期刊
JOURNAL OF HYPERTENSION
卷 30, 期 9, 页码 1817-1826出版社
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1097/HJH.0b013e328356399b
关键词
aging; cyclic guanosine monophosphate; dietary sodium; hypertension; marinobufagenin; Na/K-ATPase; natriuretic peptides; protein kinase G; salt sensitivity
资金
- National Institute on Aging, NIH
Background: Marinobufagenin (MBG) promotes natriuresis via inhibition of renotubular Na/K-ATPase (NKA) and causes vasoconstriction via inhibition of vascular NKA. Atrial natriuretic peptide (ANP), via cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG)-dependent mechanism, sensitizes renal NKA to MBG but reduces MBG-induced inhibition of vascular NKA. As aging is associated with a downregulation of cGMP/PKG signaling, we hypothesized that in older rats, ANP would not potentiate renal effects of MBG and would not oppose vascular effects of MBG. Methods: In younger (3-month-old) and older (12-month-old) Sprague-Dawley rats, we compared SBP, natriuresis, activity of NKA in aorta and renal medulla, and levels of MBG and alpha-ANP at baseline and following acute NaCl loading (20%, 2.5 ml/kg, intraperitoneally), and studied modulation of MBG-induced NKA inhibition by alpha-ANP in vitro. Results: As compared with younger rats, NaCl-loaded older rats exhibited a greater MBG response, greater SBP elevation (25 vs. 10 mmHg, P < 0.01) and greater inhibition of NKA in aorta (39 vs. 7%, P < 0.01), 30% less natriuresis, and less inhibition of renal NKA (25 vs. 42%, P < 0.05) in the presence of comparable responses of alpha-ANP and cGMP. In aorta and kidney of older rats, the levels of PKG were reduced, the levels of phosphodiesterase-5 were increased compared with that in young rats, and alpha-ANP failed to modulate MBG-induced NKA inhibition. Conclusion: Age-associated downregulation of cGMP/PKG-dependent signaling impairs the ability of ANP to modulate the effects of MBG on the sodium pump, which contributes to salt sensitivity.
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