Abstract
The objective of the study was to outline the characteristics of the development of hypertension and some neurohumoral, haematological and morphological factors contributing to development of high blood pressure in a genetic model of salt-sensitive rat. Characteristics of Dahl salt-sensitive (DS) rats, as compared to their Dahl salt-resistant (DR) controls were as follows: 1) DS rats display higher blood pressure and lower heart rate compared to DR rats as early as 1 month of age at weaning). They gradually develop hypertension at 2 months of age, irrespective of diet. Low-Na diet (0.5% NaCl) does not prevent hypertension but delays its development and ameliorates it. High Na-diet (8% NaCl) exacerbates hypertension. 2) DS rats have retardation in body weight gain. They develop mild hypochromic anaemia. 3) After 2 months of Na loading (3 months of age), DS rats express significantly increased Na and water retention and increased plasma volume by 15% compared to 2.8% increase in DR rats on high-Na diet. 4) DS rats showed renal parenchymal lesions, more pronounced after Na-loading, focal atrophy of cortical tubules, mesangial matrix expansion and glomerulosclerosis. Consistent with high blood pressure were changes in renal arterioles, fibromuscular proliferation, deposition of fibrinoid material in intima. 5) Sodium loading produced increased activity of the sympathetic nervous system (SNS), and sodium restriction reduced SNS responsiveness.
Highlights
In the early 1960s Dahl et al.[3] selectively bred rats for susceptibility (DS rats) or resistance (DR rats) to the hypertensive effect of a high-salt diet (8 % NaCl)
3) After 2 months of Na loading (3 months of age), DS rats express significantly increased Na and water retention and increased plasma volume by 15 % compared to 2.8 % increase in DR rats on high-Na diet
Blood pressure, catecholamines, humoral changes and alterations in body weight in the 4 experimental groups after 2 months on either a low-Na or high-Na diet and in the 2 control weanling groups are presented in Tables 1, 2 and Figs 1, 2
Summary
In the early 1960s Dahl et al.[3] selectively bred rats for susceptibility (DS rats) or resistance (DR rats) to the hypertensive effect of a high-salt diet (8 % NaCl). In the DR line the level of dietary salt intake had little effect on blood pressure, but in the DS line increased dietary salt caused markedly elevated blood pressure[15]. The response to salt is inherited and polygenic It has been estimated, using quantitative genetic techniques, that approximately 2–4 loci are involved in determining the variation in response to blood pressure difference between DS and DR rats[10]. Some of these loci have recently been defined[1,8,16]
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