Abstract
Purpose: :
A recent study has identified a cellular bouton structure external to vascular smooth muscle cells, which is activated when ATP induces vasorelaxation in porcine retinal arterioles. The purpose of the present study was to identify possible pericyte characteristics of this perivascular cell structure, and to study its involvement in adenosine induced vasorelaxation stimulated by NMDA, ATP and PGE2.
Methods: :
The cellular components of porcine retinal arterioles were studied by immunohistochemistry using primary antibodies against the pericyte markers NG2, desmin and CD13. Additionally, porcine retinal arterioles (≈ 150 μm) were mounted in a myograph and placed in a confocal microscope. After loading with a calcium sensitive fluorophore and pre-contraction with 10-6 M U46619, concentration-response experiments were performed with ATP (10-8 M to 10-4 M) and prostaglandin E2 (10-9 M to 10-5 M) during recording of retinal vascular tone and intracellular fluorescence in the vascular wall (n=6 for all experimental conditions).
Results: :
The perivascular cell structure showed immunoreactivity to the pericyte marker NG2, but not to desmin and CD13. ATP and PGE2, but not NMDA, induced a concentration-dependent relaxation of the retinal arterioles (p<0.01) simultaneously with the generation of calcium activity in the perivascular structures.
Conclusions: :
ATP and PGE2 induced relaxation of porcine retinal arterioles are mediated by cellular elements with pericyte characteristics external to the vascular smooth muscle cells. The function of of these pericytes may be a potential target for future pharmacological intervention on vascular disturbances in retinal disease.
Keywords: retinal connections, networks, circuitry • immunohistochemistry • signal transduction: pharmacology/physiology