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At least 613 records · Page 34Linked to original sources
PubMed1985

Reduced glomerular sodium/potassium adenosine triphosphatase activity in acute streptozocin diabetes and its prevention by oral sorbinil.

To explore metabolic changes associated with the sorbitol accumulation and myo-inositol depletion observed in glomeruli of rats with experimental diabetes, we examined total and ouabain-inhibited adenosine triphosphatase (ATPase) activity in glomeruli isolated from control and streptozocin (STZ)-diabetic rats. Glomerular Na/K-ATPase activity (ouabain-inhibited) was significantly reduced in diabetic animals, while total (composite) ATPase activity remained unchanged. Treatment with insulin partially restored the Na/K-ATPase activity. Administration of the aldose reductase inhibitor, sorbinil, which normalizes glomerular contents of both sorbitol and myo-inositol in diabetes, completely prevented the diminution of Na/K-ATPase activity. These results establish that glomerular Na/K-ATPase activity is reduced in acute experimental diabetes. The ability of sorbinil to prevent this decrease suggests that it is related to polyol accumulation and/or myoinositol depletion, although an effect of the drug unrelated to its aldose reductase inhibiting property has not been excluded. Since increased polyol pathway flux, decreased myo-inositol, and reduced Na/K-ATPase activity have also been described in peripheral nerve, another tissue in which typical diabetic complications characteristically occur, the consequences of these metabolic changes may be implicated in the pathogenesis of diabetic nephropathy.

Adenosine Triphosphatases↗
PubMed2000

The effects ex vivo and in vitro of insulin and C-peptide on Na/K adenosine triphosphatase activity in red blood cell membranes of type 1 diabetic patients.

The decrease in Na/K adenosine triphosphatase (ATPase) activity observed in several tissues of type 1 diabetic patients is thought to play a role in the development of long-term complications. Infusion of insulin may restore this enzyme activity in red blood cells (RBCs), and recent arguments have been developed for a similar role of C-peptide. The aims of this study were to determine whether insulin acts directly on the RBC enzyme and to evaluate the effect of C-peptide on Na/K ATPase activity. Thirty-nine C-peptide-negative type 1 diabetic patients were studied (blood glucose, 11.2 +/- 1.49 mmol/L; hemoglobin A1c [HbA1c], 8.9% +/- 0.1%, mean +/- SEM). Blood samples were obtained in the morning, before breakfast and insulin injection. Intact and living RBCs were resuspended in their own plasma and incubated with or without insulin (50 microU/mL) or C-peptide (6 nmol/L). Ex vivo by microcalorimetry, the heat produced after 1 hour by the enzyme-induced hydrolysis of adenosine triphosphate (ATP), was measured in a thermostated microcalorimeter at 37 degrees C. The results showed that Na/K ATPase activity was significantly increased by insulin (12.4 +/- 0.5 v 15.4 +/- 0.9 mW/L RBCs, P < .05, n = 23) but not by C-peptide (11.9 +/- 0.7 v 12.9 +/- 0.9 mW/L RBCs, NS, P = .26, n = 12). In another experiment, RBC suspensions were incubated at 37 degrees C in a water bath with or without insulin (50 microU/mL) or C-peptide (6 nmol/L) for 10 minutes. RBC membranes were isolated and Na/K ATPase activity was assessed by measuring inorganic phosphate release at saturating concentrations of all substrates. The results showed that insulin and C-peptide significantly increased RBC Na/K ATPase activity (342 +/- 25, P < .005 and 363 +/- 30, P < .005, respectively v255 +/- 22 nmol Pi x mg protein(-1) x h(-1), n = 14). We conclude that insulin and C-peptide act directly on RBC Na/K ATPase, thus restoring this activity in type 1 diabetic patients. The stimulatory effect of C-peptide observed in vitro on RBC Na/K ATPase activity confirms that C-peptide plays a physiological role.

Adult↗
PubMed1986

A new histochemical method for magnesium actomyosin adenosine triphosphatase at physiological pH.

A new lead-precipitation technique for demonstrating magnesium-activated actomyosin adenosine triphosphatase (ATPase) at physiological pH and electrolyte levels in fixed skeletal muscle sections is reported. This method is compared with standard acid- and alkali-denatured muscle stained for calcium myosin ATPase as well as calcium-formalin denatured and pyrophosphate-formalin denatured muscle also stained for calcium myosin ATPase. The technique was developed using hamster skeletal muscle; however, it has also been applied to human, rat, and cat muscle. The fiber-type staining intensities of the formalin-denatured magnesium actomyosin ATPase closely resemble those of the formalin-denatured calcium myosin ATPase in rodents, but intensities in Type 1 fibers are reversed relative to calcium myosin ATPase in human muscle. Cat muscle shows intermediate characteristics.

Actomyosin↗