AJP - Renal Physiology, Vol 256, Issue 1 100-F106, Copyright © 1989 by American Physiological Society
Tubular handling of neurotensin in the rat kidney as studied by micropuncture and HPLC
T. Bjerke, E. I. Christensen and N. Boye
Department of Cell Biology, University of Aarhus, Denmark.
Micropuncture studies were performed to assess the reabsorption and
metabolism of the vasoactive peptide neurotensin (NT) in individual nephron
segments and compare it to the handling of the closely related peptide
bradykinin (BK). Rat proximal and distal convoluted tubules were
microinfused with [3H]NT or [3H]BK. In a second set of experiments, [3H]NT
and its metabolites in the ureteral urine were separated and characterized
using high-performance liquid chromatography (HPLC) technique. The urinary
recovery of 3H-labeled material was 31% when proximal tubules were
microinfused with [3H]NT and 94% when distal tubules were infused. For
proximal tubules the label recovered in the ureteral urine consisted
exclusively of metabolites of NT and appeared as tyrosine, NT1-11, probably
NT9-13, and two uncharacterized products. For distal tubules, 9%
chromatographed as intact NT in the urine and except for the proportion the
metabolites were almost identical to those found when proximal tubules were
microinfused. Following microinfusion of [3H]BK into proximal tubules, the
urinary recovery of 3H-labeled material was 19%. There was no correlation
between fractional reabsorption of 3H-labeled material and proximal tubular
length when [3H]NT or [3H]BK was microinfused. In vitro incubation studies
with rat ureteral urine showed extensive degradation of NT yielding
tyrosine, NT1-6, probably NT9-13, NT, and two uncharacterized products. In
contrast, there was no detectable breakdown of BK over a 32-min period.
Finally, [3H]NT was incubated in rat serum, and these experiments also
showed degradation of the peptide but not to the extent as when incubated
in ureteral urine.(ABSTRACT TRUNCATED AT 250 WORDS)
