Renal catabolism of 125I-glicentin.
The renal catabolism of 125I-glicentin has been studied in vivo by the disappearance of this peptide from the plasma of bilaterally nephrectomized, ureteral-ligated, or normal rats and by using tubular microinfusion techniques. In addition the catabolism of glicentin by the isolated, perfused kidney has been studied. Results from in vivo studies demonstrated that half-disappearance time was lower in control (59.5 +/- 1.8 min) than in bilaterally nephrectomized rats (97.2 +/- 2.6 min), and this value was significantly higher than that of ureteral-ligated animals (83.2 +/- 1.1 min, P less than 0.005). Microinfusion experiments revealed that when 125I-glicentin was injected into the proximal tubule, no trichloroacetic-precipitable radioactivity was recovered in the urine, whereas most of inulin injected was recovered. By contrast most of the 125I-glicentin injected into the distal tubule was recovered in the urine. In isolated kidney experiments, organ clearance rate of 125I-glicentin averaged 0.88 +/- 0.10 ml/min, a value significantly higher than that of glomerular filtration rate (0.72 +/- 0.06 ml/min, P less than 0.005, paired data), and both parameters showed a close linear relationship (r = 0.90). Urinary clearance of glicentin was negligible. These results demonstrate that the kidney plays a major role in the catabolism of glicentin, mainly by glomerular filtration and tubular catabolism. The site of tubular catabolism appears to be the proximal tubule. Peritubular uptake was minimal.
J M
JM
López-Novoa
J C
JC
Santos
L M
LM
Villamediana
F J
FJ
Garrote
L
L
Thim
A J
AJ
Moody
I
I
Valverde
D000818:Animals; D011232:Chemical Precipitation; D002850:Chromatography, Gel; D005919:Glomerular Filtration Rate; D005934:Glucagon / Q000378:metabolism*; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D007668:Kidney / Q000378:metabolism*; D007686:Kidney Tubules, Distal / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D007700:Kinetics; D008026:Ligation; D008657:Metabolic Clearance Rate; D009392:Nephrectomy; D010477:Perfusion; D052336:Proglucagon; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014513:Ureter / Q000502:physiology
D007457:Iodine Radioisotopes; D011498:Protein Precursors; D052336:Proglucagon; D005934:Glucagon