Use of the double-isotope single-injection method for estimating renal function in normal cross-bred swine

The double-isotope single-injection method to estimate renal function which utilizes the radiolabeled chemicals [131I]sodium iodohippurate and [125I]sodium iothalamate was evaluated in swine. A total of 46 normal, cross-bred swine were used to determine the applicability of this method for measuring the glomerular filtration rate and effective renal plasma flow. The mean glomerular filtration rate in pigs was determined to be 5.33 +/- 0.82 ml/kg of body weight/minute for [125I]sodium iothalamate with a biological half-life (T 1/2) of 39.18 +/- 7.44 minutes. The mean effective renal plasma flow was determined to be 19.25 +/- 3.12 ml/kg of body weight/minute for [313I]sodium iodohippurate, with a T 1/2 of 18.45 +/- 1.74 minutes. These values are more closely related to the glomerular filtration and effective renal plasma flow values reported for dogs and cats than they are to values reported for man. The method is rapid and reliable; results are available 6 to 8 hours after the experiment. This method is advantageous when information about renal function variables is a prerequisite to pharmacokinetic or toxicologic studies.