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High pressure diuresis initiates malignant hypertension in the young
Insights
Infantile rats develop severe hypertension more rapidly than adults due to higher renin-angiotensin-aldosterone system activation. Their kidneys exhibit pronounced high-pressure diuresis at lower blood pressures during maturation.
Area of Science:
- Nephrology
- Pediatric Hypertension
- Renal Physiology
Background:
- Severe hypertension can lead to symptoms like weight loss, polydipsia, polyuria, and hyponatremia.
- The role of kidney maturation in the development of hypertension and associated diuresis is not fully understood.
Purpose of the Study:
- To investigate the impact of kidney maturation on the development of renin-induced hypertension and high-pressure diuresis.
- To compare the hypertensive response and diuresis in infantile versus adult rats.
Main Methods:
- Renal artery clipping was performed on infantile (18-day-old) and adult (40-day-old) Sprague-Dawley rats to induce hypertension.
- Blood pressure, body weight, fluid intake, plasma renin concentration, and aldosterone levels were monitored.
Main Results:
- Infantile rats exhibited a steeper blood pressure increase (7.8 mmHg/day) compared to adult rats (3.2 mmHg/day).
- High-pressure diuresis, indicated by weight loss, occurred at lower systolic blood pressure levels (140-150 mmHg) in infantile rats versus adult rats (180 mmHg).
- Plasma renin and aldosterone levels were twofold higher in infantile rats, correlating with increased fluid intake.
Conclusions:
- The immature kidney in infantile rats shows a heightened renin-angiotensin-aldosterone system response, leading to accelerated hypertension.
- Kidney maturation is associated with an increased threshold for high-pressure diuresis and a reduced overall diuretic response.
Abstract:
Weight loss, polydipsia, polyuria, hyponatremia are symptoms often seen in patients with severe renin-induced hypertension. To investigate the role of the maturing kidney in the development of high pressure diuresis hypertension was induced in infantile (18 days old) and adult (40 days old) Sprague-Dawley rats by clipping one renal artery. In infantile rats blood pressure increase was steeper than in adult rats (7.8 vs. 3.2 mmHg/day). High pressure diuresis resulting in body weight loss was observed at systolic blood pressure levels of about 140 to 150 mmHg in infantile animals compared to 180 mmHg in adult rats. At this time fluid intake was increased to 64 in infantile and 30 ml/100 g body weight/day in adult rats. Plasma renin concentration and aldosterone were two fold higher in infantile than in adult rats. The data show that infantile rats, due to a higher activation of the renin-angiotensin-aldosterone system, have a steeper blood pressure increase and, furthermore, that during maturation of the kidney high pressure diuresis starts at lower blood pressure levels and is much more pronounced.