ENDOGENOUS CREATININE CLEARANCE IN THE RAT - STRAIN VARIATION

The clearance of endogenous creatinine was examined in five strains of rats (Wistar, Wistar Kyoto, Spontaneously Hypertensive, Rats, Biobree ding/ Worcester diabetic prone and diabetic resistant rats). Creatinin e clearance was compared with inulin clearance as the standard. Condit ions for clearance measurements were also varied (anesthesia with cons tant infusion, overnight collection of urine, fed vs. unfed state, sin gle-injection technique). The clearance of creatinine adequately refle cts the glomerular filtration rate in three strains (Wistar, Wistar-Ky oto and the Spontaneously Hypertensive Rat). In the two strains of the Biobreeding/ Worcester rat creatinine clearance is consistently lower than the inulin clearance. When creatinine clearance is measured from an overnight collection of urine with food withheld it is always lowe r than when food is present. This clearance should always be validated by comparison with inulin clearance measured simultaneously or under comparable conditions. The ease with which endogenous creatinine clear ance can be measured makes it a reasonable method when large numbers o f repeated determinations of glomerular filtration rate are required.