The ability to concentrate and dilute urine is primarily regulated via vasopressin (AVP) dependent Aquaporin-2 water channels (AQP2 channels) in the kidney's collecting duct. Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder, characterized by the formation of cyst in the kidneys, causing gradual renal function-loss. Previous studies indicate that ADPKD patients have decreased urine concentration, higher plasma osmolality, and plasma AVP levels compared to healthy controls. Previous studies also indicate that ADPKD patients' dysregulated AVP is an important factor for the pathogenesis and progression of the disease. It is unclear whether ADPKD patients' ability to concentrate and dilute urine are different from those of other cause of chronic renal disease to the same degree. It is also unclear, what mechanisms cause the decreased ability to concentrate and dilute urine in chronic renal disease patients. The purpose of this trial is to investigate the difference in renal function during concentration and dilution test in a case-control, randomized, cross-examination study with ADKPD patients or other cause of chronic renal disease compared to healthy volunteers.

The aim is to measure the difference in renal function, including kidney tubular function, blood pressure and vasoactive hormones in patients with Autosomal dominant polycystic kidney disease (ADPKD) or other chronic renal disease compared to healthy volunteers, during concentration and dilution test.

Inclusion Criteria:

• ADPKD patients: -age >18 years, diagnosis with ADPKD, informed consent, contraception for fertile women
• Patients with chronic kidney disease: age >18 years, diagnosis with chronic kidney disease other then ADPKD, informed consent, contraception for fertile women
• Healthy volunteers: age >18 years, healthy, informed consent, contraception for fertile women

Exclusion Criteria:

• ADPKD patients: Renal transplantation, operation in the kidney, Diabetes mellitus, neoplastic conditions, pregnancy, breastfeeding, unwillingness to participate, intolerance towards urine dilution or urine concentration test, alcohol or medical abuse, BP >170/110 despite regulation, unacceptable side effects to background medication (antihypertensive medicine) during the trial.
• Patients with chronic kidney disease: Renal transplantation, operation in the kidney, Diabetes mellitus, medullary cystic kidney disease, lithium nephropathy, neoplastic conditions, pregnancy, nursing, unwillingness to participate, intolerance towards urine dilution or urine concentration test, alcohol or medical abuse, BP >170/110 despite regulation, unacceptable side effects to background medication (antihypertensive medicine) during the trial.
• Healthy volunteers: Arterial hypertension, significant clinical signs of heart, lungs, liver, kidneys, endocrine, brain or neoplastic disorders, alcohol or drug abuse, medical treatment, smoking, pregnancy or breastfeeding, smoking, clinically significant abnormal findings in blood, urine tests or electrocardiogram, blood donation within the last month before the examination date in the first trial sequence, intolerance to or unacceptable side effects of urine concentration and urine dilution test