Aquaporin-1 expression in proximal tubule epithelial cells of human kidneyis regulated by hyperosmolarity and contrast agents

Primary cells of renal proximal tubule epithelium (S1 segment) of human kid ney (HRPTE cells) upregulate aquaporin-1 (AQP-1) expression in response to hyperosmolarity. NaCl and D(+)-raffinose increased (2-2.5 fold) AQP-1 expre ssion when medium osmolarity was 400 and 500 mOsm/kg.H2O. Urea did not have this effect. Unlike our previous findings with mIMCD-3 cells, vasopressin (10(-8)M) did not affect AQP-1 expression in HRPTE cells in isosmolar or Na Cl-enriched hyperosmolar conditions. Furthermore, HRPTE cells increased (3- 4 fold) AQP-1 expression when exposed to hyperosmolar Reno-60 and Hypaque-7 6 (diatrizoates, ionic) contrast agents at 400 and 500 mOsm/kg.H2O. Isosmol ar (290 mOsm/kg H2O) Visipaque (iodixanol, non-ionic) at 10% (v/v) concentr ations also increased AQP-1 expression, and 25% v/v of Visipaque rendered m orphological alterations of HRPTE cells and a 3-fold increase in AQP-1 expr ession after 24h exposure. Finally, semi-quantitative RT-PCR of HRPTE cells subjected to various isosmolar or hyperosmolar conditions demonstrated up- regulation of AQP-1 mRNA and protein levels. Our results suggest AQP-1 upre gulation in HRPTE cells exposed to environmental stresses such as hyperosmo larity and high doses of isosmolar contrast agents. (C) 1999 Academic Press .