Sildenafil reduces polyuria in rats with lithium-induced NDI

Sanches TR, Volpini RA, Massola Shimizu MH, de Bragan a AC, Oshiro-Monreal F, Seguro AC, Andrade L. Sildenafil reduces polyuria in rats with lithium-induced NDI. Am J Physiol Renal Physiol 302: F216-F225, 2012. First published October 12, 2011; doi:10.1152/ajprenal.00439.2010.-Lithium (Li)-treated patients often develop urinary concentrating defect and polyuria, a condition known as nephrogenic diabetes insipidus (NDI). In a rat model of Li-induced NDI, we studied the effect that sildenafil (Sil), a phosphodiesterase 5 (PDE5) inhibitor, has on renal expression of aquaporin-2 (AQP2), urea transporter UT-A1, Na(+)/H(+) exchanger 3 (NHE3), Na(+)-K(+)-2Cl(-) cotransporter (NKCC2), epithelial Na channel (ENaC; alpha-, beta-, and gamma-subunits), endothelial nitric oxide synthase (eNOS), and inducible nitric oxide synthase. We also evaluated cGMP levels in medullary collecting duct cells in suspension. For 4 wk, Wistar rats received Li (40 mmol/kg food) or no treatment (control), some receiving, in weeks 2-4, Sil (200 mg/kg food) or Li and Sil (Li+Sil). In Li+Sil rats, urine output and free water clearance were markedly lower, whereas urinary osmolality was higher, than in Li rats. The cGMP levels in the suspensions of medullary collecting duct cells were markedly higher in the Li+Sil and Sil groups than in the control and Li groups. Semiquantitative immunoblotting revealed the following: in Li+Sil rats, AQP2 expression was partially normalized, whereas that of UT-A1, gamma-ENaC, and eNOS was completely normalized; and expression of NKCC2 and NHE3 was significantly higher in Li rats than in controls. Inulin clearance was normal in all groups. Mean arterial pressure and plasma arginine vasopressin did not differ among the groups. Sil completely reversed the Li-induced increase in renal vascular resistance. We conclude that, in experimental Li-induced NDI, Sil reduces polyuria, increases urinary osmolality, and decreases free water clearance via upregulation of renal AQP2 and UT-A1.

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP

Foundation for the Support of Research in the State of Sao Paulo)

Foundation for the Support of Research in the State of Sao Paulo)

Laboratorios de Investigacao Medica (LIMs

Laboratorios de Investigacao Medica (LIMs

Medical Investigation Laboratories) of the Faculdade de Medicina da Universidade de Sao Paulo (FMUSP

Medical Investigation Laboratories) of the Faculdade de Medicina da Universidade de Sao Paulo (FMUSP

University of Sao Paulo School of Medicine) Hospital das Clinicas

University of Sao Paulo School of Medicine) Hospital das Clinicas

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq

National Council for Scientific and Technological Development

National Council for Scientific and Technological Development) [134318/2006-4, 309430/2006-7, 302835/2009-1]