Carbamylated hemoglobin and carbamylated plasma protein in hemodialyzed patients.

The carbamylation reaction in vivo involves the nonenzymatic, covalent attachment of isocyanic acid, the spontaneous dissociation product of urea, to proteins. Carbamylated proteins have been proposed as markers of uremia and indicators of uremic control. However, the utility of measuring carbamylated proteins has not been investigated adequately.

Carbamylation of erythrocyte membrane proteins: an in vitro and in vivo study.

Objectives: To establish the degree of erythrocyte membrane protein carbamylation in uremic and nonuremic patients, and to characterize the in vitro binding of cyanate to the individual proteins of the cytoskeletal matrix.

Design And Methods: For in vivo studies, erythrocyte ghosts were digested with proteinase K and the released peptides colorimetrically assayed for carbamylation, using the diacetyl monoxime reagent, and quantitated using homocitrulline. For in vitro studies, erythrocyte ghosts were incubated with [14C] cyanate, and the membrane proteins separated by SDS-PAGE.

Low-density lipoprotein binding assay using the calf adrenocortical low-density lipoprotein receptor.

The low-density lipoprotein (LDL) receptor was purified to a semipure solubilized form from calf adrenocortical tissue. This receptor was found to be a suitable substitute for the human LDL receptor for studying human LDL binding. The apparent dissociation constant of the receptor from calf adrenocortical cells, using human LDL as the ligand, was found to be 8.

Glycated calmodulin from platelets as an index of glycemic control.

In an effort to test whether a significant fraction of calmodulin would become glycated within the life span of the platelet (10-14 days), we monitored the kinetics of calmodulin glycation in vitro. Under the conditions we used, the fraction of glycated calmodulin reached a maximum (approximately 21%) within 10 days. We then extended the studies to human subjects.

Glutathione metabolic enzyme activities in diabetic platelets as a function of glycemic control.

Type 1 diabetic subjects categorized on the basis of the glycated haemoglobin content of their blood (low less than 7%; medium, greater than 7% and less than 11%; high, greater than 11%) were analyzed for total intraplatelet GSH as well as for the steady-state kinetic parameters (apparent KM and apparent Vmax) of some glutathione metabolic enzymes including glutathione reductase, glutathione peroxidase, gamma-glutamyltrans-peptidase and glutathione-S-transferase. This study indicates that intraplatelet GSH content of subjects with low glycated-haemoglobin is approximately 2-fold higher than those with medium glycated-haemoglobin. There was no further decrease in intraplatelet-GSH in subjects with high glycated-haemoglobin.