Renal function and functional reserve in healthy elderly individuals.
BACKGROUND
Aging is characterized by a decline in renal function and by a susceptibility to renal diseases. However it is not clear whether the observed changes are solely hemodynamic, structural or both. We evaluated renal function, functional reserve (RFR) and morphology in healthy elderly individuals.


METHODS
Healthy participants (n=19) were divided into young (n=6, age range 25-37 years), middle-aged (n=6, 44-74 years) and elderly (n=7, 81-96 years). Nitric oxide (NO), plasma renin activity (PRA) and aldosterone, renal plasma flow (RPF) by p-aminohippurate clearance (CPAH) and glomerular filtration rate (GFR) by inulin clearance (CIN) were determined before and during maximal vasodilating stimuli, induced with the infusion of dopamine and amino acids. Glomerular sclerosis, lumen area and wall thickness of afferent arterioles were determined by kidney biopsy from 36 healthy kidney donors and from 6 nephrectomies for renal carcinoma.


RESULTS
GFR and RPF were slightly reduced in elderly individuals whereas filtration fraction (FF) was increased. GFR and RPF did not increase in the elderly after maximal vasodilating stimuli as in young and middle-aged subjects suggesting a reduction of RFR. NO, increased at baseline, did not increase further after vasodilating stimuli; while on the contrary, PRA, similar in the 3 groups at baseline, was not reduced by vasodilating stimuli in the elderly. Sclerotic glomeruli but not glomerular volume were significantly increased by aging. Afferent arteriole lumens were reduced by aging whereas wall thickness was unchanged.


CONCLUSIONS
Renal function is preserved with aging in healthy subjects at the expense of a complete reduction of RFR. RFR may be wasted to compensate for the increased number of sclerotic glomeruli. Vascular changes, suggested by reduced arteriolar lumen, may be so advanced that even in the presence of high levels of vasodilatory molecules, kidneys are not responsive anymore to maximal vasoactive stimuli.
Esposito
Ciro
C
Unit of Nephrology, Dialysis and Transplantation, IRCCS Policlinico San Matteo, University of Pavia, Pavia - Italy. espositociro56@hotmail.com
Plati
AnnaRita
A
Mazzullo
Tiziana
T
Fasoli
Gianluca
G
De Mauri
Andreana
A
Grosjean
Fabrizio
F
Mangione
Filippo
F
Castoldi
Francesca
F
Serpieri
Nicoletta
N
Cornacchia
Flavia
F
Dal Canton
Antonio
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism / Q000473:pathology; D000450:Aldosterone / Q000097:blood; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D007677:Kidney Function Tests; D007678:Kidney Glomerulus / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood; D012016:Reference Values; D012079:Renal Circulation / Q000187:drug effects; D012083:Renin / Q000097:blood; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D009569:Nitric Oxide; D000450:Aldosterone; D012083:Renin