TC-99M-CYSTINE, A RENAL-FUNCTION AND IMAGING AGENT - A COMPARATIVE-STUDY IN DOG WITH I-131 HIPPURATE AND TC-99M-GLUCOHEPTONATE TO EVALUATE ITS FUNCTIONAL AND IMAGING CHARACTERISTICS

99Tc(m)-cystine, which has been proposed as a renal radiopharmaceutica l for evaluating renal morphology and function in a single experiment, is compared with I-131-orthoiodohippurate (OIH) with respect to its r enal clearance and extraction parameters and with 99Tc(m)-glucoheptona te (GHA) regarding its imaging characteristics. In spite of its compar able renal accumulation with I-131-OIH, its clearance (10.1 +/- 1.0 ml min-1 kg-1) was lower than that of I-131-OIH (21.5 +/- 0.9 ml min-1 k g-1) but was higher than that of I-125-iothalamate (5.4 +/- 0.6 ml min -1 kg-1). Extraction efficiencies of 99Tc(m)-cystine, I-131-OIH and I- 125-iothalamate were 39 +/- 5, 64 +/- 4 and 27 +/- 3, respectively. Th e glomerular filtration components of 99Tc(m)-cystine and I-131-OIH we re 26 and 16% of their respective clearances. In probenecid-treated an imals the clearance of both agents was affected to a similar extent an d fell to half of their respective control values, whereas tubular sec retory components were found to be 19 and 31% of the controls. The kid ney images obtained with 99Tc(m)-cystine were superior to those obtain ed with 99Tc(m)-GHA at different time points. Therefore, considering b oth renal function and imaging properties of 99Tc(m)-cystine it appear s that this radiopharmaceutical offers some definite advantages over t he currently available renal agents and commands further study.