Abstract
Purpose:
Studies of diameter regulation in retinal arterioles in vitro have hitherto mostly been performed on larger retinal arterioles, but it is known that the regulation of the retinal capillaries differs from that of the larger vessels. Therefore, the purpose of the present study was to develop an in vitro technique for studying diameter regulation in both arterioles and capillaries.
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.
Results:
In all vessel calibers the thromboxane analogue U46619 induced significant contraction after addition extraluminally (p< 0.04), but not intraluminally (p>0.12). Lactate had no effect on the diameter of non-precontracted vessels (p>0.23). In contracted vessels lactate had no effect on arterioles, but a heterogenous effect on pre-capillary artererioles and capillaries.
Conclusions:
The vasoactive effects of lactate on retinal vessels require that the vessel is precontracted and differs between arterioles, pre-capillary arterioles and capillaries. The study confirms that evidence about the diameter regulation of retinal arterioles does not necessarily reflect diameter regulation in the retinal capillary system.
Keywords: 436 blood supply •
688 retina