A new model for studying diameter regulation of porcine retinal arterioles and capillaries in vitro

Abstract

Purpose Studies of diameter regulation in retinal arterioles in vitro have mostly been performed on larger vessels, but evidence suggests that perturbations in the retinal microcirculation may also play a role in the development of vision threatening retinal diseases. Therefore, the purpose of the present study was to develop an in vitro technique for studying diameter regulation in both larger and smaller vessels. Methods A special tissue chamber was developed for mounting, cannulating and perfusing porcine hemiretinas while controlling temperature, pH and oxygen saturation. The chamber was mounted in a flourescens microscope, and the effect on the diameter of larger arterioles, pre‐capillary arterioles and capillaries was studied after intravascular and extravascular addition of the thromboxane analogue U46619 and lactate (n=6 for each variable) and NMDA (preliminary). Results In all vessel calibers the thromboxane analogue U46619 induced a significant contraction after extraluminal application (p<0.02), but not after intraluminal (p>0.13). Lactate had no effect on the diameter of non‐precontracted vessels (p>0.21), but in pre‐contracted vessels lactate relaxed the vessel diameter. Conclusion The response to vasoactive compounds is different after intraluminal and extraluminal application, and the diameter response of vasoactive compounds is different in larger and smaller retinal vessels. The dilating effect of lactate depends on the state of contraction of the retinal vessel.