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The effects of increased dietary salt on renal blood flow responses during physiological stress: Role of renin‐angiotensin system
Author(s) -
Momen Afsana,
Blaha Cheryl,
Thomas Karen,
Gahremanpour Amir,
Gray Kristen S.,
King Nicholas,
Leuenberger Urs A.,
Sinoway Lawrence I.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a565-b
Subject(s) - plasma renin activity , medicine , vasoconstriction , blood pressure , endocrinology , renal blood flow , baroreflex , vascular resistance , hemodynamics , renin–angiotensin system , angiotensin ii , mean arterial pressure , heart rate
Renal sympathetic nerve activation is essential for the development of stress‐induced hypertension. High dietary salt (HDS) also contributes to the development of some forms of hypertension. However, it is unclear whether HDS modulates sympathetically mediated renal vascular resistance (RVR) responses during physiological stress in humans. We hypothesized that renal vasoconstrictor responses during stress would be enhanced with HDS. Beat‐by‐beat measurements of renal blood flow velocity (RBV), blood pressure (BP) and heart rate were obtained in nine normotensive subjects during graded static handgrip (HG) and lower body negative pressure (LBNP) protocols before and after 7 days of HDS. RVR index was calculated by dividing mean BP by RBV. Baseline hemodynamics and plasma norepinephrine were unchanged whereas epinephrine was increased ( P < .01) with HDS. In contrast to our hypothesis, increases in RVR during 15 s HG at 70% maximum voluntary contraction were less ( P < .04) in the subjects who showed a “large” reduction (≥70%) in PRA after HDS. Importantly, the magnitude of this attenuation correlated directly to the drop in PRA after HDS (r = .84; P < .02). RVR responses were also less within the same subjects during LBNP at −10 mmHg after HDS ( P < .02) although the responses were similar at −30 and −50 mmHg. In conclusion, HDS attenuates the RVR responses during high intensity handgrip especially in subjects with a large reduction in PRA. We speculate that diminished renin‐angiotensin system after HDS led to enhanced arterial baroreflex restraint of the muscle mechanoreflex induced renal vasoconstriction during exercise. Supported by R01 HL070222 (Sinoway), P01 HL077670 (Sinoway) and M01 RR010732.