Glomerular hypertension and hyperfiltration in adrenocorticotrophin-induced hypertension in rats: the role of nitric oxide.
OBJECTIVE
To determine the effects on pre- and post-glomerular vascular resistance of adrenocorticotrophin (ACTH)-induced hypertension in rats, before and after blockade of nitric oxide formation.


METHODS
Four groups of Sprague-Dawley rats were studied. Measurements were made in ACTH- (Synacthen Depot, 0.25 mg/kg twice daily for 8 days) and sham-treated anaesthetized rats, before and after either Nomega-nitro-L-arginine (L-NNA, 6 mg/kg) or vehicle.


METHODS
Whole-kidney and single-nephron haemodynamics and function were measured. Glomerular capillary pressure was estimated from tubular stop-flow pressure measurements.


RESULTS
Blood pressure (P < 0.001), renal blood flow (RBF, P < 0.05) and glomerular filtration rate (P < 0.01) were increased following ACTH treatment compared with sham. There were no differences in either total renal, or pre- or post-glomerular vascular resistances, but stop-flow-estimated glomerular capillary pressure was elevated (P < 0.001) as was single-nephron glomerular filtration rate (SNGFR) (P < 0.001) and single-nephron blood flow (P < 0.01 ) in the ACTH- compared to the sham-treated rats. L-NNA treatment increased blood pressure by a similar extent in both ACTH- and sham-treated rats, but reduced RBF (P < 0.05) and glomerular filtration rate (GFR) (P < 0.05) more in the ACTH group; similar changes were seen in single-nephron values. L-NNA increased pre- and post-glomerular resistances to a greater extent in the ACTH group.


CONCLUSIONS
ACTH-induced hypertension produced glomerular hypertension and hyperfiltration, which may be due to nitric oxide-related vasodilatation of the renal vasculature.
Denton
K M
KM
Department of Physiology, Monash University, Melbourne, Australia. k.denton@med.monash.edu.au
Li
M
M
Anderson
W P
WP
Whitworth
J A
JA
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D005919:Glomerular Filtration Rate / Q000187:drug effects*; D006439:Hemodynamics / Q000187:drug effects; D006973:Hypertension / Q000139:chemically induced*; D007678:Kidney Glomerulus / Q000503:physiopathology*; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D019335:Nitroarginine; D009569:Nitric Oxide; D000324:Adrenocorticotropic Hormone