ABSTRACT
BACKGROUND: Stroke-prone spontaneously hypertensive rat(SHRsp) is an animal model of hypertensive stroke commonly used. The species is hard to be maintained due to hypertension and easily affected by environmental factors, therefore the characteristics of stroke are always aberrated.OBJECTIVE: To observe the abilities of reproduction and maintaining the characteristics of hypertensive stroke in SHPsp.DESIGN: Observational controlled study based on rats.SETTING: Cardiovascular Disease Institute and Fuwai Hospital of Chinese Academy of Medical Sciences.MATERIALS: The experiment was conducted Cardiovascular Disease Institute and Fuwai Hospital of Chinese Academy of Medical Sciences during September 1999 to December 2001. Totally 93 pairs(186) strain SHRsp, 48stroke-prone spontaneously hypertensive rats of 8 weeks age as well as 98pairs(196) rats of normal blood pressure [Wistar Kyoto rat (WKY) ] were selected.METHODS: Brother sister mating method was used. And the conception rate, number of litter size(only calculating the litter size of mother rat not eating neonatal rats), rate of eating neonatal rats by mother rats were recorded and compared with those of WKY. The systolic pressure and heart rate of strain rat were measured when they were 12, 16 and 20 weeks old. In addition, 488-week SHRsp were loaded 10 g/L salty water to accelerate the occurrence of stroke and hypertension and executed when they naturally dead or 12 weeks after salty water load. The brain tissue was processed by H-E staining and observed under microscope to detect the incidence of stroke.MAIN OUTCOME MEASURES: Conception rate of female rats within 2years; litter rate of pregnant rats; eating, rate of eating neonatal rats by mother rats; systolic pressure of strain rat; heart rate; detection rate of stroke.RESULTS: Totally 93 pairs(186) strain rats of SHRsp, 98 pairs(196) WKY and 48 SHRsp of 8 weeks old entered the final analysis. In the first year there were 2 generations delivered, the average conception rate( 100% ) and average litter number (10.3 rats) of SHRsp were higher than those of WKY of the same term(90%, P ＜ 0. 001; 6. 5 rats, P ＜ 0. 001) . In the second year, there were 2 generations of which the conception rate and average litter number(89%, 8.2 rats) of SHRsp were higher than those of WKY(59%, P ＜ 0. 001; 4. 3 rats, P ＜ 0. 001). There were 87 SHRsp female rats and 67normal blood pressure rats pregnant within 2 years, the rate of eating neonatal rats within 4 weeks postnatal was 6% (5/87) which was lower than that of WKY(18%, 12/67), P ＞ 0.05. The systolic pressure of 12weeks old male rats and female rats was 191.6-223.8 mm Hg and 174. 2-196. 3 mm Hg respectively, while that of 16-week old and 20-week male rats were 219.0 -224. 9 mm Hg and 232.0 -242.6 mm Hg respectively. The blood pressure of SHRsp increased with the advancing of age. The heart rate of 12-week old male and female rats was 388-428 times per minute and 373-417times/minute respectively while that of 16-week and 20-week male rats were 392 -410 times per minute and 404-425 times per minute respectively. The pathological detection rate of 48 SHRsp was 81% (39/48).CONCLUSION: The reproduction ability of SHRsp is similar to normal rats. The blood pressure, heart rate and pathological examination of brain tissue of them all maintain the characteristics of hypertension and stroke so that they can be used as qualified experimental model.