Plasma clearance and tissue distribution of radiolabeled leptin in the chicken.
Leptin is an adipose and liver tissue-derived secreted protein in chickens that has been implicated in the regulation of food intake and whole-body energy balance. In this study, the metabolic clearance and tissue uptake of leptin were examined in the chicken (Gallus gallus). Four-week-old broiler males were infused with (125)I-labeled mouse leptin. Chromatography of radiolabeled leptin in plasma produced two peaks, one at 16 kDa (free leptin) and a free iodine peak. No leptin binding protein in blood was detected. Leptin was cleared with a half-life estimate of 23 min. In order to investigate the tissue distribution and uptake of radiolabeled leptin, multiple tissues were removed from infused birds at 15 and 240 min post-infusion, and trichloroacetic acid (TCA)-precipitable radioactivity was determined. The amounts of radioactivity at 15 min post-infusion in the tissues in rank order were: kidney, testis, lung, spleen, heart, liver, small and large intestine, gizzard, pancreas, bursa, leg and breast muscle, adrenals, and brain. A slightly different pattern of distribution was observed at 240 min post-infusion. We conclude from these studies that unlike mammals, no circulating leptin binding protein is present in chickens. Leptin is metabolized and cleared very rapidly from blood by the kidney.
McMurtry
John P
JP
Growth Biology Laboratory, U.S. Department of Agriculture, Agricultural Research Service, ANRI, GBL, Bldg. 200, Rm. 217, BARC-East, 10300 Baltimore Avenue, Beltsville, MD 20705-2350, USA. mcmurtry@anri.barc.usda.gov
Ashwell
Christopher M
CM
Brocht
Donna M
DM
Caperna
Thomas J
TJ
D000818:Animals; D002645:Chickens; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D020738:Leptin / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D011956:Receptors, Cell Surface / Q000097:blood; D054411:Receptors, Leptin; D014018:Tissue Distribution; D014238:Trichloroacetic Acid / Q000032:analysis / Q000378:metabolism
D007457:Iodine Radioisotopes; D020738:Leptin; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; C515447:leptin receptor, mouse; D014238:Trichloroacetic Acid