Insulin‐induced dilatation of porcine retinal vessels in vitro is most pronounced in precapillary arterioles

Abstract

PurposeImpaired retinal blood flow is involved in the pathophysiology of diabetic retinopathy, and it has been shown that the smaller and larger retinal vessels may contribute differently to these flow changes. Diabetes mellitus is accompanied with changes in a number of metabolic parameters including a reduced effect of insulin. However, the vasoactive effects of insulin on retinal vessels with different calibers have not been studied in detail.MethodsPorcine hemiretinas were mounted in a newly established experimental model specifically developed for studying diameter changes of retinal vessels with different caliber. Changes in the diameter of larger arterioles (25 μm or larger), pre‐capillary arterioles (10‐25 μm) and capillaries (smaller than 10 μm) were studied after intravascular and extravascular addition of insulin in retinal vessels preconstricted with the prostaglandin analogue U46619 from altogether 6 hemiretinas from different animals.ResultsInsulin dilated preconstricted arterioles and pre‐capillary arterioles significantly after both intravascular and extravascular application (p < 0.01 for all comparisons), but had no significant effect on the diameter of capillaries after intravascular (p > 0.07) and extravascular (p > 0.31) application. The dilating effect of insulin was significantly more pronounced for pre‐capillary arterioles than for the two other vessel types after extravascular application (p < 0.01).ConclusionsInsulin dilates preconstricted retinal vessels, but the effect is most pronounced in pre‐capillary arterioles. This may have importance for understanding disturbances in retinal blood flow in diabetic retinopathy.