THE EXCRETION OF INULIN BY THE DOG

Abstract

Studies on the excretion of inulin, in relation to glomerular filtration, similar to those made by Shannon and Smith on man, are here reported on the dog. The rate of inulin excretion in the dog is directly proportional to plasma concn. between values of 53 and 565 mgm. %. The intraven. administration of inulin did not affect the urea, xylose or creatinine clearances. In 42 comparisons on 8 dogs, the mean ratio of the simultaneous creatinine and inulin clearances was 0.994 with a standard deviation of 0.034, and max. variations of +0.086 and[long dash]0.064. The xylose clearance in the normal dog at moderate to high urine flows was less than the simultaneous inulin clearance, the mean xylose/inu-lin ratio being 0.734, with a standard deviation of 0.022. Under phlorizin the glucose clearance rose to the level of the creatinine and inulin clearances, the equality of which was maintained, while the xylose clearance was raised to within 10% of the inulin clearance. It is concluded that inulin is not secreted by the renal tubuleg, and it appears unlikely that there is any active or passive reabsorption of this substance, the inulin clearance therefore approximating very closely to the glomerular clearance.