A study of plasma alpha-2-macroglobulin levels in type 2 diabetic subjects with microalbuminuria.

BACKGROUND: Alpha-2 macroglobulin (Alpha-2-M) is a major plasma protease inhibitor that also regulates the activity of a variety of bioactive peptides including interleukins and exerts a range of immunomodulatory effects. OBJECTIVE: We conducted the present study with the objective to study the alpha-2-M levels in type 2 diabetic subjects with microalbuminuria in an attempt to establish alpha-2-M as a predictor of microvascular complications in diabetes. MATERIAL AND METHODS: Plasma Alpha-2-M levels were assayed in 100 (53 males and 47 females) randomly selected type 2 diabetic subjects with microalbuminuria. Diabetes was diagnosed according to the expert committee report of 1998. Patients with any acute metabolic complication like hypoglycemia, ketoacidosis, cerebrovascular accident or any acute infection were not included in the study group. RESULTS: Majority of patients belonged to 40-60 years age group. In our study alpha-2-M levels indicated a clear increase in diabetic subjects with the increasing age of subjects confirmed by multiple logistical analysis. Alpha-2-M levels were not found to be significantly different between males and females (55.6 +/- 11.3 vs. 53.7 +/- 10.5). Duration of diabetes was found to be an important confounding variable showing a direct positive correlation with alpha-2-M levels and also a significant correlation was found between alpha-2-M levels with different levels of microalbuminuria on multiple logistical analysis. No significant relation of alpha-2-M levels with either fasting blood sugar or HbA1 was observed. CONCLUSION: The increase in plasma alpha-2 macroglobulin levels in diabetes may be a correlative measure to encounter the potential proteolytic challenge associated with diabetic microangiopathy, even very early in the course of the disease. Alph-2 macroglobulin may yet be one of the most specific markers of microvascular complications in diabetes than any other serum protein.

Ca(2+)-induced alterations in the activity of membrane (Ca(2+)-Mg2+)-ATPase of human and rat erythrocytes.

Effect of intraerythrocyte Ca2+ elevation on human and rat erythrocyte membrane (Ca(2+)-Mg2+)-ATPase along with that of incubation of the erythrocyte ghosts in their own hemolysates enriched with Ca2+ has been studied. While the membrane (Ca(2+)-Mg2+)-ATPase levels of Ca(2+)-loaded human erythrocytes showed an initial increase and subsequent decline, membranes incubated in their own hemolysate showed a consistent decrease in the enzyme activity. Calmodulin sensitivity was retained by the preparations in contrast to the earlier observations made with washed erythrocyte membranes. Similar changes in (Ca(2+)-Mg2+)-ATPase activity but of greater magnitude were observed in response to Ca2+ in the calpain-rich rat erythrocytes. Considerable crosslinking and proteolysis was observed in case of human and rat erythrocytes exposed to high Ca2+ concentrations. The Ca(2+)-activable transglutaminase, however, did not play any role in the activation of the (Ca(2+)-Mg2+)-ATPase.

Inactivation and reactivation of horseradish peroxidase immobilized by various procedures.

Horseradish peroxidase (HRP) immobilized by coupling the amino acid side chain amino groups or carbohydrate spikes to the matrix has been studied for its resistance to heat, urea-induced inactivation and ability to regain activity after denaturation in order to understand the influence of the nature of immobilization procedure on these processes. The various immobilized preparations were obtained and their properties studied: Sp-HRP was obtained by direct coupling of HRP to cyanogen bromide-activated Sepharose, Sp-NHHRP by coupling periodate oxidized and diamine-treated enzyme to the cyanogen bromide activated Sepharose, SpNH-COHRP by coupling periodate-treated enzyme to amino-Sepharose and SpCon A-HRP by binding of the enzyme on Con A-Sepharose. All the immobilized preparations exhibited higher stability against heat-induced inactivation as compared to the native HRP. Sp-NHHRP was most stable followed by Sp-HRP, SpNH-COHRP and SpCon A-HRP. Sp-NHHRP was also superior in its ability to regain enzyme activity after thermal denaturation, although Sp-HRP regained maximum activity after urea denaturation. Inclusion of Ca2+ was essential for the reactivation of all preparations subsequent to denaturation by urea.

Goat erythrocyte calmodulin is not abnormal.

Calmodulin was purified from goat erythrocyte hemolysate using heat treatment and Sephadex G-100 gel filtration chromatography. The molecular weight and Stokes, radius of the purified calmodulin was determined. The goat erythrocyte calmodulin stimulated (Ca(2+)-Mg2+)-ATPase but not (Mg2+)-ATPase and (Na(+)-K(+)-Mg2+)-ATPase. The (Ca(2+)-Mg2+)-ATPase of the erythrocyte membrane derived from human, rat, rabbit and pig were significantly stimulated.