ABSENCE OF HYPERTENSION IN DOGS WITH RENAL-INSUFFICIENCY

Dogs have provided classic models of induced hypertension. This paper shows that despite being susceptible to hypertension, they are natural ly resistant to its development even. when renal function is severely compromised. The proportion of hypertensive dogs was almost as low amo ng those with reduced glomerular filtration rate (GFR) (9%) as those w ith normal GFR (6%). Dogs with GFR less than 33% of the normal lower l imit (with an average GFR equivalent to 10 mt min(-1) in a 70-kg patie nt) had arterial pressures not significantly above normal. Only dogs w ith a GFR 33-75% of the lower limit of normal had significantly elevat ed systolic pressure, though none was actually hypertensive. Since the re was no correlation between arterial pressure and GFR below 33% of l ower limit, the dogs in the 33-75% range may be showing an effect of i ncreased pressure, rather than a cause. In humans with GFR less than 3 3% of normal, the majority are hypertensive. Since various aspects of canine cardiovascular and renal function are comparable with humans, t he question is why dogs, despite being capable of developing hypertens ion, are resistant to it, even when they have chronic renal insufficie ncy.