Comparative study of various genetic hypertensive rat strains: blood pressure, body weight, growth and organ weights.

In an attempt to compare various genetic strains of hypertensive rats, representative hypertensive strains and associated controls (male, 1-month-old, 6-10 of each strain and 18 strains in total) were collected at a single center (National Institutes of Health; NIH, United States), maintained under the same experimental conditions with normal sodium NIH open formula diet and studied by a single investigator using standard techniques. Animals were measured for blood pressure (BP) by a tail-cuff method without anesthesia and body weight (BW) at 10 and 12 weeks of age and killed to measure organ weights. Hypertension was severe (> 190 mmHg) in spontaneously hypertensive rats (SHR) and their stroke-prone substrains at 12 weeks of age but mild to moderate (145-160 mmHg) in the rest of the hypertensive strains (Dahl's, Milan, Lyon, Sabra, and New Zealand Strains). Regarding organ size, partial correlation analysis showed that organ weights, except for brain and adrenal glands, are good functions of BW and that weight of the left ventricle (LV) was the only one significantly linked to BP levels. A bivariate regression model for LV weight was obtained as follows: LV(mg) = 1.478 BW(g) + 2.13BP(mmHg) - 51(R = 0.878, P < 0.001). The presence of some genetic factor regulating relative organ size independently of BW and BP was suggested in LV weight as well as in the weight of the other organs. Among the strains, MHS was found to be unique for the smallest kidney size and New Zealand strains for the greatest relative LV size when adjusted to allow for the influence of BP.(ABSTRACT TRUNCATED AT 250 WORDS)