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DOI: 10.1055/s-2006-947199
© Georg Thieme Verlag KG Stuttgart · New York
Antihyperglycemic Effect of Aporphines and their Derivatives in Normal and Diabetic Rats
M. J. Su, Ph. D.
Institute of Pharmacology
College of Medicine
National Taiwan University
No. K1, Sec. 1, Jen-Ai Rd
Taipei
Taiwan
Republic of China
Phone: +886-2-2312-3456 ext. 8317
Fax: +886-2-2397-1403
Email: mjsu@ha.mc.ntu.edu.tw
Publication History
Received: October 28, 2005
Accepted: June 2, 2006
Publication Date:
21 August 2006 (online)
Abstract
The antihyperglycemic actions of some aporphines and their derivatives in normal Wistar, streptozotocin (STZ)-induced diabetic (IDDM) and nicotinamide-STZ induced diabetic (NIDDM) rats were investigated in this study. These compounds included thaliporphine, glaucine, boldine, N-methyllaurotetanine, and predicentrine and the derivatives, N-[2-(2-methoxyphenoxy)ethyl]norglaucine and diacetyl-N-allylsecoboldine. Bolus intravenous injection of these compounds decreased the plasma glucose levels in a dose-dependent manner in both normal and diabetic rats. Among them, thaliporphine was found to have the most potent antihyperglycemic effect in both NIDDM and IDDM diabetic rats. It was found that thaliporphine could stimulate the release of insulin in both normal and diabetic rats, and a dose of 1 mg per kg thaliporphine could significantly attenuate the increase of plasma glucose induced by an intravenous glucose challenge test in normal rats. Similar treatment with thaliporphine significantly increased the skeletal muscle glycogen synthesis in both normal and diabetic rats. Hence, the hypoglycemic effect of thaliporphine in diabetic rats could be attributed to the stimulation of insulin release and the increase of glucose utilization.
#Introduction
Diabetes, which ranks highly among the top ten causes of mortality worldwide, often leads to disability from vascular complications and limb amputation in addition to neurological complications and premature death [1]. The incidence of acute myocardial infarction associated with arrhythmia is high in the population of diabetes mellitus (DM) disease. Therefore, the aim was to find a new antidiabetic agent with antiarrhythmic activity. The aporphines, including thaliporphine, glaucine, boldine, N-methyllaurotetanine, and predicentrine, and the aporphine derivatives, N-[2-(2-methoxyphenoxy)ethyl]glaucine and diacetyl-N-allylsecoboldine (Fig. [1]), isolated from Lauraceous plants or by chemical preparation [2], [3], [4], [5], had been reported to exhibit antiarrhythmic activity in ischemia-reperfusion rat hearts in vivo [6], [7]. The present study was aimed to find out whether they possessed hypoglycemic activities in normal Wistar rats, streptozotocin (STZ)-induced diabetic and nicotinamide-STZ-induced diabetic rats, the latter two representing insulin-dependent DM (IDDM) and non insulin-dependent DM (NIDDM) animal models, respectively.
Fig. 1 The chemical structures of aporphines and aporphine derivatives in the present study.
Materials and Methods
#Chemicals
Thaliporphine and N-methyllaurotetanine were obtained from glaucine which, in turn, was prepared by reacting boldine with N-trimethylanilinium iodide under alkaline conditions [5], a reaction that also yielded predicentrine due to incomplete O-methylation with hydrogen bromide [2]. Diacetyl-N-allylsecoboldine was prepared by O,O-acetylation of N-allylsecoboldine (Ac2O/pyridine), which was synthesized from boldine and allyl bromide under reflux [3]. N-[2-(2-Methoxyphenoxy)ethyl]glaucine was prepared from norglaucine [5] and (2-methoxyphenoxy)acetaldehyde by reductive N-alkylation (NaCNBH3, MeOH). All compounds were essentially pure by TLC and 1H-NMR.
#Animals
In this study, we used male Wistar rats, weighing 250 - 300 g, as our laboratory animals. The rats were supplied by the Medical School Animal Center, National Taiwan University. Insulin-dependent diabetes mellitus (IDDM) rats were induced according to the previous method [8]. In brief, an intravenous injection of STZ (Sigma Chemical Co.; St. Louis, MO, USA) at 60 mg kg-1 dissolved in 1 % citrate buffer into the femoral vein was performed under pentobarbital anesthesia (30.0 mg kg-1, i. p.) in adult Wistar rats fasted for 72 hours. Rats with plasma glucose concentrations of 20.0 mmol L-1 or greater in addition to polyuria, hyperphagia and decrease of body weight were considered as diabetic. All studies were carried out 2 weeks after the injection of STZ. Non-insulin dependent diabetes mellitus (NIDDM) rats were induced according to the previous method [9] by which fasted Wistar rats were intra-peritoneally administered with 200 mg nicotinamide (Sigma, St. Louis, MO, USA) per kg of body weight. Fifteen minutes later, animals under light ether anesthesia were administered with 60 mg streptozotocin (Sigma Chemical Co.) per kg of body weight via tail vein injection to induce diabetes. The plasma glucose concentrations of these NIDDM rats were within 9.0 - 11.0 mmol L-1. All studies were performed 4 weeks after the injection of STZ.
#Determination of plasma glucose
Blood samples (0.2 mL) were collected with a chilled syringe containing 10 IU heparin (Sigma; St. Louis, MO, USA) from the tail vein of rats under anesthesia with sodium pentobarbital (30.0 mg/kg, i. p.). Blood samples were then centrifuged at 13 000 rpm for 3 min, and an aliquot (10 μL) of plasma was added to 1.0 mL of Glucose Kit Reagent (Biosystems S.A.; Barcelona, Spain) and incubated at 37 °C in a water bath (Yamato-BT-25; Tokyo, Japan) for 5 min. The concentration of plasma glucose was then estimated via an analyzer (Biosystems 330; Barcelona, Spain) with samples run in duplicate.
#Measurement of serum insulin concentrations
Determination of the serum insulin concentration was performed by using an adopted ELISA (Rat Insulin ELISA; Mercodia AB; Uppsala, Sweden) [10].
#Intravenous glucose tolerance test (IVGTT)
An intravenous glucose tolerance test (IVGTT) was performed according to the method described previously [3]. Briefly, the basal plasma glucose concentration was obtained from samples taken from the femoral vein of Wistar rats under anesthesia with sodium pentobarbital (30.0 mg/kg, i. p.) before the IVGTT. A solution of thaliporphine at 1.0 mg/kg or the same volume of saline was injected into the femoral vein of rats. After 30 min, blood samples (0.2 mL) from the femoral vein were drawn and indicated as 0 min. Then, a glucose dose of 1.0 g/kg was injected through the femoral vein of rats. Rats receiving a similar injection of saline at the same volume were taken as control. Blood samples (0.2 mL) from the tail vein were drawn at 10, 20, 30, 60, 90, and 120 min following the glucose injection for the measurement of the plasma glucose concentrations. Rats were maintained under anesthesia by pentobarbital throughout the procedure.
#Glycogen assay
About 50 mg of muscle sample was dissolved in 1 N KOH at 70 °C for 30 min. The dissolved homogenate was neutralized by glacial acetic acid and incubated overnight in acetate buffer (0.3 M sodium acetate, pH 4.8) containing amyloglucosidase (Sigma). Samples were then analyzed by measuring glucosyl units using the Trinder reaction. The reaction mixture was neutralized with 1 N NaOH [13].
#Statistical analysis
Results of plasma glucose lowering activity were calculated as percentage decrease of the initial value according to formula: (Gi - Gt)/Gi × 100 %, where Gi was the initial glucose concentration and Gt was the plasma glucose concentration after treatment with test agents. Data are represented as the mean ± sem for the number (n) of animals in the group as indicated in the figures. The results from the experiments are shown as mean ± SEM. Statistical analysis was performed by one-way analysis of variance (ANOVA) with Dunnett’s post-hoc test. P < 0.05 was regarded as statistically significant.
#Results and Discussions
We found that intravenous injection of aporphines and aporphine derivatives (Fig. [1]) could lower the plasma glucose concentration in the normal and diabetic rats with different activities. Thaliporphine significantly decreased the blood glucose at doses ranging from 0.1 to 1.0 mg/kg in normal rats (Fig. [2]), NA-STZ-diabetic rats (Fig. [3]), and STZ-diabetic rats (Fig. [4]). However, higher doses were required to lower the plasma glucose in normal and NA-STZ-diabetic rat by N-[2-(2-methoxyphenoxy)ethyl]norglaucine [more than 5.0 mg/kg (Figs. [2] and [3])] and by diacetyl-N-allylsecoboldine [more than 3.0 mg/kg (Figs. [2] and [3])]. In STZ-diabetic rats, the plasma glucose lowering activities of N-[2-(2-methoxyphenoxy)ethyl]norglaucine and diacetyl-N-allylsecoboldine were found at doses higher than 7.0 mg/kg and 5.0 mg/kg, respectively. Thaliporphine had a more potent plasma glucose lowering activity than N-[2-(2-methoxyphenoxy)ethyl]norglaucine and diacetyl-N-allylsecoboldine in either normal or diabetic rats. The plasma glucose lowering activities of thaliporphine and other aporphines, including boldine, and glaucine, N-methyllaurotetanine and predicentrine, were compared with the effect of insulin (0.5 IU/kg, i. p.) in normal, NA-STZ-diabetic, and STZ-diabetic rats as shown in Fig. [5]. Insulin (0.5 IU/kg, i. p.) decreased the plasma glucose by 24.1 ± 0.5 % in normal rats, 20.5 ± 3.4 % in NA-STZ-diabetic rats, and 16.9 ± 0.9 % in STZ-diabetic rats. At the loading dose of 0.3 mg/kg, the order of the averaged plasma glucose lowering activities were thaliporphine (normal 19.1 ± 2.2 %, NIDDM 19.1 ± 3.5 %), glaucine (normal 16.5 ± 2.5 %, NIDDM 17.2 ± 3.1 %), boldine (normal 14.6 ± 2.6 %, NIDDM 11.6 ± 3.6 %), predicentrine (normal 14.0 ± 2.3 %, NIDDM 8.7 ± 3.2 %) and N-methyllaurotetanine (normal 5.5 ± 2.2 %, NIDDM 3.9 ± 1.5 %) in normal rats and NA-STZ-diabetic rats. However, in STZ-diabetic rats, the order of the averaged plasma glucose lowering activities was found to be N-methyllaurotetanine (14.1 ± 2.5 % decrease), predicentrine (11.1 ± 2.8 % decrease), thaliporphine (11.7 ± 2.5 % decrease), glaucine (4.7 ± 2.5 % decrease) and boldine (3.6 ± 2.1 % decrease). Blood insulin levels in normal and NIDDM rats were significantly increased by thaliporphine from 7.7 ± 2.2 to 14.9 ± 2.3 μIU mL-1 and 6.4 ± 2.3 to 15.2 ± 3.3 μIU mL-1, respectively (n = 8, P < 0.05) (Table [1]). The alteration of plasma insulin levels associated with the plasma glucose lowering effect of aporphine derivatives was mainly examined in NA-STZ-diabetic rats and compared with glibenclamide (1.0 mg/kg, i. v.), which is known as an insulin secretagogue [11], [12]. At 1.0 mg/kg, thaliporphine, boldine and glaucine increased plasma insulin to a level comparable to that induced by glibenclamide (Table [2]). N-[2-(2-Methoxyphenoxy)ethyl]norglaucine and diacetyl-N-allylsecoboldine, which have less potent hypoglycemic activities than thaliporphine, have to be administered at higher doses (7.0 mg/kg and 5.0 mg/kg each) to induce a comparable increase of plasma insulin level (Table [3]) and a comparable decrease of plasma glucose level (Fig. [3]) in NA-STZ-diabetic rats. In STZ-diabetic rats, thaliporphine did not alter the insulin level (Table [1]) but significantly decreased the plasma glucose level (Fig. [4]). Table [4] shows that thaliporphine could increase glycogen synthesis of the soleus skeletal muscle in either normal or diabetic rats. The effect of thaliporphine on glucose utilization was further verified with the IVGTT test, which shows that thaliporphine markedly accelerated the glucose uptake and utilization into peripheral tissues 60 - 90 min after i. v. infusion with glucose (Fig. [6]). The result indicates that thaliporphine exerts an antihyperglycemic action through insulin-dependent and insulin-independent mechanisms. Since boldine and glaucine exerted less potent hypoglycemic action in STZ-diabetic rats, both compounds may lower the plasma glucose mainly through an insulin-dependent mechanism in NA-STZ-diabetic rats. In contrast, N-methyllaurotetanine and predicentrine produce their antihyperglycemic effect through an insulin-independent mechanism. Especially, N-methyllaurotetanine markedly decreased the plasma glucose in STZ-diabetic rats, but did not affect the plasma glucose in normal and NA-STZ-diabetic rats. The detailed mechanisms for the differences in the antihyperglycemic activities among these aporphine and thaliporphine derivatives remain to be determined.
Fig. 2 The relationship of the dose and hypoglycemic activity of aporphine derivatives in normal rats. Data are mean ± SEM (n = 8). Asterisks indicate significant difference as compared with the basal plasma glucose before drug-treatment (* P < 0.05, ** P < 0.01 by one-way ANOVA with Dunnett’s post-hoc test). Glibenclamide used as positive control. Glibenclamide (1.0 mg kg-1) lowered the plasma glucose from 119.3 ± 5.8 mg dL-1 to 82.6 6 2 mg dL-1 in normal rats (n = 8, P < 0.01).
Fig. 3 The relationship between dose and hypoglycemic activity of aporphine derivatives in NA-STZ-diabetic rats. Data are mean ± SEM (n = 8). Asterisks indicate significant difference as compared with the basal plasma glucose before drug-treatment (* P < 0.05, ** P < 0.01 by one-way ANOVA with Dunnett’s post-hoc test). Glibenclamide used as positive control. Glibenclamide (1.0 mg kg-1) lowered the plasma glucose from 157.0 ± 4.4 mg dL-1 to 111.0 ± 6.4 mg dL-1 in NA-STZ-diabetic rats (n = 8, P < 0.05).
Fig. 4 The relationship between dose and hypoglycemic activity of aporphine derivatives in STZ-diabetic rats. Data are mean ± SEM (n = 8). Asterisks indicate significant difference as compared with the basal plasma glucose before drug-treatment (* P < 0.05, ** P < 0.01 by one-way ANOVA with Dunnett’s post-hoc test). Insulin (0.5 IU/kg, i. p.) lowered the plasma glucose from 467.8 ± 5.8 mg dL-1 to 388.0 ± 6.2 mg dL-1 (n = 8, P < 0.05) used as positive control.
Fig. 5 Comparison of the plasma glucose lowering activity of thaliporphine derivatives at doses of 0.3 mg/kg (i. v.) in (A) normal rats, (B) NA-STZ-diabetic rats, and (C) STZ-diabetic rats. Values of mean ± S.E.M. were obtained from eight animals in each group. Asterisks indicate significant difference in plasma glucose lowering activity between vehicle and drug-treatment groups (n = 8, p < 0.05, by one-way ANOVA with Dunnett"s post-hoc test). Insulin (0.5 IU/kg, i. v.) was used as positive control and lowered the plasma glucose by 24.1 ± 0.5 % (n = 8) in normal rats, by 20.5 ± 3.4 % (n = 8) in NA-STZ-diabetic rats, and by 16.9 ± 0.9 % (n = 8) in STZ-diabetic rats. Glibenclamide (0.3 mg kg-1, i. v.) was used as positive control and lowered the plasma glucose by 24.1 ± 4.6 % (n = 8) in normal rats, by 19.1 ± 1.8 % (n = 8) in NA-STZ-diabetic rats, and by 1.2 ± 1.4 % (n = 8) in STZ-diabetic rats.
Fig. 6 Effect of thaliporphine on plasma glucose in Wistar normal rats receiving an intravenous glucose tolerance test (IVGTT). IVGTT was performed by injection of glucose at 1 g kg-1 into two groups of normal rats 5 min after intravenous injection with thaliporphine (1 mg kg-1, open circles) or vehicle (solid circles) through the femoral vein. The blood samples were obtained at the indicated time points before (0 min) and after i. v. glucose. Asterisks indicate the significant difference in plasma glucose between vehicle- and thaliporphine-treated groups checked at the same time point (* P < 0.05, n = 8, by one-way ANOVA with Dunnett’s post-hoc test).
| Groups | Plasma insulin (μIU mL-1) | |
| Pre-treatment | Post-treatment | |
| Normal rats | ||
| Vehicle | 7.6 ± 1.3 | 8.2 ± 1.5 |
| Thaliporphine (1.0 mg kg-1) | 7.7 ± 2.2 | 14.9 ± 2.3* |
| Glibenclamide (1.0 mg kg-1) | 8.4 ± 2.5 | 20.2 ± 2.0* |
| NA-STZ rats (NIDDM) | ||
| Vehicle | 6.8 ± 2.3 | 7.2 ± 2.5 |
| Thaliporphine (1.0 mg kg-1) | 6.4 ± 2.3 | 15.2 ± 3.3* |
| Glibenclamide (1.0 mg kg-1) | 6.7 ± 2.0 | 19.2 ± 2.7* |
| STZ rats (IDDM) | ||
| Vehicle | 3.2 ± 0.3 | 3.1 ± 0.5 |
| Thaliporphine (1.0 mg kg-1) | 2.9 ± 1.4 | 3.3 ± 0.6 |
| Glibenclamide (1.0 mg kg-1) | 3.7 ± 0.3 | 4.2 ± 1.2 |
| Values expressed as mean ± S.E.mean from eight animals in each group. | ||
| * P < 0.05 vs. animals treated with vehicle only. | ||
| Groups | Plasma insulin (μIU mL-1) | |
| Pre-treatment | post-treatment | |
| NA-STZ rats (NIDDM) | ||
| Vehicle | 6.8 ± 2.3 | 7.2 ± 2.5 |
| Thaliporphine (1.0 mg kg-1) | 6.4 ± 2.3 | 15.2 ± 3.3* |
| Boldine (1.0 mg kg-1) | 6.4 ± 0.5 | 15.1 ± 2.0* |
| N-Methyllaurotetanine (1.0 mg kg-1) | 7.2 ± 2.4 | 9.5 ± 1.6 |
| Predicentrine (1.0 mg kg-1) | 6.6 ± 2.3 | 10.4 ± 1.8 |
| Glaucine (1.0 mg kg-1) | 6.2 ± 2.6 | 14.6 ± 2.3* |
| Glibenclamide (1.0 mg kg-1) | 6.7 ± 2.0 | 17.8 ± 2.7* |
| Values expressed as mean ± S.E.mean from eight animals in each group. | ||
| * P < 0.05 vs. animal treated with vehicle only. | ||
| Groups | Plasma insulin (μIU mL-1) | |
| Pre-treatment | Post-treatment | |
| NA-STZ rats (NIDDM) | ||
| Vehicle | 6.8 ± 2.3 | 7.2 ± 2.5 |
| Thaliporphine (1.0 mg kg-1) | 6.4 ± 2.3 | 15.2 ± 3.3* |
| N-[2-(2-Methoxyphenoxy)ethyl]norglucine (7.0 mg kg-1) | 7.1 ± 2.2 | 15.8 ± 2.2* |
| Diacetyl-N-allylsecoboldine (5.0 mg kg-1) | 6.3 ± 1.8 | 16.3 ± 2.5* |
| Glibenclamide (1.0 mg kg-1) | 6.3 ± 2.0 | 18.9 ± 2.7* |
| Values expressed as mean ± S.E. mean from eight animals in each group. | ||
| *P < 0.05 vs. animal treated with vehicle only. | ||
| Group | Glycogen synthesis (μmol/g wet weight ) |
| Normal | |
| Vehicle | 49.3 ± 2.9 |
| Thaliporphine | 59.6 ± 3.2* |
| Insulin | 71.0 ± 3.2* |
| NA-STZ rats (NIDDM) | |
| Vehicle | 45.2 ± 3.5 |
| Thaliporphine | 60.5 ± 3.6* |
| Insulin | 77.9 ± 1.9* |
| STZ-diabetic rats | |
| Vehicle | 30.1 ± 2.3 |
| Thaliporphine | 65.6 ± 3.3* |
| Insulin | 72.7 ± 5.5* |
| Values expressed as mean ± S.E.mean from six animals in each group. | |
| * P < 0.05 vs. control animal treated with vehicle only. | |
Acknowledgements
The present study was supported in part by a grant from the Technology Development Program for Academia (92-EC-17-A-20-S1 - 0010 ).
#References
- 1 Lopez-Candales A. Metabolic syndrome X: a comprehensive review of the pathophysiology and recommended therapy. J Med. 2001; 32 283-300
- 2 Rao N SK, Lee S S. Preparation of thaliporphine and liioferine from glaucine by treatment with hydrogen bromide. J Clin Chem Soc. 2000; 47 227-30
- 3 Lee S S, Lin Y J, Chen M Z, Wu Y C, Chen C H. A facile semisynthesis of litebamine, a novel phenanthrene alkaloid, from boldine via a biogenetical approach. Tetrahedron Lett. 1992; 33 6309-10
- 4 Guinaudeau H, Leboenf L M, Cave A. Aporphine alkaloids. J Nat Prod. 1975; 38 275
- 5 Huang W J, Chen C H, Singh O V, Lee S L, Lee S S. A facile method for the synthesis of glaucine and norglaucine from boldine. Synth Commun. 2002; 32 3681-6
- 6 Hung L M, Lee S S, Chen J K, Huang S S, Su M J. Thaliporphine protects ischemic and ischemic-reperfused rat hearts via an NO-dependent mechanism. Drug Dev Res. 2001; 52 446-53
- 7 Su M J, Chang Y M, Chi J F, Lee S S. Thaliporphine, a positive inotropic agent with a negative chronotropic action. Eur J Pharmacol. 1994; 254 141-50
- 8 Forman L J, Estilow S, Mead J, Vasilenko P. Eight weeks of streptozotocin-induced diabetes induces the effects of cold stress on immunoreactive beta-endorphin levels in female rats. Horm Metab Res. 1988; 20 555-8
- 9 Masiello P, Broca C, Gross R, Roye M, Manteghetti M, Hillaire-Buye D. et al . Development of a new model in adult rats administered streptozotocin and nicotinamide. Diabetes. 1998; 47 224-9
- 10 Jansson L, Carlsson P O, Bodin B, Andersson A, Kallskog O. Neuronal nitric oxide synthase and splanchnic blood flow in anaesthetized rats. Acta Physiol Scand. 2005; 183 257-62
- 11 Pratz J, Mondot S, Montier F, Cavero I. Effect of K+ channel activators, RP52891, cromakalim and diazoxide, on the plasma insulin level, plasma rennin activity and blood pressure in rats. J Pharmacol Exp Ther. 1991; 21 216-22
- 12 Garrel D R, Picq R, Bajard L, Harfouche M, Tourniaire J. Acute effect of glyburide on insulin sensitivity in type I diabetic patients. J Clin Endocrinol Metab. 1987; 65 896-900
- 13 Chou C H, Tsai Y L, Hou C W, Lee H H, Chang W H, Lin T W. et al . Glycogen overload by postexercise insulin administration abolished the exercise-induced increase in GLUT4 protein. J Biomed Sci. 2005; 12 991-8
- 14 Yu B C, Hung C R, Chen W C, Cheng J T. Antihyperglycemic effect of andrographolide in streptozotocin-induced diabetic rats. Planta Med. 2003; 69 1075-9
M. J. Su, Ph. D.
Institute of Pharmacology
College of Medicine
National Taiwan University
No. K1, Sec. 1, Jen-Ai Rd
Taipei
Taiwan
Republic of China
Phone: +886-2-2312-3456 ext. 8317
Fax: +886-2-2397-1403
Email: mjsu@ha.mc.ntu.edu.tw
References
- 1 Lopez-Candales A. Metabolic syndrome X: a comprehensive review of the pathophysiology and recommended therapy. J Med. 2001; 32 283-300
- 2 Rao N SK, Lee S S. Preparation of thaliporphine and liioferine from glaucine by treatment with hydrogen bromide. J Clin Chem Soc. 2000; 47 227-30
- 3 Lee S S, Lin Y J, Chen M Z, Wu Y C, Chen C H. A facile semisynthesis of litebamine, a novel phenanthrene alkaloid, from boldine via a biogenetical approach. Tetrahedron Lett. 1992; 33 6309-10
- 4 Guinaudeau H, Leboenf L M, Cave A. Aporphine alkaloids. J Nat Prod. 1975; 38 275
- 5 Huang W J, Chen C H, Singh O V, Lee S L, Lee S S. A facile method for the synthesis of glaucine and norglaucine from boldine. Synth Commun. 2002; 32 3681-6
- 6 Hung L M, Lee S S, Chen J K, Huang S S, Su M J. Thaliporphine protects ischemic and ischemic-reperfused rat hearts via an NO-dependent mechanism. Drug Dev Res. 2001; 52 446-53
- 7 Su M J, Chang Y M, Chi J F, Lee S S. Thaliporphine, a positive inotropic agent with a negative chronotropic action. Eur J Pharmacol. 1994; 254 141-50
- 8 Forman L J, Estilow S, Mead J, Vasilenko P. Eight weeks of streptozotocin-induced diabetes induces the effects of cold stress on immunoreactive beta-endorphin levels in female rats. Horm Metab Res. 1988; 20 555-8
- 9 Masiello P, Broca C, Gross R, Roye M, Manteghetti M, Hillaire-Buye D. et al . Development of a new model in adult rats administered streptozotocin and nicotinamide. Diabetes. 1998; 47 224-9
- 10 Jansson L, Carlsson P O, Bodin B, Andersson A, Kallskog O. Neuronal nitric oxide synthase and splanchnic blood flow in anaesthetized rats. Acta Physiol Scand. 2005; 183 257-62
- 11 Pratz J, Mondot S, Montier F, Cavero I. Effect of K+ channel activators, RP52891, cromakalim and diazoxide, on the plasma insulin level, plasma rennin activity and blood pressure in rats. J Pharmacol Exp Ther. 1991; 21 216-22
- 12 Garrel D R, Picq R, Bajard L, Harfouche M, Tourniaire J. Acute effect of glyburide on insulin sensitivity in type I diabetic patients. J Clin Endocrinol Metab. 1987; 65 896-900
- 13 Chou C H, Tsai Y L, Hou C W, Lee H H, Chang W H, Lin T W. et al . Glycogen overload by postexercise insulin administration abolished the exercise-induced increase in GLUT4 protein. J Biomed Sci. 2005; 12 991-8
- 14 Yu B C, Hung C R, Chen W C, Cheng J T. Antihyperglycemic effect of andrographolide in streptozotocin-induced diabetic rats. Planta Med. 2003; 69 1075-9
M. J. Su, Ph. D.
Institute of Pharmacology
College of Medicine
National Taiwan University
No. K1, Sec. 1, Jen-Ai Rd
Taipei
Taiwan
Republic of China
Phone: +886-2-2312-3456 ext. 8317
Fax: +886-2-2397-1403
Email: mjsu@ha.mc.ntu.edu.tw
Fig. 1 The chemical structures of aporphines and aporphine derivatives in the present study.
Fig. 2 The relationship of the dose and hypoglycemic activity of aporphine derivatives in normal rats. Data are mean ± SEM (n = 8). Asterisks indicate significant difference as compared with the basal plasma glucose before drug-treatment (* P < 0.05, ** P < 0.01 by one-way ANOVA with Dunnett’s post-hoc test). Glibenclamide used as positive control. Glibenclamide (1.0 mg kg-1) lowered the plasma glucose from 119.3 ± 5.8 mg dL-1 to 82.6 6 2 mg dL-1 in normal rats (n = 8, P < 0.01).
Fig. 3 The relationship between dose and hypoglycemic activity of aporphine derivatives in NA-STZ-diabetic rats. Data are mean ± SEM (n = 8). Asterisks indicate significant difference as compared with the basal plasma glucose before drug-treatment (* P < 0.05, ** P < 0.01 by one-way ANOVA with Dunnett’s post-hoc test). Glibenclamide used as positive control. Glibenclamide (1.0 mg kg-1) lowered the plasma glucose from 157.0 ± 4.4 mg dL-1 to 111.0 ± 6.4 mg dL-1 in NA-STZ-diabetic rats (n = 8, P < 0.05).
Fig. 4 The relationship between dose and hypoglycemic activity of aporphine derivatives in STZ-diabetic rats. Data are mean ± SEM (n = 8). Asterisks indicate significant difference as compared with the basal plasma glucose before drug-treatment (* P < 0.05, ** P < 0.01 by one-way ANOVA with Dunnett’s post-hoc test). Insulin (0.5 IU/kg, i. p.) lowered the plasma glucose from 467.8 ± 5.8 mg dL-1 to 388.0 ± 6.2 mg dL-1 (n = 8, P < 0.05) used as positive control.
Fig. 5 Comparison of the plasma glucose lowering activity of thaliporphine derivatives at doses of 0.3 mg/kg (i. v.) in (A) normal rats, (B) NA-STZ-diabetic rats, and (C) STZ-diabetic rats. Values of mean ± S.E.M. were obtained from eight animals in each group. Asterisks indicate significant difference in plasma glucose lowering activity between vehicle and drug-treatment groups (n = 8, p < 0.05, by one-way ANOVA with Dunnett"s post-hoc test). Insulin (0.5 IU/kg, i. v.) was used as positive control and lowered the plasma glucose by 24.1 ± 0.5 % (n = 8) in normal rats, by 20.5 ± 3.4 % (n = 8) in NA-STZ-diabetic rats, and by 16.9 ± 0.9 % (n = 8) in STZ-diabetic rats. Glibenclamide (0.3 mg kg-1, i. v.) was used as positive control and lowered the plasma glucose by 24.1 ± 4.6 % (n = 8) in normal rats, by 19.1 ± 1.8 % (n = 8) in NA-STZ-diabetic rats, and by 1.2 ± 1.4 % (n = 8) in STZ-diabetic rats.
Fig. 6 Effect of thaliporphine on plasma glucose in Wistar normal rats receiving an intravenous glucose tolerance test (IVGTT). IVGTT was performed by injection of glucose at 1 g kg-1 into two groups of normal rats 5 min after intravenous injection with thaliporphine (1 mg kg-1, open circles) or vehicle (solid circles) through the femoral vein. The blood samples were obtained at the indicated time points before (0 min) and after i. v. glucose. Asterisks indicate the significant difference in plasma glucose between vehicle- and thaliporphine-treated groups checked at the same time point (* P < 0.05, n = 8, by one-way ANOVA with Dunnett’s post-hoc test).