ABSTRACT
Abstract Background: Labdane-type diterpenes induce lower blood pressure via relaxation of vascular smooth muscle; however, there are no studies describing the effects of labdanes in hypertensive rats. Objective: The present study was designed to investigate the cardiovascular actions of the labdane-type diterpene ent-3-acetoxy-labda-8(17), 13-dien-15-oic acid (labda-15-oic acid) in two-kidney 1 clip (2K-1C) renal hypertension. Methods: Vascular reactivity experiments were performed in aortic rings isolated from 2K-1C and normotensive (2K) male Wistar rats. Nitrate/nitrite (NOx) measurement was performed in aortas by colorimetric assay. Blood pressure measurements were performed in conscious rats. Results: Labda-15-oic acid (0.1-300 µmol/l) and forskolin (0.1 nmol/l - 1 µmol/l) relaxed endothelium-intact and endothelium-denuded aortas from both 2K-1C and 2K rats. Labda-15-oic acid was more effective at inducing relaxation in endothelium-intact aortas from 2K pre-contracted with phenylephrine when compared to the endothelium-denuded ones. Forskolin was more potent than labda-15-oic acid at inducing vascular relaxation in arteries from both 2K and 2K-1C rats. Labda-15-oic acid-induced increase in NOx levels was lower in arteries from 2K-1C rats when compared to 2K rats. Intravenous administration of labda-15-oic acid (0.3-3 mg/kg) or forskolin (0.1-1 mg/kg) induced hypotension in conscious 2K-1C and 2K rats. Conclusion: The present findings show that labda-15-oic acid induces vascular relaxation and hypotension in hypertensive rats.
Resumo Fundamento: Diterpenos do tipo labdano induzem uma queda da pressão arterial por meio do relaxamento do músculo liso vascular; todavia, não há estudos que descrevam os efeitos de labdanos em ratos hipertensos. Objetivo: O presente estudo foi desenvolvido para investigar as ações cardiovasculares do labdano ácido ent-3-acetóxi-labda-8(17),13-dieno-15-óico (labda-15-óico) na hipertensão renal dois rins-1 clipe (2R-1C). Métodos: Foram feitos experimentos de reatividade vascular em anéis aórticos isolados de ratos machos 2R-1C e normotensos (2R). A medição de Nitrato/Nitrito (NOx) foi feita nas aortas por meio de ensaio colorimétrico. As medidas de pressão arterial foram feitas em ratos conscientes. Resultados: O ácido labda-15-óico (0,1 - 300 µmol/l) e a forscolina (0,1 nmol/l - 1 µmol/l) relaxaram as aortas com endotélio intacto e as aortas sem endotélio dos ratos 2R-1C e 2R. O labda-15-óico mostrou-se mais eficaz na indução do relaxamento em aortas com endotélio intacto de 2R pré-contraídas com fenilefrina em comparação àquelas sem endotélio. A forscolina mostrou-se mais potente do que o ácido labda-15-óico na indução do relaxamento vascular nas artérias tanto de ratos 2R-1C quanto de ratos 2R. O aumento dos níveis de NOx induzido pelo ácido labda-15-óico foi menor nas artérias de ratos 2R-1C em comparação a ratos 2R. A administração intravenosa de ácido labda-15-óico (0,3-3 mg/kg) ou forscolina (0,1-1 mg/kg) induziu hipertensão em ratos 2R-1C e 2R conscientes. Conclusão: Os presentes resultados mostram que o labda-15-óico induz relaxamento vascular e hipotensão em ratos hipertensos.
Subject(s)
Animals , Male , Rats , Vasodilator Agents/pharmacology , Blood Pressure/drug effects , Colforsin/pharmacology , Diterpenes/pharmacology , Hypertension, Renovascular/drug therapy , Aorta, Thoracic/drug effects , Phenylephrine/antagonists & inhibitors , Vasoconstrictor Agents/antagonists & inhibitors , Vasodilation/drug effects , Vasodilator Agents/chemistry , Colforsin/chemistry , Rats, Wistar , Disease Models, Animal , Diterpenes/chemistry , Drug Evaluation, Preclinical , Hypertension, Renovascular/physiopathology , Muscle, Smooth, Vascular/drug effects , Nitric Oxide/analysisABSTRACT
Isoxsuprine hydrochloride is a peripheral vasodilator. It is advisable to prepare the drug in sustained release dosage forms to improve patient compliance and to achieve a steady state blood level with minimum side effects. Different hydrophilic and hydrophobia polymers in addition to their combinations were used in different ratios to select the best level of the matrix forming material that provides the most sustaining effect. The effect of different types and concentrations of polymers on the release rate of the drug was investigated. The drug release decreased by increasing the concentration of the polymer in all the studied formulations. Tablet formula containing either 30% [w/w] HPMC 15000 or 30% [w/w] Eudragit RSPM gave the most sustaining effect among the single polymers. The drug release rate from tablets prepared using polymer blends is slower compared to that from those containing single polymers. The slowest drug release was obtained from tablet formulae containing: drug, 10% [w/w] HPMC 15000 and 40% [w/w] Eudragit RSPM and drug, 10% [w/w] Eudragit RSPM and 40% [w/w] Eudragit RLPO. The release of isoxsuprine HCl from matrices prepared using single polymer followed Higuchi 's diffusion model However, zero-order release kinetics was elucidated for the release of isoxsuprine HCl from the investigated polymer blends in phosphate buffer [pH 6.8]