A novel technique to study the time course of morphological and functional vascular responses to hypertension in conscious rats

Abstract

Assessment of morphological vascular responses to exposure to cardiovascular risk factors in experimental animals requires ex vivo experiments that do not allow assessment of the time course of vascular alterations in individual subjects. We used a slit‐lamp biomicroscope (resolution <1 μm) to photograph the long posterior ciliary artery (LPCA) of the iris in conscious normotensive Wistar Kyoto rats (WKY, n=10) and spontaneously hypertensive rats (SHR, n=10) on regular‐salt diet (RS) and in SHR (n=10) on high‐salt diet (HS). The same segment along the LPCA was imaged in consecutive weekly imaging sessions and an imaging software was used to determine the wall to lumen (W/L) ratio. After 4 weeks systolic blood pressure (SBP) did not change in WKY (115±5 vs. 111±5 mmHg) and SHR‐RS (148±7 vs. 155±3 mmHg) but increased significantly in SHR‐HS (139±5 mmHg vs. 166±6 mmHg, p<0.05). The time course of the changes in W/L ratio of the LPCA mirrored the time course of the SBP changes. While W/L ratio did not change in WKY‐RS (+12±10%) and SHR‐RS (+18±17%), there was a 39±14% increase in W/L ratio in SHR‐HS. Since the LPCA was not dilated pharmacologically the W/L ratio assessed in this study may reflect the combination of morphologic alterations and changes in vascular tone. In vivo imaging of the LPCA may allow assessment of the time course of morphological and functional vascular responses to hypertension in conscious rats. (Supported by the American Heart Association)