To identify the causative substances for the shortening of survival time by rapeseed (
Canola) oil in
stroke-prone spontaneously hypertensive rats (SHRSP), SHRSP were fed on a standard chow supplemented with 10 w/w%
soybean oil (control),
rapeseed oil, one of the fractions of
rapeseed oil obtained by super critical gas extraction (SCE) under a pressure of 180-bar or 350-bar, at 40 degrees C, or the residue from the extraction (with 0.5% NaCl in
drinking water). In another series of experiment, SHRSP were fed for 8 weeks on the above-mentioned diets without
salt loading and autopsied.
Fatty acid compositions in these diets were similar, except in the
soybean oil diet, and
phytosterol contents were: (diet containing) 180-bar fraction>residue>
rapeseed oil>350-bar fraction>
soybean oil. Survival times in the
rapeseed oil, 350-bar fraction and residue groups were shorter than, whereas that in the 180-bar fraction was similar to in the
soybean oil group. In the 8-week feeding experiment, chronic nephropathy was found frequently in the groups other than the
soybean oil group. The heart weights were higher in the
rapeseed oil and residue groups. Cerebral
necrosis was found in the residue group. Taken together, the followings are concluded, (1) Neither the
fatty acid composition, nor the amount of
phytosterols in the diets appeared to be decisive in the shortening of life. (2) SCE appeared to produce a safe (180-bar) fraction, though it failed to separate clearly the causative substances into specific fractions. (3) The factors that facilitate the
genetic disease of SHRSP appear to exist in
rapeseed oil. However, they might not be identical to those responsible for the life-shortening, since there were no findings common across the
rapeseed oil, 350-bar and residue groups, which showed similar life-shortening.