THE EFFECTS OF NANOSILVER ON VASCULAR REACTIVITY AND ENDOTHELIAL FUNCTION ON ISOLATED RABBIT CAROTID ARTERY

ABSTRACT

Nanoparticles (Nano particles) are defined as structures with a diameter less than 100 nm and novel physical and chemical properties that differ sharply from the macro forms. The medical use of nanosilver particles is growing mainly due to their antimicrobial properties. The impact of NSPs on the regulation of vascular tone (vasoconstriction/vasodilation), blood flow distribution, heartbeat, electric mechanisms, etc.; as well as their protective or adverse role in the development and progression of cardiovascular pathologies has not been properly understood. The aim of this present work was to determine the effect of nanosilver on vascular reactivity in isolated rabbit carotid artery. The study involved standard laboratory Organ Bath procedures. Twenty milli/liter organ baths containing PSS, bubbled with 95% O₂, 5% CO₂ and maintained at 37^oC and pH 7.4. The recording system is a 4-channel Grass Polygraph. Cumulative dose response tests to agonists phenylephrine (PE), was examined separately, in normal PSS (control). Contractile responses were analysed with reference to maximal contractions induced by 80 mM K⁺ in normal PSS. In another experiment, arterial rings were precontracted with EC₇₀ M PE and /or high potassium PSS (80 mM K⁺). At stable contraction, cumulative relaxation response to nanosilver was studied. The above protocol was repeated in endothelium intact (+E) (control) and endothelium denuded (-E) rings. In another experiment, arterial rings were precontracted in 20 mM K⁺. At a stable contraction, cumulative relaxation response to nanosilver was studied. Cumulative dose response tests to phenylephrine was examined in normal PSS (control) and following 20 minutes exposure to varying concentrations of nanosilver solution (1.25 mcg/ml and 2.50 mcg/ml) in rabbit carotid rings (+E or –E). Contractile responses were analysed with reference to maximal contractions induced by 80 mM K⁺. Dose relaxation tests to acetylcholine was examined in normal PSS (control), following 5 minutes exposure to L name or indomethacin and 20 minutes exposure to nanosilver solution (1.25 mcg/ml) in rabbit carotid rings. Relaxation responses were analysed with reference to maximal contraction induced by EC70 M PE in normal PSS. Data was presented as Mean ± SEM. Graphs and statistical analysis were done using Graphpad prism version 7.03 and Student t-test. P-value ≤ 0.05 were considered statistically significant. The results show that nanosilver induced attenuated contractile response in varying concentrations in +E and –E carotid rings. The results also show that nanosilver induced relaxation is endothelium dependent, and nanosilver showed a biphasic effect. In conclusion, the study shows that NSPs has a biphasic effect on vascular tone and NSPs induced relaxation is endothelium dependent. Further studies should be carried out to determine the mechanism of action of NSPs and the adverse effects associated with NSPs.