Whole body leptin kinetics and renal metabolism in vivo.
Zeng, Jianbo, Bruce W. Patterson, Samuel Klein, Daniel R. Martin,
Samuel Dagogo-Jack, Wendy M. Kohrt, Steven B. Miller, Michael Landt.
Departments of Pathology, Medicine and Pediatrics, Washington
University, School of Medicine, St Louis, MO
APStracts 4:0178E, 1997.
Leptin metabolism was investigated in male Sprague-Dawley rats, using
125I-leptin plasma kinetic and arterio-venous balance studies. When
conscious rats received bolus venous injections of 125I-leptin,
intact (precipitable) leptin quickly disappeared from circulation in
a bi-exponential manner during the two-hour experimental period.
After substantial delay, most of the injected radioactivity appeared
in the urine. The data were described by a two-compartment model,
which postulated that plasma leptin exchanged with a non-plasma pool,
and that all of the tracer cleared from plasma appeared in urine or
in a degraded form in plasma. The half-life of leptin was 9.4 _+/-_
3.0 min, and the leptin production rate was 3.6 +/-_ 1.2 ng per 100 g
fat per min. The left kidney extracted 21_+/-_ 1.5% of intact
arterial 125I-leptin five minutes after femoral venous injection.
Endogenous arterial leptin was reduced 21 +/-_ 8% and 18 _+/-_ 12% in
simultaneously sampled left and right renal veins respectively. Renal
elimination appears to be the major elimination mechanism for leptin
in normal rats and the kinetic studies suggest that uptake of leptin
by renal tissue rather than glomerular filtration is the predominant
elimination mechanism.
Received 27 May 1997; accepted in final form 7 August 1997.
APS Manuscript Number E241-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 27 August 1997