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Salt sensitivity of renin secretion, glomerular filtration rate and blood pressure in conscious S prague‐ D awley rats
Author(s) -
Isaksson G. L.,
Stubbe J.,
Lyngs Hansen P.,
Jensen B. L.,
Bie P.
Publication year - 2014
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/apha.12191
Subject(s) - plasma renin activity , renal function , endocrinology , chemistry , medicine , blood pressure , renin–angiotensin system , saline , sodium , aldosterone , organic chemistry
Abstract Aim We hypothesized that in normal rats in metabolic steady state, (i) the plasma renin concentration ( PRC ) is log‐linearly related to Na + intake (NaI), (ii) the concurrent changes in mean arterial pressure ( MABP ) and glomerular filtration rate ( GFR ) are negligible and (iii) the function PRC = f(NaI) is altered by β 1 ‐adrenoceptor blockade (metoprolol) and surgical renal denervation ( DNX ). Methods In catheterized, conscious rats on low‐Na + diet (0.004% Na + ), NaI was increased by up to 120‐fold, in four 3‐day steps, by intravenous saline infusion. MABP was recorded continuously, PRC measured in arterial blood, and GFR estimated by inulin clearance. Results Steady states were achieved within 3 days. PRC [mIU L −1 ] was log‐linearly related to NaI [mmol kg −1 day −1 ]: PRC = −9.9 log (NaI) + 22. Set point (22 mIU L −1 at NaI = 1) and slope (9.9 mIU per decade NaI) were independent of metoprolol administration and DNX . MABP and GFR were markedly salt‐sensitive: MABP [mmHg] = 4.9 log (NaI) + 99 ( P < 0.01), and GFR [mL min −1 ] = 1.4 log (NaI) + 8.3 ( P < 0.01). MABP increased similarly (approx. 10%, P < 0.001) irrespective of pre‐treatment. Metoprolol, but not DNX , reduced MABP , HR , and GFR (all P < 0.01). Salt sensitivity of GFR was not observed in DNX rats. Conclusion Log‐linear relations to sodium intake exist not only for PRC , but also for MABP and GFR , which per 10‐fold increase in sodium intake rose by 5 mmHg and 1.4 mL min −1 respectively. Steady‐state levels of PRC appear independent of renal nerves. MABP and GFR seem markedly salt sensitive in normal rats.