Acid Amyloglucosidase Research Articles

Acid amyloglucosidase and carbohydrate regulation. 3. The induction of sulphonylurea-stimulated insulin release and its dependence on intracellular monoamines.

The induction of sulphonylurea-stimulated insulin release and its dependence on intracellular monoamine levels in the β-cells was studied in mice. Model experiments in vitro on the interaction between monoamines and purified fungal acid amyloglucosidase were performed.1) Glibenclamide-induced hypoglycemia in mice was prolonged by pretreatment with a small dose of purified fungal acid amyloglucosidase, which itself did not influence the blood glucose level.2) Two minutes following the intravenous injection of glibenclamide, the "free" activity of acid amyloglucosidase in islet homogenates prepared in osmotically protected media was increased. This increase was found to be dose dependent.3) Glibenclamide-induced insulin release in adrenalectomized animals was significantly inhibited by pretreatment with the lysosomal stabilizer dexamethasone and significantly enhanced by pretreatment with the lysosomal labilizer progesterone.4) Glibenclamide-induced insulin release in animals pretreated with a small dose of purified fungal acid amyloglucosidase was considerably enhanced. This increase was significantly inhibited following administration of the monoamine precursors L-5-hydroxytryptophan (L-5-HTP) and L-3,4-dihydroxyphenylalanine (L-DOPA) and also after pretreatment with the non-hydrazine monoamine oxidase inhibitor pargyline. L-DOPA was found to be a more potent inhibitor than L-5-HTP. Combined treatment with pargyline and L-DOPA further decreased the response.5) Model experiments in vitro on the interaction between amines and acid amyloglucosidase activity (purified fungal acid amyloglucosidase) showed a pH-dependent inhibitory action of the monoamines dopamine (DA) and 5-hydroxytryptamine (5-HT) on amyloglucosidase activity. DA was more potent than 5-HT.6) From the data presented it is assumed that the induction of sulphonylurea-stimulated insulin release is elicited through the following events in the β-cell: Lysosomal activation - Increase of the "free" activity of the lysosomal acid amyloglucosidase - Hydrolytic glycogenosis through acid amyloglucosidase (reaction product: glucose) - Insulin release. From a functional point of view it is proposed that lysosomes taking part in insulin secreting processes should be designated crinosomes.

Acid Amyloglucosidase and Carbohydrate Regulation

High activity of the exoamylolytic enzyme, acid amyloglucosidase, was found in isolated pancreatic islets of the mouse. Enzyme activity was optimum at pH 5.0-5.5 and the activity at pH 5.0 was two times that of liver and ten times that of skeletal muscle. Acid amyloglucosidase activity in islets isolated from alloxan diabetic animals was reduced to about 10% of the normal value indicating that the major part of the enzyme activity is confined to islet β-cells. In contrast, islets isolated from insulin-hypersecreting obese mice (AO-mice) were found to have markedly elevated levels of acid amyloglucosidase activity.

Changes in islet glucan-1,4-α-glucosidase activity modulate sulphonylurea-induced but not cholinergic insulin secretion

We have previously presented indirect in vivo evidence for the involvement of islet acid glucan-1,4-α-glucosidase (acid amyloglucosidase), a lysosomal glucose-producing enzyme, in certain insulin secretory processes. In the present in vitro and in vivo investigation, we studied whether differential changes in islet acid amyloglucosidase activity would be related to the insulin secretory response induced by two mechanistically different secretagogues, the sulphonylurea derivative, glibenclamide and the acetylcholine receptor agonist, carbachol. It was observed that the selective α-glucosidehydrolase inhibitors emiglitate and acarbose markedly reduced glibenclamide-induced insulin release from isolated islets. Insulin release stimulated by carbachol or the protein kinase C activator TPA (12- O-tetradecanoylphorbol 13-acetate), was not inhibited. Basal insulin secretion was unaffected by emiglitate and acarbose. Further, pretreatment of mice with emiglitate resulted in a marked reduction of the in vivo insulin response to glibenclamide. Moreover, in vivo pretreatment with purified fungal amylglucosidase (‘enzyme replacement’), a procedure known to increase islet amyloglucosidase activity, greatly enhanced the insulin response to i.v. glibenclamide. This insulin release was accompanied by a marked depression of the blood glucose levels. In contrast, enzyme pretreatment did not influence the insulin response or the blood glucose levels after carbachol. The data strongly suggest that islet acid amyloglucosidase is involved in the insulin secretory processes induced by glibenclamide but not in those involving stimulation of muscarinic receptors or direct activation of protein kinase C. The results also indicate separate or at least partially separate pathways for insulin release induced by glibenclamide and cholinergic stimulation.

Islet glucan-1,4-alpha-glucosidase: differential influence on insulin secretion induced by glucose and isobutylmethylxanthine in mice.

In previous in-vivo studies we have presented indirect evidence for the involvement of islet acid glucan-1,4-alpha-glucosidase (acid amyloglucosidase), a lysosomal glycogen-hydrolysing enzyme, in certain insulin secretory processes. In the present combined in-vitro and in-vivo investigation, we studied whether differential changes in islet acid amyloglucosidase activity were related to the insulin secretory response induced by two mechanistically different secretagogues, glucose and isobutylmethylxanthine (IBMX). It was observed that addition of the selective alpha-glucosidehydrolase inhibitor emiglitate (1 mmol/l) to isolated pancreatic islets resulted in a marked reduction of glucose-induced insulin release. This was accompanied by a pronounced suppression of islet activities of acid amyloglucosidase and acid alpha-glucosidase, whereas other lysosomal enzyme activities, such as acid phosphatase and N-acetyl-beta-D-glucosaminidase, were unaffected. Furthermore, islets first incubated with emiglitate in the presence of high (16.7 mmol/l) glucose released less insulin than untreated controls in response to glucose in a second incubation period in the absence of emiglitate. In contrast, IBMX-induced insulin release was not influenced by emiglitate although accompanied by a marked reduction of islet activities of all three alpha-glucosidehydrolases. Basal insulin secretion (1 mmol glucose/l) was unaffected in the presence of emiglitate. In-vivo pretreatment of mice with highly purified fungal amyloglucosidase ('enzyme replacement'), a procedure known to increase islet amyloglucosidase activity, resulted in a greatly enhanced insulin secretory response to an i.v. glucose load. The increase in insulin release was accompanied by a markedly improved glucose tolerance curve in these animals. In contrast, enzyme pretreatment did not influence the insulin response or the blood glucose levels after an i.v. injection of IBMX. The data lend further support to our hypothesis that islet acid amyloglucosidase is involved in the multifactorial insulin secretory processes induced by glucose but not in those involving direct activation of the cyclic AMP system. The results also indicate separate, or at least partially separate, pathways for insulin release induced by glucose and IBMX.

Ca2+ deficiency, selective alpha-glucosidehydrolase inhibition, and insulin secretion

We investigated the relation between activities of islet glycogenolytic alpha-glucosidehydrolases and insulin secretion induced by glucose and 3-isobutyl-1-methylxanthine (IBMX) by means of suppressing 1) insulin release (Ca2+ deficiency) and 2) islet alpha-glucosidehydrolase activity (selective inhibition by the deoxynojirimycin derivative miglitol). Additionally, the in vivo insulin response to both secretagogues was examined. We observed that, similar to glucose-induced insulin release, islet glycogenolytic hydrolases (acid amyloglucosidase, acid alpha-glucosidase) were highly Ca2+ dependent. Acid phosphatase, N-acetyl-beta-D-glucosaminidase, or neutral alpha-glucosidase (endoplasmic reticulum) was not influenced by Ca2+ deficiency. In Ca2+ deficiency IBMX-induced insulin release was unaffected and was accompanied by reduced activities of islet alpha-glucosidehydrolases. Miglitol strongly inhibited glucose-induced insulin release concomitant with a marked suppression of islet alpha-glucosidehydrolase activities. Direct addition of miglitol to islet homogenates suppressed acid amyloglucosidase [half-maximal effective concentration (EC50) approximately 10(-6) M] and acid alpha-glucosidase. Acid phosphatase and N-acetyl-beta-D-glucosaminidase were unaffected. The miglitol-induced inhibition of glucose-stimulated insulin release was dose dependent (EC50 approximately 10(-6) M) and displayed a remarkable parallelism with the inhibition curve for acid amyloglucosidase. The in vivo insulin secretory response to glucose was markedly reduced in dystrophic mice (low amyloglucosidase), whereas the response to IBMX was unaffected. In summary, islet glycogenolytic hydrolases are Ca2+ dependent, and acid amyloglucosidase is directly involved in the multifactorial process of glucose-induced insulin release. In contrast the mechanisms of IBMX-stimulated insulin secretion operate independently of these enzymes. The effects of miglitol, a drug currently used in diabetes therapy, deserves further investigation.

The relationship of islet amyloglucosidase activity and glucose-induced insulin secretion.

We have previously presented evidence for the involvement of islet acid amyloglucosidase, a lysosomal glycogen-hydrolyzing enzyme, in certain insulin secretory processes. In the present investigation, we studied whether differential changes in islet amyloglucosidase activity could be related to the insulin secretory response to glucose. It was observed that the dose-response curve for glucose-induced insulin response in vivo was shifted to the left by pretreatment of mice with purified fungal amyloglucosidase. In enzyme-pretreated mice, the ED50 was 2.1 mmol/kg glucose as compared with 5.7 mmol/kg in saline-pretreated controls (p less than 0.005). Also, the maximal insulin response to glucose was enhanced by amyloglucosidase pretreatment. Parenteral administration to mice (four injections during 2 days) of the pseudotetrasaccharide acarbose, a recognized inhibitor of intestinal alpha-glucosidases, surprisingly induced a marked increase in the activities of islet acid amyloglucosidase (+ 120%; p less than 0.001) and acid alpha-glucosidase (+ 45%; p less than 0.01) without affecting the activities of other lysosomal enzymes such as acid phosphatase and N-acetyl-beta-D-glucosaminidase. No effect on the microsomal neutral alpha-glucosidase was recorded. Moreover, in these mice, the insulin secretory response to glucose was enhanced both at a maximal dose of glucose 11.1 mmol/kg and at a dose in the ED25-ED50 range, 3.3 mmol/kg (p less than 0.005). Direct addition of acarbose to islet homogenates strongly suppressed acid amyloglucosidase activity, the EC50 being approximately 1 microM. Acid alpha-glucosidase activity was also strongly inhibited, whereas the activities of acid phosphatase and N-acetyl-beta-D-glucosaminidase were unaffected. Neutral alpha-glucosidase was slightly suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of the Lysosomotropic Drug Suramin on Islet Lysosomal Enzyme Activities and the Insulin-Secretory Response Induced by Various Secretagogues

The trypanocidal drug suramin is known to concentrate in lysosomes and to depress the activity of different lysosomal enzymes. We have previously shown that suramin can inhibit the activity of the islet lysosomal enzyme acid amyloglucosidase, a glycogenolytic glucose-producing hydrolase, which seems to be involved in certain insulin-secretory processes. In the present investigation we studied the pH dependency and dose-response effects of suramin on islet lysosomal enzyme activities as well as the effect of suramin treatment on the insulin-secretory response to various secretagogues in mice. It was found that two injections of suramin (0.18 mmol/kg) to normal NMRI mice at -24 and -2 h induced a moderate depression of the activities of islet acid amyloglucosidase (-22%) and acid phosphatase (-13%), whereas no effect was recorded for the activities of acid alpha-glucosidase, N-acetyl-beta-D-glucosaminidase and the non-lysosomal enzyme neutral alpha-glucosidase. Direct addition of different concentrations of suramin to islet homogenates showed that the drug was a potent inhibitor of acid amyloglucosidase and acid alpha-glucosidase at pH 4.0. At pH 5.0, suramin induced a large increase in acid alpha-glucosidase activity, whereas acid amyloglucosidase and acid phosphatase were inhibited. Suramin-injected mice showed a reduced insulin-secretory response to the sulphonylurea drug glibenclamide (-45%), whereas the insulin response to the cholinergic agonist carbachol or the phosphodiesterase inhibitor IBMX (1-isobutyl-3-methylxanthine) was unaffected. It is concluded that suramin inhibits islet acid amyloglucosidase activity in vivo and in vitro, whereas its effect on acid alpha-glucosidase is complex and pH dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin secretion and islet lysosomal enzyme activities in the mouse

To study the functional role of the lysosomes in islet physiology, we have in the present study investigated influences on insulin secretion induced by a primary inhibition of islet lysosomal enzyme activities by the use of the lysosomotropic drug suramin. First, we demonstrated that the activities of the three lysosomal enzymes, acid amyloglucosidase, acid alpha-glucosidase, and N-acetyl-beta-D-glucosaminidase, were inhibited in mouse islet homogenates upon direct addition of suramin (p less than 0.001). Thereafter, we studied the influences of suramin on islet lysosomal enzyme activities at 24 h after an administration of suramin to mice. We thereby found that the islet lysosomal enzyme activities were not significantly altered compared to controls. However, after incubation of the islets at 3.3 mM glucose, the activities of acid amyloglucosidase and acid alpha-glucosidase were increased (p less than 0.05). The activity of N-acetyl-beta-D-glucosaminidase was, however, not affected. Hence, the direct inhibitory action on islet lysosomal enzyme activities by suramin seems to be counteracted in vivo. Concurrently with the increased enzyme activities in incubated islets, glucose-induced insulin secretion was significantly potentiated by suramin pretreatment (p less than 0.01). In contrast, suramin pretreatment did impair the glucose-induced insulin secretion in vivo (p less than 0.01). The direct effects on plasma insulin and glucose levels of acutely administered suramin were also studied. It was found that at a high dose level, suramin slightly reduced the basal plasma insulin levels (p less than 0.05). Suramin did not, however, affect the glucose-induced increase in plasma insulin levels. Conversely, at a low dose level, suramin potentiated glucose-induced increase in plasma insulin levels (p less than 0.01). A similar potentiated glucose-induced insulin secretion by suramin was also observed by a direct addition of the drug to islets in vitro. In conclusion, this study demonstrates that suramin inhibits lysosomal enzyme activities in islet homogenates, increases the activity of acid amyloglucosidase and acid alpha-glucosidase in incubated mouse islets after administration of the drug in vivo and potentiates glucose-stimulated insulin secretion from islets in vitro after administration of the drug in vivo. Thus, we suggest first, that in vivo, compensatory mechanisms may counteract the direct inhibitory influence of suramin on islet lysosomal enzyme activities, and second, that in vitro, islet lysosomal acid amyloglucosidase and acid alpha-glucosidase activities and glucose-induced insulin secretion are regulated in parallel.

Lysosomal enzyme activities in pancreatic islets from normal and obese hyperglycemic mice

Lysosomal enzyme activities in pancreatic islets of obese hyperglycemic ob ob mice aged 3 to 6 months were investigated and compared with those of normal lean NMRI mice of the same age. It was observed that the glycogenolytic glucose-producing hydrolase acid amyloglucosidase displayed a fivefold higher activity in the islets of obese mice than in the islets of normal NMRI mice. However, other islet lysosomal enzyme activities measured, such as N-acetyl-β-D-glucosaminidase and β-glucuronidase, were of the same magnitude in both obese and lean mice. A starvation period of 24 hours induced a significant depression of islet acid amyloglucosidase activity in obese as well as lean mice, whereas the activities of N-acetyl-β-D-glucosaminidase and β-glucuronidase were unaffected. Further, the activities of other types of islet lysosomal enzymes, such as acid phosphatase and cathepsin D, were also measured in obese mice. These activities were not found to be affected by the actual fasting period. A good correlation ( r = 0.815; P < 0.01) was observed between islet acid amyloglucosidase activity and plasma insulin concentrations in obese mice, whereas no such relationship was apparent with regard to other islet lysosomal enzyme activities recorded. Acid amyloglucosidase activity in liver tissue of the obese mouse was about 30 times lower than that of islet tissue. Further, the activity of liver amyloglucosidase was of the same order of magnitude in obese and lean mice. Similarly, other lysosomal enzyme activities in the liver of obese and lean mice were not strikingly different. After administration of purified fungal amyloglucosidase to normal mice, it was taken up by both islet and liver tissue. The time-courses of the action of the enzyme to increase glucose-stimulated insulin response and to depress liver glycogen levels were in accordance with each other. The effect on insulin secretion was not detectable until one and a half hours after enzyme injection and vanished after six to eight hours, suggesting that the enzyme exerts its action intracellularly, probably via the vacuolar system. A dose-response relationship between glucose-stimulated insulin response and dosage of exogenous amyloglucosidase was established and the exogenous enzyme could be shown to restore the fasting-induced impairment of insulin release after an IV glucose load. This restoration was reflected in a markedly improved glucose-tolerance curve. Intravenous injection to normal mice of a maximal dose of glucose increased the “free” activity of islet acid amyloglucosidase by about 20% but did not affect the free activity of β-glucuronidase at two minutes after injection, ie, at the time of maximal insulin response. Cholinergic stimulation by the muscarinic agonist carbachol, inducing a similar increase in insulin release, did not affect the “free” activity of either amyloglucosidase or β-glucuronidase. The data suggest that a specialized lysosome population may be involved in certain insulin secretory processes through the action of the lysosomal enzyme acid amyloglucosidase and that the extremely high activity of islet amyloglucosidase in the obese mouse may contribute to the high insulin secretory rate in these animals. The action of islet amyloglucosidase is not only regulated by changes in the total activity of the enzyme but apparently also by changes in its latency properties (relation “free” to “latent” activity) probably exerted through lysosomal labilization-stabilization perturbations.

Effect of fasting on islet lysosomal enzyme activities and the in vivo insulin response to different secretagogues.

The effect of a 24 hr starvation period on islet lysosomal enzyme activities and the in vivo insulin response to glucose, glibenclamide and L-isopropyl-noradrenaline (L-IPNA) was studied in mice. It was observed that fasting induced a significant decrease of islet acid amyloglucosidase activity, whereas the activities of acid phosphatase, beta-N-acetyl-glucosaminidase, and beta-glucuronidase in islet tissue were unaffected by the fasting period studied. Starvation markedly reduced the acute insulin response to a maximal dose of glucose or glibenclamide. However, the insulin response to a maximal dose of L-IPNA was of similar magnitude in both fed and fasted animals. Pretreatment of fasted mice with purified fungal acid amyloglucosidase could restore the impaired insulin response to glucose to the normal level seen in fed mice. It is suggested that islet acid amyloglucosidase activity is of importance for glucose-stimulated insulin secretion, and that reduced levels of islet amyloglucosidase may contribute to the impairment of glucose-induced insulin release seen after fasting.

Cholinergic muscarinic effects on insulin release in mice.

Insulin secretion and blood glucose homeostasis were studied in mice following administration of cholinergic agonists, antagonists and other possible modifiers of cholinergic insulin secretory mechanisms. It was observed that administration to mice of the cholinergic agonists acetylcholine, carbachol and pilocarpine resulted in an increase in plasma immuno-reactive insulin levels accompanied by a significant fall in blood glucose levels. Nicotine had no effect. Carbachol was found to enhance insulin release in a dose-dependent manner. Muscarinic blockade by atropine or methylatropine totally suppressed carbachol-induced insulin secretion. No blocking effect was accomplished by beta-adrenoceptor blockade. Glucose-induced insulin secretion was not affected by atropine in normal non-fasted mice. In mice fasted for 24 h, however, the insulin response to glucose was impaired by atropine suggesting that the nutritional state is important for cholinergic modulation of glucose-induced insulin response. Pretreatment of animals with the glycogenolytic hydrolase, acid amyloglucosidase, enhanced tolbutamide-induced insulin release but did not influence insulin secretion stimulated by carbachol. Pretreatment with the monoamine oxidase inhibitor, pargyline, plus L-dopa, leading to an intracellular accumulation of dopamine in the insulin cells, totally suppressed carbachol-induced insulin release. It is suggested that, in mice, cholinergic stimulation promotes insulin secretion through activation of muscarinic receptors on the insulin cell. Blockade of these receptors does not influence glucose-stimulated insulin release in the non-fasting state, but may impair the insulin response to glucose after fasting. Cholinergic stimulation of insulin release is inhibited after L-dopa-induced accumulation of dopamine in the insulin cells. In contrast to tolbutamide-induced insulin release cholinergic insulin release is not dependent on acid amyloglucosidase activity.

Insulin secretion and carbohydrate metabolism in the dystrophic mouse

Dystrophic mice were investigated with regard to their regulation of blood glucose and insulin secretion in vivo. The following were also measured: tissue glycogen levels, activity of the glycogenolytic hydrolase, acid amyloglucosidase, and in vitro glucose utilization by liver, muscle and adipose tissue. Basal levels of blood glucose and plasma insulin of dystrophic mice were essentially within the same range as in the clinically unaffected littermate controls. Dystrophic mice had a decreased tolerance to glucose and glibenclamide; the secretion of insulin in response to these secretagogues was moderately reduced. Insulin release following β-adrenergic stimulation, however, was increased in the dystrophic mice. Glycogen levels and acid amyloglucosidase activity were increased in dystrophic muscles but were normal in liver. Acid amyloglucosidase activity in pancreatic islets was lower in the dystrophic mouse. Glucose utilization in vitro appeared normal in liver tissue from dystrophic mice; in dystrophic muscle there was a threefold increase in 14CO 2-production with no concomitant increase in either glycogen or 14C-incorporation into glycogen. 14CO 2 production and 14C-incorporation into lipid and glycogen were increased in dystrophic adipose tissue. We suggest that the decreased glucose tolerance, and the reduced insulin response to glucose in the dystrophic mouse are compensated by an increased glucose utilization in muscle and adipose tissue and an increased β-adrenergic-mediated secretion of insulin.

Pattern of Islet Lysosomal Enzyme Activities and Insulin Secretory Response

The pattern of lysosomal enzyme activities in isolated pancreatic islets was studied in 3 different strains of mice, NMRI, CBA, and C-57, and related to the in vivo insulin release following injection of the insulin scretagogues glucose and carbachol. It was observed that the relative specific activities among the islet enzymes studied did not show the same pattern in the different strains although beta-gluc-ronidase always displayed the lowest activity. Comparison between the strains revealed that acid phosphatase activity was of the same magnitude in all 3 strains. Islet activities of acid amyloglucosidase, beta-glucuronidase, and N-acetylglucosaminidase, however, were largest in NMRI, intermediate in CBA, and lowest in C-57. This activity pattern roughly correlated with the insulin secretory response to an intravenous injection of glucose, whereas insulin release induced by the cholinergic agonist carbachol was of similar magnitude in all strains.

Carbohydrate Content and Regulation following Injection of Different Glycogenolytic Enzymes

The effect of injection of glycogenolytic enzymes on tissue glycogen, blood glucose and plasma insulin was studied in mice. No effects were observed following phosphorylase, whereas the hydrolytic enzymes, alpha-amylase and acid amyloglucosidase depressed liver glycogen. In addition acid amyloglucosidase induced a decrease in blood glucose, a slight elevation of plasma insulin and a marked increase in tolbutamide-stimulated insulin release. At the doses given none of the enzymes affected muscle glycogen. Amyloglucosidase pretreatment markedly enhanced insulin release induced by glibenclamide, leucine, isoleucine, lysine and glucose whereas insulin release stimulated by IPNA, ACTH, glucagon and "CCK-PZ" was unaffected. Injection of acid amyloglucosidase has a profound influence on carbohydrate content and regulation in mice. It is suggested that the dependence or independence of amyloglucosidase activity among the insulin secretagogues tested might reflect different or partially different mechanisms in the process of insulin secretion.

Islet Amyloglucosidase and Sulphonylurea-Stimulated Insulin Release in Three Different Strains of Mice

The activities of the lysosomal enzymes acid amyloglucosidase and β-glucuronidase were assayed in isolated pancreatic islets and liver tissue from three different strains of mice. It was observed that acid amyloglucosidase activity in islets isolated from the CBA-strain and the C-57 strain was only 44% and 36% respectively of the activity recorded in the NMRI-strain. β-Glucuronidase activity displayed a similar pattern. In liver tissue the activities of the two lysosomal enzymes displayed a different pattern. The highest activities of acid amyloglucosidase and β--glucuronidase in the liver were observed in the C-57 strain while the other two strains showed slightly lower activities. There was no difference between the three strains with regard to basal plasma insulin levels and thus no apparent relation to the activities of the lysosomal enzymes in the islets. However, the insulin releasing capacity in the three different strains following an intravenous injection of a maximal dose of the sulphonylurea compound, glibenclamide, roughly correlated with islet amyloglucosidase activity while a similar stimulation by the β-adrenergic agonist L-isopropylnoradrenaline (L-IPNA) elicited an insulin response of equal magnitude in all three strains. It is suggested that acute sulphonylureastimulated insulin release is dependent on islet amyloglucosidase activity while β-adrenergic stimulation of insulin release is independent of the activity of this enzyme.

Acid amyloglucosidase in human fetal liver during acute asphyxia.

Acid amyloglucosidase activity in human fetal liver was found to display latency. Increase of ‘&lt;i&gt;free&lt;/i&gt;’ enzyme activity was elicited &lt;i&gt;in vitro&lt;/i&gt; by lowering of homogenate osmolarity or addition of detergent. A moderate but highly significant rise in the ‘&lt;i&gt;free&lt;/i&gt;’ enzyme activity of the liver was found after in vivo exposition to 10 min of asphyxia. It is suggested that the increase of hepatic ‘&lt;i&gt;free&lt;/i&gt;’ acid amyloglucosidase activity during acute asphyxia might be of significant relevance for the knowledge of the mechanisms behind the accompanying rise of plasma glucose and hepatic glucose production.

A cid amyloglucosidase and carbohydrate regulation. I. Effect of exogenous amyloglucosidase on tissue glycogen, blood glucose and plasma insulin.

In the paper by I. Lundquist (Horm. Metab. Res. 4: 151-158, 1972) Figure I B was misprinted. The correct figure looks as follows:

ACID AMYLOGLUCOSIDASE AND INSULIN SECRETION

Acta Physiologica ScandinavicaVolume 84, Issue s372 p. 28-34 ACID AMYLOGLUCOSIDASE AND INSULIN SECRETION First published: May 1971 https://doi.org/10.1111/j.1748-1716.1971.tb05220.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume84, Issues372May 1971Pages 28-34 RelatedInformation

Is there a common beta cell insulin compartment stimulated by glucose and tolbutamide?

ARTICLESIs there a common beta cell insulin compartment stimulated by glucose and tolbutamide?DL CurryDL CurryPublished Online:01 Feb 1971https://doi.org/10.1152/ajplegacy.1971.220.2.319MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByStimulation of insulin secretion by beta-endorphins (I-27 & I-31)Life Sciences, Vol. 40, No. 21Interaction of sulfonylurea with the pancreatic B-cellExperientia, Vol. 40, No. 10Insulin secretory dynamics after two consecutive intravenous stimulations with glucose and/or tolbutamideMetabolism, Vol. 28, No. 12Early insulin and glucagon response to subsequent pulses of arginine, glucose, and tolbutamide in normal man.A V Greco, R Manna, G Ghirlanda, L Altomonte, A G Rebuzzi, and A Bertoli1 February 1979 | American Journal of Physiology-Endocrinology and Metabolism, Vol. 236, No. 2Duplication of the blood glucose curve of an OGTT in dogs by a prospectively programmed I.V. infusion: Infusion pattern and IRI responseActa Diabetologica Latina, Vol. 15, No. 5-6The Kinetics of Insulin ReleaseEffects of Sulfonylurea Derivatives on Pancreatic β-CellsThe immediate insulin secretory response of the isolated perfused rat pancreas to tolbutamide and glucose19 October 2001 | FEBS Letters, Vol. 49, No. 3Significance of acid amyloglucosidase in sulphonylurea-induced insulin releaseDiabetologia, Vol. 10, No. 6L-Leucine and l-phenylalanine induced insulin release and the influence of D-glucoseDiabetologia, Vol. 10, No. 5Dynamics of pancreatic ?-cell responses to glucoseDiabetologia, Vol. 9, No. 5Chapter 19. Anti-Diabetic Agents More from this issue > Volume 220Issue 2February 1971Pages 319-323 Copyright & PermissionsCopyright © 1971 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1971.220.2.319PubMed5540877History Published online 1 February 1971 Published in print 1 February 1971 Metrics

Method for determination of acid amyloglucosidase in isolated islets of the pancreas.

Method for determination of acid amyloglucosidase in isolated islets of the pancreas.