- minus 5 M cyclic AMP or dibutyryl cyclic AMP results in 1 30-40% inhibition of the synthesis, which effect is not increased by applying higher concentrations of these compounds. A 30-40% inhibition can also be obtained with epinephrine (5 - 10- minus 5 M), or isoproterenol (10- minus 4 M), but the polypeptide hormones glucagon (10- minus 7 M), insulin (1 munit/ml) and relaxin (10 mug/ml) do not significantly affect lactose synthesis. Cytochalasin B (5 mug/ml) inhibits lactose production by 58and colchicine (10- minus 5 M) by 25%. These experiments suggest that an increase in the intracellular level of cyclic AMP either through its addition, through hormonal stimulation of its synthesis, or through inhibition of its intracellular breakdown, leads to an inhibition of lactose production in lactating mammary gland. This effect of cyclic AMP is similar to that of progesterone, which is known to inhibit lactation in vivo and the withdrawal of which at parturition has been postulated to initiate lactogenesis.
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PMID:Inhibition by cyclic AMP of lactose production in lactating guinea pig mammary gland slices. 16 55

We studied the release of insulin, glucagon, and somatostatin in response to glucose, glyceraldehyde (GA), and alpha-ketoisocaproate (KIC) from rat kidneys containing transplanted insulinomas. Kidneys were perfused about 11 wk after transplantation when the plasma glucose concentration of the fed animals had decreased from 180 +/- 7 to 95.1 +/- 9.9 mg/dl and plasma insulin concentrations had increased from 2.6 +/- 0.5 to 14.2 +/- 2.0 ng/ml. The insulin content of the tumor-containing kidney ranged from 40 to 679 micrograms; the glucagon and somatostatin concentrations ranged from undetectable levels to 3.7 micrograms and 248 ng, respectively. The average response to 30 mM glucose and 10 mM GA was a four- to fivefold increase in insulin secretion, whereas 30 mM KIC caused a 16- to 28-fold increase. In vitro stimulation of the insulinoma with 30 mM glucose primed the beta-cell response to a second stimulus following a short rest period. Cytochalasin B did not enhance this primed glucose response. Diazoxide inhibited glucose, GA, and KIC-stimulated insulin release. Glucose, GA, and KIC stimulated glucagon release in 2 of 17 insulinomas studied here. Somatostatin release was not seen in any of the experiments. These findings show that this islet cell tumor transplanted under the kidney capsule releases insulin in response to physiologic and model fuel substances. Thus, this particular transplantable tumor offers an opportunity to study the biochemistry and biophysics that underlie fuel-stimulated insulin release.
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PMID:Fuel-induced insulin release in vitro from insulinomas transplanted into the rat kidney. 614 Jan 99

1. Effect of glucagon on amylase secretion and lactic dehydrogenase (LDH) release from functionally intact dissociated pancreatic acinar cells and acini was studied. 2. In dissociated rat pancreatic acinar cells, the rate of amylase secretion was increased by 70% with bethanechol (maximally effective concentration, 10(-4) M) and 125% with A23187 (10(-5) M), but the response to cholecystokinin-pancreozymin (CCK-PZ) was inconsistent. In dissociated cells from mouse pancreas, the increases amounted to 78% with bethanechol (10(-4) M), 134% with A23187 (10(-5) M) and 82% with CCK-PZ (maximally effective concentration, 0 . 01 u. ml.-1). Glucagon in concentrations ranging from 10(-7) to 10(-4) M increased amylase secretion by 3, 26, 67 and 80%, whereas secretin (10(-8)--10(-5) M) increased amylase secretion by 8, 39, 88 and 138%. LDH release was increased with A23187 in concentrations greater than 10(-6) M. 3. CCK-PZ, bethanechol and A23187 used in maximal concentrations potentiated the effect of a submaximal dose of glucagon whereas secretin did not have an additive or a potentiating effect. 4. Pancreatic acini were approximately 3 times more responsive to secretagogues than cells. The dose--response curves to bethanechol, glucagon and CCK-PZ for increase in amylase secretion were similar. LDH release was not increased by these agents. Cytochalasin B (5 microgram ml.-1) which is known to disrupt the integrity of luminal membrane inhibited the amylase secretion stimulated by glucagon, bethanechol and CCK-PZ. 5. Glucagon inhibited incorporation of a mixture of fifteen 14C-labelled amino acids (algal profile, Schwarz Mann) into perchloric acid precipitable proteins in dissociated mouse pancreatic acini within 30 min. 6. In 'pulse-chase' experiments, glucagon decreased the specific activity of zymogen granules isolated by differential centrifugation, from pancreatic lobules (120 min) and increased the specific activity of radiolabelled proteins in the medium (60 and 120 min). 7. It is concluded that glucagon increased digestive enzyme secretion from pancreatic acinar cells by a direct action (in contrast to its reported indirect effect in vivo) and decreased digestive enzyme synthesis. The data on transport and secretion do not support the suggested role of glucagon as an inhibitor in the intact animal.
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PMID:Effect of glucagon on digestive enzyme synthesis, transport and secretion in mouse pancreatic acinar cells. 616 27

We examined the uptake of 3-O-methyl-D-glucose, a nonmetabolizable hexose, by isolated rat hepatocytes. The uptake of 3-O-methyl-D-glucose was linear for 1 min at 22 degrees, and Lineweaver-Burk analysis demonstrated an apparent Km of approximately 6 mM. Cytochalasin B (40 microM) and phloridzin (2 mM) inhibited 3-O-methyl-D-glucose uptake by 88% and 63%, respectively. D-Glucose (20 mM) inhibited the initial rate of 3-O-methyl-D-glucose uptake by 55% (p less than 0.001), whereas L-glucose was without any significant effect. The uptake of 3-O-methyl-D-glucose remained unchanged in the presence of Na+ (0-150 mM) in the incubation medium. After 30 min dexamethasone inhibited glucose uptake (the maximal effect being achieved in a time- and concentration-dependent manner) at 2 microM and 0.5 microM concentrations by 50% and 25%, respectively. Dexamethasone produced a decrease in the Vmax but did not change the Km. Insulin, glucagon, gastric inhibitory polypeptides, and pancreozymin had no effect on 3-O-methyl-D-glucose uptake in isolated hepatocytes. These findings are consistent with the conclusion that 3-O-methyl-D-glucose uptake in isolated rat hepatocytes occurs via a stereospecific, carrier-mediated, facilitated diffusion process. Dexamethasone decreases this process of facilitated diffusion in the isolated hepatocyte.
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PMID:3-O-methyl-D-glucose uptake in isolated rat hepatocytes. Effects of dexamethasone. 686 98

Cytochalasin B is known to enhance insulin release evoked by nutrient and non-nutrient secretagogues, including D-glucose, despite inhibiting D-glucose uptake and metabolism in pancreatic islets. In the present study, cytochalasin D, which failed to affect D-glucose uptake and metabolism by isolated islets, also augmented glucose-stimulated insulin release, but unexpectedly to a lesser extent than cytochalasin B. Such was not the case, however, in islets stimulated by non-glucidic nutrients such as 2-ketoisocaproate or the association of L-leucine and L-glutamine. This situation coincided with the fact that cytochalasin B inhibited more severely D-glucose metabolism in non-B, as distinct from B, islet cells and, in the former case, caused a relatively greater inhibition of hexose catabolism at 2.8 mM than at 16.7 mM D-glucose. Nevertheless, even in the presence of forskolin, cytochalasin B was more efficient than cytochalasin D in augmenting glucose-stimulated insulin secretion. Thus, although these data document that non-B islet cells are more sensitive than purified islet B cells to cytochalasin B, at least in terms of inhibition of D-glucose catabolism, such a difference and its possible consequence upon the release of glucagon and other non-insulinic hormones by non-B islet cells do not appear sufficient to account for the greater enhancing action of cytochalasin B, as distinct from cytochalasin D, upon glucose-stimulated insulin output. Likewise, the latter difference does not appear attributable to a greater efficiency of cytochalasin B, as compared to cytochalasin D, upon the mechanical events involved in nutrient-stimulated exocytosis of insulin granules. Hence, the present findings suggest a so-far-unidentified interference of cytochalasin B with the B-cell glucose-sensing device.
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PMID:Effects of cytochalasin B and D upon insulin release and pancreatic islet cell metabolism. 1178 28