Method for the microassay of endogenous creatinine in blood and urine of small murid rodents

The estimation of endogenous creatinine clearance yields information useful to the renal physiologist without the need to introduce a marker compound. The method has been limited in its application to mammalian species of bodyweight 200 g and above due to the blood sample size required. A modification is described whereby this procedure may be applied to animals of bodyweight as low as 25 g. Use of this microassay is illustrated in an investigation of the effect of salt and urea loading on renal function in an Australian desert mouse, Notomys alexis.