Fig. 3. Serum glucose (left) and serum osmolality (right) before, during, and after food and water deprivation (FWD). Data are given as mean, minimum (min), and maximum (max) values. Normal range for glucose: 3.3-6.6 mmol/l; normal range for osmolality: 275-295 mOsm/l; Pw3: Pw value resulted from the comparison between day 0 and day 3.
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Fig. 4. Serum concentrations of A Na+ (normal range 135-152 mmol/l); B K+ (normal range 3.5-5.5 mmol/l); C Cl- (normal range 95-107 mmol/l); D urea (normal range 1.7-8 mmol/l) before, during, and after food and water deprivation (FWD). Data are given as mean, minimum (min), and maximum (max) values.
Creatinine Levels and Creatinine Clearance
In order to evaluate indicative factors for renal function, we determined the levels of serum creatinine and creatinine clearance. Serum creatinine increased slightly, reaching the highest mean value of 8 μmol/l (0.96 mg/dl) on day 5. Interestingly, there was a considerable increase in creatinine clearance. The mean values were 150 ml/min on day 0 (before FWD), 229 ml/min (+53%) on day 1, 222 ml/min (+49%) on day 2, 181 ml/min (+21%) on day 3, 250 ml/min (+67%) on day 4, and 207 ml/min (+38%) on day 5. 3 days after FWD (day 8), the creatinine clearance was diminished to 125 ml/min (-17%) (fig. 5). Although statically significant, the creatinine increase was not substantial. On the other hand, the increase of creatinine clearance was impressive and without exception. The different magnitude of its increase among the participants could not be correlated with BMI or age.