Increased cGMP phosphodiesterase activity mediates renal resistance to ANP in rats with bile duct ligation

• Published in: Kidney international Vol. 59; no. 4; pp. 1264 - 1273
• Main Authors: Ni, Xi-Ping, Safai, Massy, Gardner, David G., Humphreys, Michael H.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01-04-2001; Nature Publishing; Elsevier Limited
• Subjects: 3',5'-Cyclic-GMP Phosphodiesterases - antagonists & inhibitors; 3',5'-Cyclic-GMP Phosphodiesterases - metabolism; Allopurinol - analogs & derivatives; Allopurinol - pharmacology; Animals; Atrial Natriuretic Factor - pharmacology; atrial natriuretic peptide; Biological and medical sciences; chronic liver disease; Common Bile Duct; Cyclic GMP - metabolism; Cyclic Nucleotide Phosphodiesterases, Type 5; Drug Resistance; GMP-specific phosphodiesterase; Hydrolysis - drug effects; inner medullary collecting duct; Kidney - cytology; Kidney - drug effects; Kidneys; Ligation; Male; Medical sciences; Natriuresis - drug effects; Nephrology. Urinary tract diseases; Phosphodiesterase Inhibitors - pharmacology; Plasma Substitutes - pharmacology; Purinones - pharmacology; Rats; Rats, Sprague-Dawley; Sodium Chloride - pharmacology; sodium excretion; Urinary system involvement in other diseases. Miscellaneous; chronic liver disease; atrial natriuretic peptide; sodium excretion; GMP-specific phosphodiesterase; inner medullary collecting duct; Kidney disease; Biliary tract; Urinary system disease; Rat; Chemical resistance; Enzyme; Pathogenesis; Rodentia; Metabolic diseases; 3',5'-GMP; Esterases; Atrial natriuretic peptide; Phosphoric diester hydrolases; Biliary tract disease; Obstruction; Vertebrata; Experimental disease; Mammalia; Enzymatic activity; Animal; Digestive diseases; Hydrolases; Complication; Phosphodiesterase I
• ISSN: 0085-2538; 1523-1755
• DOI: 10.1046/j.1523-1755.2001.0590041264.x

Increased cGMP phosphodiesterase activity mediates renal resistance to ANP in rats with bile duct ligation.
Liver disease resulting from common bile duct ligation (CBDL) causes abnormal sodium metabolism that is manifested by resistance to the natriuretic action of atrial natriuretic peptide (ANP). This resistance is corrected both in vitro and in vivo by zaprinast, a selective inhibitor of a guanosine cyclic-3′-5′-monophosphate (cGMP)-specific phosphodiesterase (PDE5). Several other PDEs with affinity for cGMP are expressed in kidney and could also be involved in this response.
We measured cGMP hydrolysis in inner medullary collecting duct (IMCD) cell homogenates from kidneys of sham-operated and CBDL rats and quantitated the amount of PDE5 protein by Western blotting and immunoprecipitation studies. We also characterized ANP responsiveness in vivo of kidneys of anesthetized sham and CBDL rats by measuring sodium excretion before and after volume expansion (VE).
Kinetic analysis of PDE5 activity in homogenates of IMCD cells isolated from kidneys of sham-operated rats indicated a Vmax of 85.3 ± 1.7 versus 157 ± 2.9 pmol/mg/min from CBDL rats (P < 0.01), without a difference in Km. Enzyme activity was inhibited competitively by 1,3-dimethyl-6-(2-propoxy-5-methanesulfonylamidophenyl)pyrazol[3,4d]-pyrimidin-4-(5H)-one (DMPPO), a potent and specific inhibitor of PDE5, with an apparent Ki of 4.5 ± 0.7 and 4.9 ± 0.7 nmol/L and an IC50 of 6.1 ± 0.8 and 8.7 ± 0.7 nmol/L in sham and CBDL rats, respectively (P = NS). DMPPO exhibited very poor inhibitory activity against the calcium-calmodulin–dependent PDE1 in IMCD homogenates from sham rats (Ki 1.3 ± 0.1 μmol/L and IC50 1.9 ± 0.2 μmol/L). Western analysis using an antiserum made against bovine lung PDE5 revealed a twofold increase in PDE5 protein in cytosolic extracts from IMCD of CBDL rat kidneys compared with sham-operated controls, and immunoprecipitation studies indicated that the increase in PDE5 protein accounted for the observed increase in cGMP hydrolysis. DMPPO (10 nmol/L) normalized the blunted ANP-dependent cGMP accumulation by IMCD cells from CBDL rats in vitro. Intrarenal infusion of DMPPO (0.5 nmol/min) in CBDL rats corrected both the impaired natriuretic response to VE and the blunted VE-related increase in urinary cGMP excretion from the infused, but not the contralateral kidney.
These results demonstrate that renal resistance to ANP in CBDL rats is accompanied by heightened activity of PDE5, which is due largely to an increase in PDE5 protein. Other PDEs could contribute only a minor part to the enhanced cGMP hydrolysis observed in kidneys of CBDL rats. This PDE5-dependent ANP resistance may represent an important contributor to the sodium retention of liver disease.