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Afferent arteriolar diameter in DOCA-salt and two-kidney one-clip hypertensive rats
Abstract:
The afferent arteriolar diameter (dAA) was investigated during development of hypertensive renal disease in normal and uninephrectomized control rats, in chronic DOCA-salt (DOCA), post-DOCA (p-DOCA), and chronic two-kidney one-clip (2K-1C) hypertensive rats, and in post-two-kidney one-clip (p-2K-1C) normotensive rats. dAA was measured by the microsphere method. Nephron loss was present in the kidneys exposed to elevate blood pressure. The dAA was reduced from 19.9 to 17.2 micron in the DOCA group (P less than 0.001) and from 19.1 to 16.3 micron in the nonclipped kidneys in the 2K-1C group (P less than 0.001). The dAA increased from 19.9 to 20.7 micron in the p-DOCA group. Afferent arteriolar dilatation from 19.1 to 21.0 micron (P less than 0.001) was present about 50 days after clipping in the 2K-1C group; in the clipped kidneys the dAA returned to normal (18.9 micron) after declipping. No relation between the dAA and plasma renin concentration was observed. In all models dAA was the same in three cortical layers of equal thickness. Accordingly, chronic renal DOCA-salt hypertension constricts the afferent arteriole with angiotensin-independent mechanisms. Autoregulatory dilatation of the afferent arteriole seems to be maintained for at least 50 days. When the hypertension is moderate, dAA in damaged kidneys may be dilated.
Insights
Chronic hypertension constricts afferent arterioles via angiotensin-independent mechanisms, but autoregulatory dilatation can occur in moderate hypertension, impacting damaged kidneys.
Area of Science:
- Nephrology
- Cardiovascular Physiology
- Renal Hypertension
Background:
- Hypertensive renal disease involves changes in renal hemodynamics.
- The afferent arteriole plays a critical role in regulating glomerular filtration.
- Understanding afferent arteriolar diameter (dAA) changes is key to renal disease progression.
Purpose of the Study:
- To investigate the afferent arteriolar diameter (dAA) during the development of hypertensive renal disease.
- To examine dAA changes in various rat models of hypertension, including DOCA-salt and two-kidney one-clip models.
- To determine the role of angiotensin and autoregulation in dAA modulation.
Main Methods:
- Utilized microsphere method for precise dAA measurement in rat models.
- Investigated normal, uninephrectomized, DOCA-salt, post-DOCA, two-kidney one-clip, and post-two-kidney one-clip rats.
- Assessed dAA across different cortical layers and correlated with plasma renin concentration.
Main Results:
- Chronic DOCA-salt hypertension significantly reduced dAA (19.9 to 17.2 µm), indicating constriction.
- Non-clipped kidneys in 2K-1C rats showed reduced dAA (19.1 to 16.3 µm).
- Autoregulatory dilatation of dAA (19.1 to 21.0 µm) was observed in 2K-1C rats around 50 days post-clipping, with normalization after declipping.
Conclusions:
- Chronic renal DOCA-salt hypertension constricts the afferent arteriole through angiotensin-independent pathways.
- Autoregulatory dilatation of the afferent arteriole is maintained for at least 50 days.
- Moderate hypertension may lead to afferent arteriolar dilatation in damaged kidneys.