Secondary effect parameters will be the following: GFR, K+ excretion, creatinine excretion, urea excretion, as well as urinary concentrations of aquaporin 2 (AQP2), PGE2, AVP, URO, Na-transporter protein, concentration of renin, ANG II, ALDO, ANP, in plasma, prior to and after the administration of indomethacin.