Integrative pattern of vasomotor efficiency in SHR during ontogenesis

Numerous studies concerning the cardiovascular system in SHRoften yield controversial data. The background of this diversityhas various roots, ranging from different vascular segments orareas studied up to the different age of experimental animals.Our study aimed to follow the BP as an integrated response ofvascular system. This approach was justified since stabilizedcardiac output in SHR was proved till 1 year of age. The groupsof male SHR (aged 3, 5, 9, 17 and 52 weeks) and age-matchedWistar rats were used. Significant basal BP difference betweenSHR and Wistar rats was found at 9 weeks of age and continuedtill the age of 52 weeks, reaching 189.6±11.9 mm Hg in SHR and117.3±6.9 mm Hg in Wistar rats (P<0.01). The significantdifference in BP increase to two doses of noradrenaline (0.1 μgand 1 μg) between SHR and control rats was also found at theage of 9 weeks. At 52 weeks the BP increment to two doses ofnoradrenaline was in SHR 19.7±2.0 mm Hg and 60.5±3.9 mm Hgand in Wistar rats 7.4±1.9 mm Hg and 40.5±3.2 mm Hg(P<0.01). The hypotensive response to acetylcholine (0.1 μg,1 μg and 10 μg) in SHR was enhanced at 17 weeks of age onlyand this amplification persisted till the age of 52 weeks. In 52-week-old SHR the hypotensive response to three doses was69.9±10.2 mm Hg, 87.5±11.8 mm Hg and 103.4±10.6 mm Hg,while in Wistar rats it was 37.4±4.2 mm Hg (P<0.01), 62.3±3.5mm Hg (P<0.01) and 73.5±2.8 mm Hg (P<0.05). In conclusion,the efficiency of cardiovascular system of SHR to respond tonoradrenaline was already enhanced from 9 weeks of age,whereas the response to acetylcholine was not augmentedbefore the age of 17 weeks.