Response of hypertensive rats to acute and chronic conditions of static exercise

To determine whether chronic static exercise would alter resting caudal artery systolic blood pressure (RSBP) in stroke-prone hypertensive rats (SP-SHR), a 20- to 21-wk experimental study was initiated with 24 male and 16 female rats. In addition, eight rats were cannulated for heart rate and blood pressure measurements and implemented with Doppler flow probes (mesenteric and iliac arteries) for determination of the acute responses. The rats were trained to perform static exercise by forelimb hanging over an electrical grid (3-5 mA) activated with a high-frequency sound (2.5-10kHz) of 60 dB. Acute forelimb hanging by nontrained rats caused a 70-mmHg elevation in mean blood pressure, 115-beat/min increase in heart rate, and 71% decrease in mesenteric blood flow. The procedure for chronic forelimb hanging included increasing the number of sets per session from one to three, maintaining the number of repetitions between 6 and 10 and the hang time within 7-10 s/hang, while increasing the amount of weight supported per set from 0 to 12% of body weights for males and 30% for females. Two performance tests, one for endurance (no weights) and one for "strength" (weights), demonstrated that the hanging animals increased their endurance ability by 103% and their strength by 115%. RSBP was not significantly increased in either the male or female trained populations when evaluated by analysis of variance or trend-analysis procedures. Food and water consumption, sodium and potassium excretion, and blood volume measurements exhibited no group differences that had statistical significance. Five animals had evidence for previous strokes, with four being associated with the nonhanging animals.(ABSTRACT TRUNCATED AT 250 WORDS)