Massicotte G, St-Louis J, Schiffrin E L
Experimental Hypertension Laboratory, Clinical Research Institute of Montreal, Quebec, Canada.
Proc Soc Exp Biol Med. 1987 Dec;186(3):294-8. doi: 10.3181/00379727-186-42616.
Gestation in the human and in rats is accompanied by a decrease in blood pressure and a reduction of the pressor response to vasoconstrictor agents. In humans, the decreased vascular reactivity to angiotensin II (AII) may occur simultaneously with a state of increased baroreceptor sensitivity. We have consequently evaluated the heart rate response to elevation of blood pressure following administration of either AII or arginine8-vasopressin (AVP) in conscious unrestrained, nonpregnant, or term-pregnant normotensive rats (Sprague-Dawley, SDR; Wistar-Kyoto, WKR) and in spontaneously hypertensive rats (SHR). The decrease in heart rate in response to increase in blood pressure by AII in nonpregnant animals was similar in SDR and SHR, but much greater in WKR. The heart rate response to increase in blood pressure by AVP was similar in all three strains of cycling rats. Gestation (20th day) did not change the heart rate response to increase in blood pressure by AII in normotensive animals, but increased slightly the reflex responses in SHR, as shown by a significant increase of the slope of the relationship of the decrement in heart rate versus the increment of blood pressure. The heart rate response to increase in blood pressure by AVP was greater during gestation in normotensive SDR and WKR, but not in SHR. These results show that the heart rate responses to an increase in blood pressure by vasoconstrictor peptides is dependent on the strain of animals used and suggest that the baroreceptor reflexes play a minor role in the blunted effect of vasconstrictor agens at the end of gestation in normotensive and spontaneously hypertensive rats.
人类和大鼠的妊娠期均伴有血压下降以及对血管收缩剂的升压反应减弱。在人类中，血管对血管紧张素II（AII）反应性降低可能与压力感受器敏感性增加的状态同时出现。因此，我们评估了在清醒无拘束、未怀孕或足月妊娠的正常血压大鼠（斯普拉格-道利大鼠，SDR；Wistar-Kyoto大鼠，WKR）以及自发性高血压大鼠（SHR）中，给予AII或精氨酸8-加压素（AVP）后，心率对血压升高的反应。在未怀孕的动物中，SDR和SHR对AII引起的血压升高的心率下降反应相似，但WKR的反应更大。在所有三种品系的性周期大鼠中，AVP引起的血压升高的心率反应相似。妊娠（第20天）并未改变正常血压动物对AII引起的血压升高的心率反应，但在SHR中略微增加了反射反应，表现为心率下降与血压升高关系曲线斜率的显著增加。在正常血压的SDR和WKR中，妊娠期间对AVP引起的血压升高的心率反应更大，但在SHR中并非如此。这些结果表明，血管收缩肽引起的血压升高的心率反应取决于所用动物的品系，并提示在正常血压和自发性高血压大鼠妊娠末期，压力感受器反射在血管收缩剂作用减弱中起次要作用。
