title: Clearance and renal extraction of technetium-99m-L,L-ethylenedicysteine, I-131-ortho-iodohippurate and I-125-iothalamate in pigs.
abstract: 99mTc-L,L-ethylenedicysteine (99mTc-EC) has been proposed as a 99mTc-labelled alternative to radio-iodinated ortho-iodohippurate (OIH) for renal imaging and evaluation of renal function. The kinetics of this new renal function agent were studied by a single-injection plasma clearance technique in pigs. 99mTc-EC, 131I-OIH and 125I-iothalamate were injected and the plasma concentration of the three tracers was followed for 240 min. Renal, hepatic and total plasma clearance were calculated. There was no difference between the renal plasma clearance of 99mTc-EC and 131I-OIH (175 +/- 9 versus 178 +/- 8 ml min-1, P = 0.43), whereas the difference between the total plasma clearance of 99mTc-EC and 131I-OIH was highly significant (268 +/- 16 versus 185 +/- 9 ml min-1, P = 0.0001). 99mTc-EC had a significant hepatic clearance of 83 +/- 10 ml min-1 whereas the hepatic clearance of 131I-OIH was negligible. Renal plasma extraction of both 99mTc-EC and 131I-OIH decreased significantly between 2 and 240 min post-injection from 0.85 to 0.45% for 99mTc-EC and from 0.93 to 0.57% for 131I-OIH. Red blood cell binding of 99mTc-EC and 131I-OIH was 6.1% and 20%, respectively. The protein binding of 99mTc-EC and 131I-OIH was 32% for both tracers. We conclude that 99mTc-EC is not a suitable tracer for measuring renal function by the single-injection plasma clearance technique in pigs. This is due to a decreasing renal extraction and a significant hepatic clearance.
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, Aarhus University Hospital, Skejby Section, Denmark.
authors.forename: S S
authors.initials: SS
authors.lastname: Nielsen
authors.forename: E U
authors.initials: EU
authors.lastname: Poulsen
authors.forename: J
authors.initials: J
authors.lastname: Marqversen
authors.forename: L E
authors.initials: LE
authors.lastname: Nielsen
authors.forename: T
authors.initials: T
authors.lastname: Bacher
authors.forename: M
authors.initials: M
authors.lastname: Rehling
mesh_terms: D000818:Animals; D001646:Bile / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003287:Contrast Media / Q000493:pharmacokinetics*; D003545:Cysteine / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics / Q000652:urine; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D007465:Iodohippuric Acid / Q000493:pharmacokinetics*; D007483:Iothalamic Acid / Q000493:pharmacokinetics*; D007668:Kidney / Q000378:metabolism / Q000502:physiology*; D016014:Linear Models; D008099:Liver / Q000378:metabolism; D008657:Metabolic Clearance Rate / Q000502:physiology; D015609:Organotechnetium Compounds / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D019275:Radiopharmaceuticals / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D013552:Swine
chemical_list: D003287:Contrast Media; D007457:Iodine Radioisotopes; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C073806:technetium Tc 99m-ethylenedicysteine; D007465:Iodohippuric Acid; D007483:Iothalamic Acid; D003545:Cysteine