Abstract
Purpose:
Recently, a novel population of perivascular cells located immediately external to the vascular smooth muscle cells of the retinal arterioles has been identified. Perivascular cells share common characteristics with pericytes and contribute to agonist-induced modulation of retinal arterioles tone. The purpose of this study was to identify the source of Ca2+ in the perivascular cells during PGE2-induced relaxation of retinal arterioles.
Methods:
Porcine retinal arterioles with preserved perivascular retinal tissue were mounted in a confocal myograph, were placed in a confocal microscope and loaded with a Ca2+-sensitive fluorophore Oregon Green. The arterioles were preconstricted with 10-6 M U46619, and PGE2 (10-5 M) was added. Vascular tone and fluorescence from the retinal perivascular cells were recorded simultaneously using LabChart 7 and LSM-5 Pascal programs respectively.
Results:
The addition of PGE2 induced significant relaxation (p<0.05) and Ca2+ activity in retinal perivascular cells. However, neither arteriolar relaxation nor Ca2+ activity of retinal perivascular cells in response to PGE2 were affected by pharmacological blockade of L-type Ca2+ channels, non-specific cation channels or ryanodine receptors.
Conclusions:
PGE2-induced relaxation of porcine retinal arterioles in vitro is associated with Ca2+ activity in perivascular retinal cells. The source of this calcium activity is different from ryanodine receptor channels, non-specific cation channels or channels and L-type Ca2+ channels.
Keywords: 688 retina •
439 calcium •
715 signal transduction: pharmacology/physiology