Mechanisms responsible for postmenopausal hypertension in a rat model: Roles of the renal sympathetic nervous system and the renin–angiotensin system
Rodrigo O. Maranon and Jane F. Reckelhoff
Physiol Rep. 2016 Jan; 4(2): e12669.
Rodrigo O. Maranon (USA)
1) Summarize your work in one sentence.
We tested if the renal denervation would lower the blood pressure in old female SHR, thus reducing renin release and angiotensin II synthesis, and thus would attenuate the antihypertensive effects of AT1 receptor antagonism.
2) Summarize your findings in one sentence.
We found that both the renal sympathetic nervous system and the RAS play distinct, independent roles in mediating hypertension in old female SHR.
3) Which were the more important methods you used in this work? If it is not a traditional method, you can briefly explain the concept of that methodology.
The more important methods that we did in this work was the renal denervation and the implantation of the telemetry probes in the same surgical time. Briefly, under 5% isoflurane anesthesia, the left renal artery was exposed via a midline incision, and, with the use of a dissecting microscope, the renal nerves were isolated and cut. To ensure complete removal of nerve fibers, the renal arteries were painted with a 10% phenol in ethanol solution. Then, the abdominal aorta was exposed, and telemetry probe was implanted.
4) What did you learn from this paper, what was your take-home message?
This paper taught us that both the renal sympathetic nervous system and the renin-angiotensin system play distinct, independent roles in mediating hypertension in old female SHR. First, renal denervation in old female SHR signiﬁcantly reduces MAP compared to sham females. Second, losartan reduces MAP in both renal denervated and sham rats by the same percentage and numerical amount. Third, with the combination of renal denervation and losartan, the MAP remains signiﬁcantly elevated in the old females. Thus, our results do not support our hypothesis since we anticipated that renal denervation would attenuate the effect of losartan to reduce blood pressure in our old female SHR.
Hypertension in aging women has been shown in many studies to be less well controlled than in age-matched men (National Center for Health Statistics, Health, United States, 2011). The reasons for this are unknown. Our data suggest that there may be different mechanisms responsible for essential hypertension in men and women and that these mechanisms may change with advancing age. More precisely, our data suggest that similar mechanisms, but to different extents, may be contributing to elevated blood pressure in aging men and women. Also, it is possible that the efﬁcacy to antihypertensive medications may be different in men and women and only a few studies of this type have been done to date since most of the studies combine the data for men and women and do not evaluate the genders separately. In this age of individualized, personalized medicine, the guidelines for antihypertensive treatment should be re-evaluated and studies done with these concepts and questions in mind.