Purchase this article with an account.
Y.-C. Lee, H.-H. Chang, C.-H. Liu, M.-F. Chen, P.-Y. Chen, J.-S. Kuo, T.-F. Lee; Methyl Palmitate: A Potent Vasodilator Released in the Retina. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6448.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine if palmitic acid methyl ester (PAME) or methyl palmitate is the retina-derived relaxing factor (RRF).
A superfusion bioassay cascade technique was used with rat isolated retina as donor tissue and rat aortic ring as detector tissue. The superfusate was analyzed with gas chromatography/mass spectrometry (GC/MS). The biochemical and pharmacological characteristics of RRF and PAME were compared.
We demonstrated that the retina upon superfusion with Krebs’ solution spontaneously released RRF (indicated by aortic ring relaxation) and PAME (measured by GC/MS). The release of RRF and PAME was calcium-dependent, since the release was abolished when the retinas were superfused with calcium-free Krebs’ solution. Furthermore, aortic relaxations induced by RRF and PAME were not affected after heating their solutions at 70°C for 1 hr, suggesting that both are heat stable. Exogenous PAME concentration-dependently induced aortic relaxation with EC50 of 0.82±0.75 pmol/L. The aortic relaxations induced by RRF and exogenous PAME were inhibited by 4-aminopyridine (4-AP, 2 mmol/L) and tetraethylammonium (TEA, 10 mmol/L), but were not affected by TEA at 1 mmol/L or 3 mmol/L, glibenclamide (3 µmol/L), or iberiotoxin (100 nmol/L). The vasodilator activity of Krebs’ solution containing RRF or exogenous PAME was greatly attenuated following hexane extraction.
RRF and PAME share similar biochemical properties and react similarly to all pharmacological inhibitors examined. Both act primarily on the voltage-dependent K+ (Kv) channel of aortic smooth muscle cells, causing aortic relaxation. These results suggest that PAME is the hydrophobic RRF.
This PDF is available to Subscribers Only