Glomerular filtration and tubular secretion of MAG-3 in the rat kidney

Journal Article · Fri Dec 01 04:00:00 EST 1989 · Journal of Nuclear Medicine; (USA)

OSTI ID:5083688

Mueller-Suur, R M; Mueller-Suur, C ^[1]

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1. Karolinska Institute, Stockholm (Sweden)

Technetium-99m mercaptoacetyltriglycine (MAG-3) has recently been introduced as a new radiopharmaceutical for dynamic renal scintigraphy. To elucidate the mechanism of renal excretion, micropuncture experiments were performed in rat kidneys for direct measurements of glomerular filtration and tubular secretory capacity. Fluid of Bowman space was collected from superficial glomeruli and analyzed for its contents of (99mTc)MAG-3, (125I)hippurate and (3H)inulin during constant infusion of these compounds. The ratio of activity of ultrafiltrate to that of arterial plasma was 0.23 for MAG-3, 0.68 for hippurate and 1.04 for inulin which demonstrates that the filtrated amount of MAG-3 is only 23% of that of inulin, presumably because of higher plasma protein binding which was also measured in vitro and found to be 80 +/- 1.5% for MAG-3 and 32 +/- 2% for (125I)hippurate. Proximal and distal tubules were also micropunctured and their tubular fluid as well as the final urine analyzed for the activity of hippurate and MAG-3. The tubular fluid to plasma ratio values along the nephron and in the final urine were all lower for MAG-3 than for hippurate, indicating a lower secretory capacity. From measurements of whole renal clearance, GFR and plasma protein binding the filtered amount of MAG-3 was 0.26 and of hippurate 0.87 ml/min.g kidney weight (p less than 0.001) and the secreted amount 2.01 and 2.38 ml/min.g kidney weight (p less than 0.05), respectively. We conclude that MAG-3 is predominantly excreted by tubular secretion and that the lower renal clearance of MAG-3 as compared with that of hippurate is a result both of a substantially decreased glomerular filtration and of a lower tubular secretion.

• OSTI ID: 5083688
• Journal Information: Journal of Nuclear Medicine; (USA), Journal Name: Journal of Nuclear Medicine; (USA) Vol. 30:12; ISSN 0161-5505; ISSN JNMEA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CARBOHYDRATES
CLEARANCE
COUNTING TECHNIQUES
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC TECHNIQUES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
EXCRETION
HOURS LIVING RADIOISOTOPES
HYDROGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
INULIN
IODINE 125
IODINE ISOTOPES
ISOMERIC NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KIDNEYS
LABELLED COMPOUNDS
MAMMALS
METABOLISM
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
POLYSACCHARIDES
RADIOISOTOPE SCANNING
RADIOISOTOPES
RADIOPHARMACEUTICALS
RATS
RENAL CLEARANCE
RODENTS
SACCHARIDES
SCINTISCANNING
TECHNETIUM 99
TECHNETIUM ISOTOPES
TRITIUM COMPOUNDS
VERTEBRATES
YEARS LIVING RADIOISOTOPES