Venule distension properties in Wistar, Wistar-Kyoto, and spontaneously hypertensive rats

The purpose of this study was to determine whether venule distension characteristics are modified in denervated venules in the spontaneously hypertensive rat (SHR) during the developmental stage of hypertension. The distension of denervated first-order venules (1V) and small collecting veins (SCV) in the intestine of 7- to 8-wk-old SHR, Wistar-Kyoto (WKY), and Wistar rats were measured with intravital microscopy during venous pressure elevation. Diameter strain and distensibility were calculated for the 1V and SCV from vessel diameter and servo-null pressure. The Wistar 1V underwent larger strains and distensibilities than the WKY or SHR vessels, which had similar characteristics. For the SCV, the Wistar and WKY strains and distensibilities were similar, with the SHR different from these at only certain pressure elevations. Thus no consistent patterns of altered distension characteristics were found in denervated SHR SCV or 1V compared with its controls. This study does not distinguish between changes in local active and passive factors in the vessel wall which may influence distension. Our results may be consistent with disease mechanisms in the 7- to 8-wk-old SHR which leave these local factors unchanged or with mechanisms which have local venular effects that counterbalance each other, leaving the distension behavior of the denervated venules unchanged.