Abstract
In this work, the potential vasorelaxant activity of (+)-nantenine, an alkaloid isolated from Platycapnos spicata, was studied for the first time in rat aorta. (+)-Nantenine (3 - 30 μM) totally relaxed, in a concentration-dependent manner and with almost equal effectiveness, the contractions induced by noradrenaline (NA) or by a high KCl concentration (60 mM) in intact rat aortic rings. Mechanical removal of endothelium and/or pretreatment of aorta rings with glibenclamide (10 μM) or tetraethylammonium (TEA, 2 mM) did not significantly modify the vasorelaxant effects of this aporphine alkaloid. In the experiments in Ca2+-free medium, (+)-nantenine (10 μM) had no effect on caffeine-induced contractions. Furthermore, in the studies with radiolabelled Ca2+, (+)-nantenine (3 - 30 μM) did not modify the basal uptake of 45Ca2+ but decreased, in a concentration-dependent fashion, the influx of 45Ca2+ induced by NA and KCl in endothelium-containing and endothelium-denuded rat aortic rings. In addition, (+)-nantenine (3 - 30 μM) was ineffective to scavenge superoxide anion (O2
-) radicals generated by the hypoxanthine (HX)-xanthine oxidase (XO) system and/or to inhibit XO activity. These results indicate that: a) the vasorelaxant effects of (+)-nantenine in rat aorta are due, at least in part, to a blockage of Ca2+ influx through transmembrane calcium channels, b) the activation of ATP-sensitive K+ channels (KATP) and large conductance Ca2+-activated K+ channels (KCa) present in smooth muscle cells, the presence (integrity) of endothelial system, an inhibitory action on XO enzymatic activity and/or O2
- radicals scavenging properties are not involved in the vascular effects of (+)-nantenine in rat aorta described above.
Abbreviations
HX:hypoxanthine
IP3:inositol 1,4,5-trisphosphate
KATP:ATP-sensitive K+ channels
KCa:large conductance Ca2+-activated K+ channels
NBT:nitro blue tetrazolium
NA:noradrenaline
NO:nitric oxide
OD:optical density
O2
·-:superoxide anion
SOD:superoxide dismutase
TEA:tetraethylammonium
XO:xanthine oxidase
Key words
Vasorelaxant effects - rat aorta rings - calcium antagonist activity - (+)-nantenine - superoxide anions - xantine oxidase activity
References
-
1
Takase T, Ohashi H.
Action of domesticine methyl ether upon peripheral nerves.
Journal of Pharmacological Society of Japan.
1927;
541
210-4
-
2
Nakai N, Fujii Y, Kobashi K, Nomura K.
Aldose reductase inhibitors: flavonoids, alkaloids, acetophenones, benzophenones and spirohydantoins of chroman.
Archives of Biochemistry and Biophysics.
1985;
239
491-6
-
3
Philipov S, Ivanovska N, Istatkova R, Velikova M, Tuleva P.
Phytochemical study and cytotoxic activity of alkaloids from Uvaria chamae P. Beauv.
Pharmazie.
2000;
55
688-9
-
4
Shoji N, Umeyama A, Takemoto T, Ohizumi Y.
Serotonergic receptor antagonist from Nandina domestica Thunberg.
Journal of Pharmaceutical Sciences.
1984;
73
568-70
-
5
Guinaudeau H, Leboeuf M, Cave A.
Aporphinoid alkaloids, IV.
Journal of Natural Products.
1988;
51
389-474
-
6 Blanco O, Castedo L, Villaverde M C, Loza M I, Orallo F, Alzueta A F. et al .Isolation of pharmacologically active alkaloids from Platycapnos spicata
. Abstract book of the International Research Congress on Natural Products Chicago; 1991: P-82
-
7
Orallo F.
Study of the in vivo and in vitro cardiovascular effects of a hydralazine-like vasodilator agent (HPS-10) in normotensive rats.
British Journal of Pharmacology.
1997;
121
1627-36
-
8
Holland H L, Gu J -X, Orallo F, Camiña M, Fabeiro P.
Enantioselective synthesis and pharmacological evaluation of a new type of verapamil analog with hypotensive and calcium antagonist activities.
Pharmaceutical Research.
1999;
16
281-7
-
9
Robak J, Gryglewski R J.
Flavonoids are scavengers of superoxide anions.
Biochemical Pharmacology.
1988;
37
837-41
-
10
Orallo F.
Regulation of cytosolic calcium levels in vascular smooth muscle.
Pharmacology and Therapeutics.
1996;
69
153-71
-
11
Muramatsu I, Ohmura T, Kigoshi S, Hashimoto S, Oshita M.
Pharmacological subclassification of α1-adrenoceptors in vascular smooth muscle.
British Journal of Pharmacology.
1990;
99
197-201
-
12
Fagura M S, Lydford S J, Dougall I G.
Pharmacological classification of alpha 1-adrenoceptors mediating contractions of rabbit isolated ear artery: comparison with rat isolated thoracic aorta.
British Journal of Pharmacology.
1997;
120
247-58
-
13 Bylund D B, Bond R A, Clarke D E, Eikenburg D C, Hieble J P, Langer S Z. et al .Adrenoceptors. In: The IUPHAR Compendium of Receptor Characterization and Classification. The IUPHAR Committe on Receptor Nomenclature and Drug Classification, editor IUPHAR Media Ltd. London; 1998: 58-74
-
14
Kuriyama H, Kitamura K, Nabata H.
Pharmacological and physiological significance of ion channels and factors that modulate them in vascular tissues.
Pharmacological Reviews.
1995;
47
387-573
-
15
Vanhoutte P M.
Say NO to ET.
Journal of the Autonomic Nervous System.
2000;
81
271-7
-
16
Furchgott R F.
Endothelium-derived relaxing factor : Discovery, early studies, and identification as nitric oxide.
Bioscience Reports.
1999;
19
235-51
-
17
Ignarro L J, Cirino G, Casini A, Napoli C.
Nitric oxide as a signalling molecule in the vascular system.
Journal of Cardiovascular Pharmacology.
1999;
34
879-86
-
18
Lee C I, Liu X, Zweier J L.
Regulation of xanthine oxidase by nitric oxide and peroxynitrite.
Journal of Biological Chemistry.
2000;
275
9369-76
-
19
Noguera M A, D’Ocon M P.
Different and common intracellular calcium-stores mobilized by noradrenaline and caffeine in vascular smooth muscle.
Naunyn-Schmiedeberg’s Archives of Pharmacology.
1992;
345
333-41
-
20
Quast U.
Do the K+ channel openers relax smooth muscle by opening K+ channels?.
Trends in Pharmacological Sciences.
1993;
14
332-7
Dr. Francisco Orallo
Departamento de Farmacología
Facultad de Farmacia
Universidad de Santiago de Compostela
Campus Universitario Sur
15782 Santiago de Compostela (La Coruña)
Spain
eMail: fforallo@usc.es
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