TY - JOUR
T1 - Altered responsiveness of the kidney to activation of the renal nerves in fat-fed rabbits
AU - Michaels, Sylvia
AU - Eppel, Gabriela Alejandra
AU - Burke, Sandra L
AU - Head, Geoffrey Albert
AU - Armitage, James
AU - Carroll, Joan F
AU - Malpas, Simon C
AU - Evans, Roger George
PY - 2009
Y1 - 2009
N2 - We tested whether mild adiposity alters responsiveness of the kidney to activation of the renal sympathetic nerves. After rabbits were fed a high-fat or control diet for 9 weeks, responses to reflex activation of renal sympathetic nerve activity (RSNA) with hypoxia and electrical stimulation of the renal nerves (RNS) were examined under pentobarbital anesthesia. Fat pad mass and body weight were respectively 74 and 6 greater in fat-fed rabbits than controls. RNS produced frequency-dependent reductions in renal blood flow, cortical and medullary perfusion, glomerular filtration rate, urine flow and sodium excretion and increased renal plasma renin activity (PRA) overflow. Responses of sodium excretion and medullary perfusion were significantly enhanced by fat-feeding. For example, 1 Hz RNS reduced sodium excretion by 79 +/- 4 in fat-fed rabbits and 46 +/- 13 in controls. Two Hz RNS reduced medullary perfusion by 38 +/- 11 in fat-fed rabbits and 9 +/- 4 in controls. Hypoxia doubled RSNA, increased renal PRA overflow and medullary perfusion, and reduced urine flow and sodium excretion, without significantly altering mean arterial pressure (MAP) or cortical perfusion. These effects were indistinguishable in fat-fed and control rabbits. Neither MAP nor PRA were significantly greater in conscious fat-fed than control rabbits. These observations suggest that mild excess adiposity can augment the antinatriuretic response to renal nerve activation by RNS, possibly through altered neural control of medullary perfusion. Thus, sodium retention in obesity might be driven not only by increased RSNA, but also by increased responsiveness of the kidney to RSNA. Key words: Hypertension, hypoxia, kidney circulation, obesity.
AB - We tested whether mild adiposity alters responsiveness of the kidney to activation of the renal sympathetic nerves. After rabbits were fed a high-fat or control diet for 9 weeks, responses to reflex activation of renal sympathetic nerve activity (RSNA) with hypoxia and electrical stimulation of the renal nerves (RNS) were examined under pentobarbital anesthesia. Fat pad mass and body weight were respectively 74 and 6 greater in fat-fed rabbits than controls. RNS produced frequency-dependent reductions in renal blood flow, cortical and medullary perfusion, glomerular filtration rate, urine flow and sodium excretion and increased renal plasma renin activity (PRA) overflow. Responses of sodium excretion and medullary perfusion were significantly enhanced by fat-feeding. For example, 1 Hz RNS reduced sodium excretion by 79 +/- 4 in fat-fed rabbits and 46 +/- 13 in controls. Two Hz RNS reduced medullary perfusion by 38 +/- 11 in fat-fed rabbits and 9 +/- 4 in controls. Hypoxia doubled RSNA, increased renal PRA overflow and medullary perfusion, and reduced urine flow and sodium excretion, without significantly altering mean arterial pressure (MAP) or cortical perfusion. These effects were indistinguishable in fat-fed and control rabbits. Neither MAP nor PRA were significantly greater in conscious fat-fed than control rabbits. These observations suggest that mild excess adiposity can augment the antinatriuretic response to renal nerve activation by RNS, possibly through altered neural control of medullary perfusion. Thus, sodium retention in obesity might be driven not only by increased RSNA, but also by increased responsiveness of the kidney to RSNA. Key words: Hypertension, hypoxia, kidney circulation, obesity.
UR - http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=19321699
U2 - 10.1152/ajpregu.90931.2008
DO - 10.1152/ajpregu.90931.2008
M3 - Article
SN - 0363-6119
VL - 296
SP - R1889 - R1896
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
IS - 6
ER -