title: Reabsorption and secretion of alpha-ketoglutarate along the rat nephron: a micropuncture study.
abstract: 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.
mesh_terms: D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000378:metabolism; D000471:Alkalosis / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D005919:Glomerular Filtration Rate; D007656:Ketoglutaric Acids / Q000097:blood / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism; D008297:Male; D009399:Nephrons / Q000378:metabolism*; D011677:Punctures; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D007656:Ketoglutaric Acids