A New Concept of the Pathogenesis of Retinopathy of Prematurity

The lecture provides a detailed description of the development of retinal vessels, vasculogenesis and angiogenesis. The cascade of protective mechanisms of the organism of the system of combating hyperoxia, the system of combating circulatory hypoxia and the key growth factors of the vascular endothelium during angiogenesis are shown. The pathogenesis of retinopathy of prematurity is described and the first phase of ROP development is analyzed in detail, the reasons for the delay in the maturation of vascular autoregulation are explained. The author proposed to distinguish the first preclinical phase in the ROP classification. In contrast to the modern concentration of attention of ophthalmologists on the active and cicatricial stages, the author proposes to pay special attention to the study of the preclinical stage of ROP, where its pathogenesis is formed.

Intraluminal hyperglycaemia causes conduit and resistance artery dilatation and inhibits vascular autoregulation in the anaesthetised pig

The effect of intraluminal hyperglycaemia was investigated in the iliac artery of 11 anaesthetised pigs. Following isolation of a test segment, hyperglycaemic blood (40 mmol·L–1) caused a significant dilatation of the artery of 167 ± 208 μm (mean ± SD; n = 6, P = 0.031). Dilatations were reduced by N(G)-nitro-l-arginine methyl esther (250 μg·mL–1) from 145 ± 199 to 38 ± 5 μm), but this was not statistically significant (n = 6, P = 0.18). Intra-arterial infusions of d-glucose (20–40 mmol·L–1·min–1), during graded constrictions, caused statistically significant increases in blood flow (n = 11, P = 0.0013). Vasodilatation was confirmed by measurements of the ratio of immediate pressure steps to flow steps (∂P/∂F) during the graded obstruction experiments, showing a decrease in instantaneous vascular resistance from a control of 0.62 ± 0.30 to 0.33 ± 0.34 mm Hg·mL–1·min–1 (n = 7, P = 0.016). Autoregulation was assessed from the slopes of the plots of steady-state flow versus pressure. There were significant increases in the slope from 2.32 ± 1.03 to 5.88 ± 5.60 mL·min–1·(mm Hg)–1 (n = 7, P = 0.0078), indicating significant impairment of autoregulation. In conclusion, luminal hyperglycaemia relaxes both arterial and resistance vessel smooth muscle.