Influence of feeding, blood sampling method and type of anaesthesia on renal function parameters in the normal laboratory rat.

With sophisticated experiments it is necessary to handle laboratory animals many times. To determine the effect of minor handling a series of experiments was performed to measure the impact of fasting, anaesthesia, blood collection method and serum creatinine analysis on renal function. Simple clinical methods to measure renal function parameters such as diuresis, urinary osmolality, urinary creatinine excretion and serum creatinine were used. During fasting a significant increase (P < 0.01) in diuresis and a significant decrease (P < 0.01) in urinary osmolality were noted. Fasting and anaesthesia have the additional effect of significantly decreasing (P < 0.05) urinary creatinine excretion. Blood sampling method also has a significant impact on serum creatinine: venous sampling causes false-positive differences compared with simultaneous arterial sampling.