^99mTc‐MAG3 kinetics in the normal pig. A comparison to ¹³¹I‐OIH and ¹²⁵I‐iothalamate after single injection and during continuous infusion

Abstract

An invasive comparative study of some pharmacokinetic aspects of 99mTcmercaptoacetyltriglycine (MAG& 1311-orthoiodohippurate (OIH), and 1251-iothalamate (iothalamate) was performed in six pigs 0-150 min after a simultaneous single injection (SI) and during a subsequent 90 rnin of continuous infusion ((21). The total plasma clearance and the renal clearance of MAG3 were about 75% that of OIH. The renal clearance of MAG3 was about 2% times the glomerular filtration rate. The distribution volume of MAG3 was 71% that of iothalamate and only 47% that of OIH. There was a significant hepatic plasma clearance of MAG3 of 5-9 ml rnin-l and 3.9% of the injected dose was excreted in the bile. HPLC analysis revealed that technetium was excreted in urine and bile mainly labelled to MAG3. The average red blood cell (RBC) binding after single injectiodduring continuous infusion was 1.0%/2.3% for MAG3, 13.5%/9.0% for OIH, and 3.1%/5.3% for iothalamate. The binding of OIH to RBC in arterial blood increased from 8% at 1 min post-injection to 21% at 150 rnin post-injection. The RBC binding was higher in the renal vein, indicatingincomplete back diffusion from RBC to plasma. The protein binding was 90% for MAG3,49% for OIH and 16% for iothalamate. The renal plasma extraction of MAG3 was constant but significantly smaller after SI (0.54) than during CI (0.62). Following SI, the renal plasma extraction of OIH decreased continuously from 0.85 to 0.52,3-150 min post-injection. On the average there was no significant difference in renal plasma extraction after SI and during CI of either OIH (0-72 versus 0.77) or iothalamate (0-26 versus 0.27). It is concluded that MAG3 is preferential to OIH as a tracer for renal function studies using a single injection technique mainly due to the constant renal extraction of MAG3.

Noninvasive measurement of tracer extraction efficiency in tissue, illustrated with Tc-99m-MAG3

“…Renal E for Tc-99m-MAG3 has been found to vary in experimental animals between 54% in pigs [5] and >80% in rodents [6,7]. E in humans, measured from renal vein catheterisation in five patients, was reported to be 55% [8].…”

Noninvasive assessment of renal dynamics and pH in a unilateral ureter obstruction model using DCE MR‐CEST urography

“…Urographic contrast media such as iopamidol and 99m Tc‐MAG3 are primarily filtered through the glomerulus and primarily not reabsorbed or secreted in the renal tubule, 6,45 therefore, it is possible to monitor their transit through vascular and tubular compartments through DCE‐CT, MRI and renal scintigraphy. The resulting contrast kinetics provides a measure of renal function.…”

Technetium‐99m‐MAG3 and technetium‐99m‐DTPA: Renal clearance measured by the constant infusion technique – Old news?

“…Several studies have shown that 99m Tc‐MAG 3 and 123 I‐OIH share characteristics of renal uptake and elimination, even in patients with impaired renal function (Bubeck et al, 1990; Rehling et al, 1995; Russell & Dubovsky, 1999; Russell et al, 1988), whereas others indicate that 99m Tc‐MAG 3 has a larger protein binding, slower plasma Cl, larger extraction efficiency in the tubules and a higher excretion through the bile than 123 I‐OIH (Bubeck et al, 1990; Rehling et al, 1995). A review by Itoh et al stated that the plasma Cl ratio of 99m Tc‐MAG 3 / 123 I‐OIH was 0.44–1.07, and protein binding for 99m Tc‐MAG 3 was higher (75–90%) compared to that of 123 I‐OIH (53–74%) (Itoh, 2001).…”