Biomaterial Database

Sodium activation kinetics of red blood cell Na+/Li+ countertransport in diabetes: methodology and controversy. 1992

M Canessa, and G Zerbini, and L M Laffel

Endocrine-Hypertension Division, Brigham and Women's Hospital, Boston, MA 02115.

Although many studies report an elevated Vmax of red blood cell Na/Li countertransport (CTT) activity in patients with insulin-dependent diabetes mellitus (IDDM) complicated by renal disease, divergent reports exist. This article reviews the technical issues and selection criteria that fuel this controversy. In addition, new studies from this laboratory indicate that insulin in vitro and in the nonfasted state modulate CTT activity and may contribute to the discrepant findings. Incubation of red blood cells from fasted controls with physiologic concentrations of insulin induced a twofold increase in the Km for external Na+. Similarly, Na+ activation kinetics of Li+ efflux showed saturation between 50 and 150 mM Na+ in fasted controls whereas saturation, postprandially, occurred between 100 and 150 mM Na+ as a result of an increase in Km. To clarify the role of prandial status on the measurement of Na+/Li+ CTT activity in diabetes, Na+ activation kinetics were investigated in 34 nonfasting patients with IDDM. Li+ efflux was fully saturated between 80 and 150 mM Na+ in the normoalbuminuric subjects (N = 22), whereas saturation occurred between 150 and 280 mM Na+ in the patients with diabetic nephropathy (N = 14). Patients with nephropathy have higher values of Km for Na+ than do the patients free of renal complications (86 +/- 9.5 versus 41.3 +/- 3.4 mM Na+, respectively; P < 0.000012). The higher Km prevented complete saturation of Li+ efflux at 150 mM extracellular Na+ concentration and contributed to the underestimation of Vmax at 150 mM Na+ selectively in persons with renal complications.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D007328	Insulin	A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1).	Iletin,Insulin A Chain,Insulin B Chain,Insulin, Regular,Novolin,Sodium Insulin,Soluble Insulin,Chain, Insulin B,Insulin, Sodium,Insulin, Soluble,Regular Insulin
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008094	Lithium	An element in the alkali metals family. It has the atomic symbol Li, atomic number 3, and atomic weight [6.938; 6.997]. Salts of lithium are used in treating BIPOLAR DISORDER.	Lithium-7,Lithium 7
D008722	Methods	A series of steps taken in order to conduct research.	Techniques,Methodological Studies,Methodological Study,Procedures,Studies, Methodological,Study, Methodological,Method,Procedure,Technique
D002352	Carrier Proteins	Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes.	Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D003922	Diabetes Mellitus, Type 1	A subtype of DIABETES MELLITUS that is characterized by INSULIN deficiency. It is manifested by the sudden onset of severe HYPERGLYCEMIA, rapid progression to DIABETIC KETOACIDOSIS, and DEATH unless treated with insulin. The disease may occur at any age, but is most common in childhood or adolescence.	Diabetes Mellitus, Brittle,Diabetes Mellitus, Insulin-Dependent,Diabetes Mellitus, Juvenile-Onset,Diabetes Mellitus, Ketosis-Prone,Diabetes Mellitus, Sudden-Onset,Diabetes, Autoimmune,IDDM,Autoimmune Diabetes,Diabetes Mellitus, Insulin-Dependent, 1,Diabetes Mellitus, Type I,Insulin-Dependent Diabetes Mellitus 1,Juvenile-Onset Diabetes,Type 1 Diabetes,Type 1 Diabetes Mellitus,Brittle Diabetes Mellitus,Diabetes Mellitus, Insulin Dependent,Diabetes Mellitus, Juvenile Onset,Diabetes Mellitus, Ketosis Prone,Diabetes Mellitus, Sudden Onset,Diabetes, Juvenile-Onset,Diabetes, Type 1,Insulin Dependent Diabetes Mellitus 1,Insulin-Dependent Diabetes Mellitus,Juvenile Onset Diabetes,Juvenile-Onset Diabetes Mellitus,Ketosis-Prone Diabetes Mellitus,Sudden-Onset Diabetes Mellitus
D003928	Diabetic Nephropathies	KIDNEY injuries associated with diabetes mellitus and affecting KIDNEY GLOMERULUS; ARTERIOLES; KIDNEY TUBULES; and the interstitium. Clinical signs include persistent PROTEINURIA, from microalbuminuria progressing to ALBUMINURIA of greater than 300 mg/24 h, leading to reduced GLOMERULAR FILTRATION RATE and END-STAGE RENAL DISEASE.	Diabetic Glomerulosclerosis,Glomerulosclerosis, Diabetic,Diabetic Kidney Disease,Diabetic Nephropathy,Intracapillary Glomerulosclerosis,Kimmelstiel-Wilson Disease,Kimmelstiel-Wilson Syndrome,Nodular Glomerulosclerosis,Diabetic Kidney Diseases,Glomerulosclerosis, Nodular,Kidney Disease, Diabetic,Kidney Diseases, Diabetic,Kimmelstiel Wilson Disease,Kimmelstiel Wilson Syndrome,Nephropathies, Diabetic,Nephropathy, Diabetic,Syndrome, Kimmelstiel-Wilson
D004912	Erythrocytes	Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.	Blood Cells, Red,Blood Corpuscles, Red,Red Blood Cells,Red Blood Corpuscles,Blood Cell, Red,Blood Corpuscle, Red,Erythrocyte,Red Blood Cell,Red Blood Corpuscle
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23