The kidneys have numerous salt and water channels and play a major role in the regulation of sodium and water. We do not know how these channels work in certain water and sodium accumulating medical conditions.

The purpose of this study is to identify and measure the activity in the water and sodium channels by measuring urine biomarkers/proteins in young healthy subjects.

25 healthy subjects from age 18-45 are recruited.

Subjects will be examined on three examination days. Four days prior to the examination days the subjects will consume a standard diet based on the amount of sodium and calories.

On the examination day subjects are randomised to an infusion with either isotonic saline 23 ml/kg, hypertonic saline 7 ml/kg or glucose 23 ml/kg for a period of 50 minutes.

Renal function is measured by renal clearance of 51Cr-EDTA, urinary sodium, potassium and creatinine.

Urinary NCC, NKCC and ENAC will be measured to evaluate the activity of sodium channels in the nephron.

Inclusion Criteria:

• healthy males and females
• age 18-45
• BMI range 18,5-30,0 kg/m2

Exclusion Criteria:

• hypertension (ie ambulatory BP >130 mmHg systolic or/and >80 mmHg diastolic)
• history or clinical significant signs of heart, lung, liver, kidney, endocrine, brain or neoplastic disease.
• alcohol abuse
• drug abuse
• smoking
• pregnancy or nursing
• blood donation within a month prior to examination
• Medical treatment apart from oral contraception