OBJECTIVETo observe the effects of (-)doxazosin(DOX), (+)DOX and (+/-)DOX on serum lipid levels and the mortality rates of the rabbits fed by an atherogenic diet.

METHODSMale white New Zealand rabbits were fed by an atherogenic diet for 4 weeks. 8 rabbits whose serum TC <10 mmol/L were confirmed as normal diet group and were fed normally. 40 rabbits whose serum TC >10 mmol/L were randomly divided into 4 groups (n=10): atherogenic diet group, atherogenic diet with (-)DOX group, atherogenic diet with (+)DOX group and atherogenic diet with (+/-)DOX group, which were intraperitoneally injected with (-)DOX, (+)DOX and (+/-)DOX for 9 weeks respectively. Normal and atherogenic diet group were intraperitoneally injected with double distilled water. After 9 weeks administration of (+/-)doxazosin and its enantiomers, effects of the three agents on serum levels of total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C) were observed.

RESULTSThe mortality rate of the rabbits fed by an atherogenic diet for 13 weeks was 40%, and it was much higher than that of the rabbits fed by a normal diet (10%). The mortality rates in the rabbits treated with (-)DOX and (+/-)DOX were lower than that in the rabbits fed by a normal diet (10%). Serum LDL-C level of the rabbits was increased markedly after 4 weeks of atherogenic diet, and it was further increased significantly (P < 0.05 and P < 0.01) during the continued 9 weeks of atherogenic diet. However, serum LDL-C levels were not further increased significantly (P > 0.05) during the continued 9 weeks of atherogenic diet in the rabbits treated with (-)DOX, (+)DOX and (+/-)DOX, respectively.

CONCLUSION(-)DOX and (+/-)DOX increase the survival rate and improve LDL-C disorder mildly in the rabbits fed by an atherogenic diet. The improvements in LDL-C induced by (-)DOX and (+/-)DOX, however, might not be the reason for exploration about the increased survival rate in the rabbits fed by an atherogenic diet.

Animals ; Cholesterol, Dietary ; administration & dosage ; Diet, Atherogenic ; Doxazosin ; pharmacology ; Hyperlipidemias ; blood ; drug therapy ; etiology ; Lipids ; blood ; Male ; Rabbits ; Stereoisomerism

Alpha1a-adrenergic receptor (AR) primarily mediates the contraction of the prostatic and cavernous smooth muscles. Among clinically available alpha1-AR antagonists for the medical management of benign prostatic hyperplasia (BPH), tamsulosin has a modest selectivity for alpha1A- and alpha1D- over alpha1B-ARs. To compare the effects of various alpha1-AR antagonists on relaxation responses of cavernous and trigonal smooth muscles, isometric tension studies with relatively selective (tamsulosin) and non-selective (prazosin, doxazosin, and terazosin) alpha1A-AR antagonists, were conducted in the cavernous and trigonal muscle strips of rabbits (n=10 each). Tamsulosin had the strongest inhibitory effect on contraction of trigonal smooth muscle among the various alpha1-AR antagonists, and the inhibitory activities of prazosin, doxazosin, and terazosin were not statistically different. All alpha1-AR antagonists caused concentration-dependent relaxation of the cavernous muscle strips. Tamsulosin was shown to have greater potency than prazosin (more than 100-fold), doxazosin (more than 1000-fold), and terazosin (more than 1000-fold), in relaxation of cavernous smooth muscle. In conclusion, tamsulosin might be the most effective drug among the four commonly used alpha1-AR antagonists for the medical management of BPH. Tamsulosin might be a potential substitute for phentolamine in combination with vasoactive agents as an intracavernous injection therapy for patients with erectile dysfunction.
Adrenergic alpha-Antagonists/pharmacology* ; Animal ; Comparative Study ; Doxazosin/pharmacology* ; In Vitro ; Muscle Contraction/drug effects ; Muscle Relaxation/drug effects* ; Muscle, Smooth/physiology ; Muscle, Smooth/drug effects* ; Prazosin/pharmacology* ; Rabbits ; Receptors, Adrenergic, alpha-1/antagonists & inhibitors* ; Sulfonamides/pharmacology*

BACKGROUND/AIMS: The development of therapeutic strategies for the treatment of cirrhosis has become an important focus for basic and clinical researchers. Adrenergic receptor antagonists have been evaluated as antifibrotic drugs in rodent models of carbon tetrachloride (CCl4)-induced cirrhosis. The aim of the present study was to evaluate the effects of carvedilol and doxazosin on fibrosis/cirrhosis in a hamster animal model. METHODS: Cirrhotic-induced hamsters were treated by daily administration of carvedilol and doxazosin for 6 weeks. Hepatic function and histological evaluation were conducted by measuring biochemical markers, including total bilirubin, aspartate aminotransferase, alanine aminotransferase and albumin, and liver tissue slices. Additionally, transforming growth factor beta (TGF-beta) immunohistochemistry was analyzed. RESULTS: Biochemical markers revealed that hepatic function was restored after treatment with doxazosin and carvedilol. Histological evaluation showed a decrease in collagen type I deposits and TGF-beta-secreting cells. CONCLUSIONS: Taken together, these results suggest that the decrease in collagen type I following treatment with doxazosin or carvedilol is achieved by decreasing the profibrotic activities of TGF-beta via the blockage of alpha1- and beta-adrenergic receptor. Consequently, a diminution of fibrotic tissue in the CCl4-induced model of cirrhosis is achieved.
Adrenergic alpha-1 Receptor Antagonists/*pharmacology ; Alanine Transaminase/blood ; Animals ; Aspartate Aminotransferases/blood ; Bilirubin/blood ; Carbazoles/*pharmacology ; Carbon Tetrachloride ; Collagen Type I/drug effects/metabolism ; Cricetinae ; Doxazosin/*pharmacology ; Liver/metabolism/pathology ; Liver Cirrhosis/blood/chemically induced/*drug therapy ; Liver Function Tests ; Propanolamines/*pharmacology ; Serum Albumin/analysis ; Transforming Growth Factor beta/blood/*drug effects

Doxazosin, a high selective alpha1-adrenoceptor antagonist, is considered as the first-line therapy for the patients with benign prostatic hyperplasia (BPH) and also produce several side effects in cardiovascular system. In this study, we observed the isometric vasoconstrictive responses of the rabbit isolated arterial rings to electric field stimulation and noradrenaline ( NA ) to study the effects of R-doxazosin ( R-DOX ) and S-doxazosin ( S-DOX ) on the alpha1-adrenoceptor-regulated vasoconstrictive responses in the rabbit isolated ear artery, mesenteric artery and pulmonary artery, and the effects of higher concentration of S-DOX and R-DOX on presynaptic alpha2-adrenoceptor-regulated purinergic vasoconstriction in the rabbit isolated saphenous artery. We found that R-DOX and S-DOX competitively inhibited the vasoconstriction induced by NA in the rabbit isolated ear artery, mesenteric artery and pulmonary artery. The pA2 values of R-DOX and S-DOX against NA in the rabbit isolated ear artery, mesenteric artery and pulmonary artery were 7. 91 +/- 0. 03 and 7. 53 +/- 0. 05, 7. 80 +/- 0. 05 and 7. 29 +/-0. 07, 8. 32 +/- 0. 06 and 7. 97 +/- 0. 07, respectively. The pA2 values of R-DOX in the three arterial preparations were significantly higher than those of S-DOX (P < 0. 01). R-DOX and S-DOX at the concentrations of 0. 1 - 10 micromol x L (-1) did not affect the vasoconstriction induced by electric stimulation in the rabbit isolated saphenous artery. R-DOX and S-DOX at 100 micromol x L(-1) in the rabbit isolated saphenous artery completely inhibited the vascular responses to exogenous NA, but did not affect the vascular responses to exogenous adenosine triphosphate (1 mmol x L(-1) ). It is reasonable to suggest that R-DOX and S-DOX competitively inhibit the vasoconstriction induced by NA in the rabbit ear artery, mesenteric artery and pulmonary artery, and the pA2 values of S-DOX are significantly lower than those of R-DOX. The higher concentration (10 micromol x L(-1)) of R-DOX and S-DOX does not affect the presynaptic alpha2-adrenoceptors at sympathetic nerve terminals of the rabbit saphenous artery.
Adrenergic alpha-2 Receptor Antagonists ; Adrenergic alpha-Antagonists ; chemistry ; pharmacology ; Animals ; Blood Vessels ; drug effects ; physiology ; Dose-Response Relationship, Drug ; Doxazosin ; chemistry ; pharmacology ; Electric Stimulation ; In Vitro Techniques ; Male ; Mesenteric Arteries ; drug effects ; physiology ; Norepinephrine ; pharmacology ; Pulmonary Artery ; drug effects ; physiology ; Rabbits ; Receptors, Adrenergic, alpha-2 ; physiology ; Stereoisomerism ; Vasoconstriction ; drug effects