Tail-cuff detection of systolic hypertension in different strains of ageing rats.

To identify rat strains suitable for studying age-related development of hypertension we compared pressures measured with the tail-cuff method in different groups of ageing Fischer 344, Wistar, or Sprague-Dawley rats. Preliminary experiments to establish optimal frequency of chronic blood pressure measurement in ageing rats showed that tail-cuff systolic pressures did not differ significantly whether taken weekly or monthly. Repeated tail-cuff measurements were comparable even when a common cuff size was used in different groups of rats with varying tail diameters. Additional studies were then carried out in 1-year old male Wistar and Sprague-Dawley rats to measure tail-cuff pressures monthly during the second year of age. Systolic and mean pressures increased progressively with age in both strains, as did body weight and heart rate, but the incidence of hypertension was higher in Sprague-Dawley than in Wistar rats. Elevations in mean pressures were sometimes more pronounced than those in systolic pressure. Two months after the last tail-cuff measurement, the presence of hypertension in Wistar rats was verified by the elevated mean pressures that were recorded from femoral artery catheters. Our results overall suggest that the predisposition to hypertension was higher in Sprague-Dawley than in Wistar or Fischer 344 rats of the same age, and also in males than in females of the same strain. Of all the different strains and sexes we compared, therefore, male Sprague-Dawley rats from 20 to 24 months of age may be the best model for studying the development of systolic hypertension with age.