AJP - Renal Physiology, Vol 248, Issue 3 404-F412, Copyright © 1985 by American Physiological Society
Reabsorption and secretion of alpha-ketoglutarate along the rat nephron: a micropuncture study
B. Ferrier, M. Martin and G. Baverel
The transport of alpha-ketoglutarate (alpha-KG) across the luminal membrane
of the rat nephron was studied by micropuncture and microassay techniques.
In normal and acidotic rats, approximately 75% of the filtered alpha-KG was
reabsorbed in the proximal tubule and 20% in the pars recta and/or loop of
Henle at endogenous plasma concentration of alpha-KG. A progressive
elevation to steady-state levels of plasma alpha-KG resulted in a
progressive reduction of the fractional reabsorption of alpha-KG in the
proximal tubule as well as in a progressive increase in the fractional
reabsorption of alpha-KG in the pars recta and/or loop of Henle. At plasma
alpha-KG concentration 20-40 times above normal, reabsorption of alpha-KG
was found to be limited by a maximal tubular capacity. In alkalotic rats,
net secretion of alpha-KG in the early proximal convoluted tubule, net
reabsorption in the remainder of the proximal convoluted tubule, and net
secretion in the pars recta and/or loop of Henle were observed. These
micropuncture data indicate that, depending on the acid-base conditions,
net reabsorption or net secretion of alpha-KG may occur in at least two
distinct sites along the rat nephron.
