99Tcm-cystine, a renal function and imaging agent: a comparative study in dog with 131I-hippurate and 99Tcm-glucoheptonate to evaluate its functional and imaging characteristics.

99Tcm-cystine, which has been proposed as a renal radiopharmaceutical for evaluating renal morphology and function in a single experiment, is compared with 131I-orthoiodohippurate (OIH) with respect to its renal clearance and extraction parameters and with 99Tcm-glucoheptonate (GHA) regarding its imaging characteristics. In spite of its comparable renal accumulation with 131I-OIH, its clearance (10.1 +/- 1.0 ml min-1 kg-1) was lower than that of 131I-OIH (21.5 +/- 0.9 ml min-1 kg-1) but was higher than that of 125I-iothalamate (5.4 +/- 0.6 ml min-1 kg-1). Extraction efficiencies of 99Tcm-cystine, 131I-OIH and 125I-iothalamate were 39 +/- 5, 64 +/- 4 and 27 +/- 3, respectively. The glomerular filtration components of 99Tcm-cystine and 131I-OIH were 26 and 16% of their respective clearances. In probenecid-treated animals the clearance of both agents was affected to a similar extent and fell to half of their respective control values, whereas tubular secretory components were found to be 19 and 31% of the controls. The kidney images obtained with 99Tcm-cystine were superior to those obtained with 99Tcm-GHA at different time points. Therefore, considering both renal function and imaging properties of 99Tcm-cystine it appears that this radiopharmaceutical offers some definite advantages over the currently available renal agents and commands further study.