Correlation of platelet size and platelet survival

Correlation of platelet size and platelet survival

272 ABSTRACTS FROM SYMPOSIUM HONORING DR. BESSMAN enzymes ofglucose utilization as well as those engaged in UDP sugar formation or in the hydi-ox...

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272

ABSTRACTS

FROM SYMPOSIUM

HONORING

DR. BESSMAN

enzymes ofglucose utilization as well as those engaged in UDP sugar formation or in the hydi-oxylation and glycosylation processes (required for glycoprotein synthesis) show increased activity in the diabetic kidney. while the catabolic, lysosomal enzymes tcathepsin D and several glycosidasezt are depressed. We observed a reduction of 24% in the activity of cathepsin D and 23% in that of’ galactosidase in the kidney of streptozotocin-diabetic mice. as opposed to an increase of 1!cI’,:, and of 32%, respectively, found in liver. It is not known which factor(s) may be responsible for \uch an anabolic response of some tissues to diabetes. but persistent hyperglycemia and/or some hormonal abnormalities may be involved. The above data refer to changes in tissue enzyme content caused by induction-repression mechanisms; but rapid (activation-inhibition) effects may also occur. Wr observed that preincubation of slices of mouse kidney cortex for IO mitt with 20.8 mmole/liter glucose resulted in an 80% activation of phosphofructokinase. as assayed in the tissue homogenate at physiological (50 pmole/liter) concentration of the substrate fructose-6-P. suggesting that hyperglycemia may he responsible for some of the metabolic changes occurring in the diabetic kidney. Correlution

of Platelet

Size and Platelet

J. 1). BESSMA>~R. M. DE\\r\. 1.. (‘. How ‘\KLI. and Biochemistry. University of Texas Medical

Sur~~iLul.

F. H. GARDNER, Departments of Medicine Branch. Galveston. Texas. AND

Platelet size (mean platelet volume. MPV) often has been considered a reflection of platelet
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R. C. BROWN, Department of Pharmacology and Nutrition, University of Southern C’alifornia School of Medicine. 2025 Zonal Avenue. Los Angeles. California 90033. AND

Isolated parenchymal cells were prepared from rat liver using collagenasc perfusion. and pm tlicd by a self-generating percoll gradient. To evaluate drug metabolism and conjugation, I’-nitroanisole (pNA) was used. pNA is O-demethylated to p-nitrophenol (pNPl by the cytochrome P-450 dependent mixed function oxidase (MFOl and in turn is conjugated by sulfotransferase (ST) to pNP-sulfate (pNPS) and by glucuronyl transferase (GT) to pNP-glucuronide lpNPG1. In control (magnesium sufficient) cells the formation of pNP increased relative to the pNA concentration. At the loue~ concentrations of pNA. sulfalion of pNP was the primary conjugate, while at higher pNA concentration\ glucuronidation increased. The amount of free (nonconjugated) pNP also increased in proportion ti) the amount of pNA metabolized. Hepatocytes prepared from Mg-depleted animal\ metabolized Jr\\ pNA to pNP, suggesting loss of MFO activity. Although lower in concentration. the metaboiite pattern for both pNP and PNP-sulfate (pNPSl remained similar IO that observed in the cnntrol cells However, glucuronidation was greatly diminished. The loss of both MFO and GT activities suggest