Biomaterial Database

Is pyruvate carboxylase involved in the renal tubular reabsorption of bicarbonate? 1980

N R Buist

The co-existence of a hereditary defect of pyruvate carboxylase activity along with proximal renal tubular acidosis in several patients prompted the following theories: (1) Some of the bicarbonate which is normally reabsorbed from the glomerular filtrate is trapped in the mitochondria by pyruvate carboxylase in the conversion of pyruvate to oxaloacetate. The subsequent conversion of oxaloacetate to phosphoenol pyruvate releases CO2 in the cytosol. (2) The trapping of HCO-3 by pyruvate (or other carboxylases) provides an important route for the recovery of filtered HCO-3. (3) The process of trapping HCO-3 from the glomerular filtrate followed by release of CO2 in the cytosol contributes to the apparently high RQ of kidney, since the CO2 does not originate from a metabolic fuel. (4) Lactate and possibly other fuels are actively taken up by the kidney and are used as energy sources. Diversion of lactate for gluconeogenesis may contribute to the "excess substrate uptake" phenomenon. (5) It is possible that some of the glucose which is synthesized in the cortex is used for glycolysis in the medulla. Conversely, lactate produced in the medulla may be available to the cortex for bicarbonate trapping and thus for gluconeogenesis.

UI	MeSH Term	Description	Entries
D007684	Kidney Tubules	Long convoluted tubules in the nephrons. They collect filtrate from blood passing through the KIDNEY GLOMERULUS and process this filtrate into URINE. Each renal tubule consists of a BOWMAN CAPSULE; PROXIMAL KIDNEY TUBULE; LOOP OF HENLE; DISTAL KIDNEY TUBULE; and KIDNEY COLLECTING DUCT leading to the central cavity of the kidney (KIDNEY PELVIS) that connects to the URETER.	Kidney Tubule,Tubule, Kidney,Tubules, Kidney
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D011766	Pyruvate Carboxylase	A biotin-dependent enzyme belonging to the ligase family that catalyzes the addition of CARBON DIOXIDE to pyruvate. It is occurs in both plants and animals. Deficiency of this enzyme causes severe psychomotor retardation and ACIDOSIS, LACTIC in infants. EC 6.4.1.1.	Carboxylase, Pyruvate
D002245	Carbon Dioxide	A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.	Carbonic Anhydride,Anhydride, Carbonic,Dioxide, Carbon
D005943	Gluconeogenesis	Biosynthesis of GLUCOSE from nonhexose or non-carbohydrate precursors, such as LACTATE; PYRUVATE; ALANINE; and GLYCEROL.
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000042	Absorption	The physical or physiological processes by which substances, tissue, cells, etc. take up or take in other substances or energy.
D000141	Acidosis, Renal Tubular	A group of genetic disorders of the KIDNEY TUBULES characterized by the accumulation of metabolically produced acids with elevated plasma chloride, hyperchloremic metabolic ACIDOSIS. Defective renal acidification of URINE (proximal tubules) or low renal acid excretion (distal tubules) can lead to complications such as HYPOKALEMIA, hypercalcinuria with NEPHROLITHIASIS and NEPHROCALCINOSIS, and RICKETS.	Renal Tubular Acidosis,Renal Tubular Acidosis, Type I,Renal Tubular Acidosis, Type II,Type I Renal Tubular Acidosis,Type II Renal Tubular Acidosis,Acidosis, Renal Tubular, Type I,Acidosis, Renal Tubular, Type II,Autosomal Dominant Distal Renal Tubular Acidosis,Classic Distal Renal Tubular Acidosis,Distal Renal Tubular Acidosis,Proximal Renal Tubular Acidosis,RTA, Classic Type,RTA, Distal Type, Autosomal Dominant,RTA, Gradient Type,RTA, Proximal Type,Renal Tubular Acidosis 1,Renal Tubular Acidosis I,Renal Tubular Acidosis II,Renal Tubular Acidosis, Distal, Autosomal Dominant,Renal Tubular Acidosis, Proximal,Renal Tubular Acidosis, Proximal, with Ocular Abnormalities,Classic Type RTA,Classic Type RTAs,Gradient Type RTA,Gradient Type RTAs,Proximal Type RTA,Proximal Type RTAs,RTAs, Classic Type,RTAs, Gradient Type,RTAs, Proximal Type
D001639	Bicarbonates	Inorganic salts that contain the -HCO3 radical. They are an important factor in determining the pH of the blood and the concentration of bicarbonate ions is regulated by the kidney. Levels in the blood are an index of the alkali reserve or buffering capacity.	Bicarbonate,Bicarbonate Ions,Hydrogen Carbonates,Bicarbonate Ion,Carbonic Acid Ions,Hydrogen Carbonate,Carbonate, Hydrogen,Carbonates, Hydrogen,Ion, Bicarbonate,Ions, Bicarbonate,Ions, Carbonic Acid