AJP - Endocrinology and Metabolism, Vol 247, Issue 6 786-E792, Copyright © 1984 by American Physiological Society
Role of the kidney in metabolism of gonadotropins in rats
D. S. Emmanouel, T. Stavropoulos and A. I. Katz
The role of the kidney in the metabolic disposal of homologous
gonadotropins [renal luteinizing hormone (rLH) and renal
follicle-stimulating hormone (rFSH)] was studied in rats. In analogy with
other protein hormones, renal mechanisms contributed importantly to their
metabolic clearance rates (MCR), which were profoundly and comparably
decreased following nephrectomy (by 94 and 78% for rLH and rFSH,
respectively). Absolute MCR and renal organ clearance rates of
gonadotropins were, however, markedly lower and urinary clearance rates
proportionally higher than those of nonglycosylated protein hormones
reported previously. Nonetheless, handling of both LH and FSH by the kidney
probably involves, in addition to their excretion in the urine, also
intrarenal degradation because their urinary clearance rates accounted for
at most a third of their respective MCR, considerably less than the
striking reduction of MCR seen after acute renal ablation. Moreover, losses
of LH immunoreactivity across the renal circulation were over and above
those accountable for by urinary excretion alone. Thus, handling of
gonadotropins by the kidney differs from that of nonglycoprotein hormones
both in magnitude and in that it involves, in addition to intrarenal
degradation, also substantial urinary excretion, a pattern that appears to
be representative of the way the kidney disposes of glycoprotein hormones
in general.
