Remodeled structure and reduced contractile responsiveness of ocular ciliary artery in spontaneously hypertensive rats.

Abstract

To investigate the alterations in both structure and contractile responsiveness of ocular ciliary artery (OCA) in spontaneously hypertensive rat (SHR). In this experiment, 20-week-old male SHR and Wistar Kyoto rat (WKY) were studied. The heart rate (HR), the blood pressure (BP; the systolic BP and the diastolic BP) of rats with an electronic sphygmomanometer were measured. Vascular morphometry and isometric tension measurement were used to investigate the alterations in structure and contractility of OCA. A general narrowing of OCAs was observed in SHR compared to the control WYK. In SHR, the media of OCAs were thicker, the luminal diameters were smaller, and the media-to-lumen ratios were higher when compared with WKY (P<0.05). The contractions of OCAs evoked by norepinephrine were smaller in SHR compared to control (P<0.05). Then, OCAs were pretreated with iberiotoxin, L-NAME, or indomethacin 30min before norepinephrine-induced contraction. Iberiotoxin (0.1 µmol/L) has not changed the norepinephrine-induced contractions in OCAs from both groups. However, L-NAME (100 µmol/L) increased the vasoconstrictions, the increased extents were similar in SHR and WKY (P>0.05). Indomethacin (10 µmol/L) decreased the contractions induced by norepinephrine in OCAs from WKY (P<0.05), but did not change those contractions in vessels from SHR (P>0.05). Our results demonstrate that the structure and function of OCAs are altered in hypertension. OCAs from SHR are remodeled with decreased lumen diameter and increased media-to-lumen ratio. Moreover, the contractile responsiveness of OCAs from SHR is diminished due to the disruption of vasoconstrictive effect of prostaglandins.