INSULIN-LIKE EFFECTS ON LIVER GOLGI MEMBRANE PREPARATIONS OF BIS(OXALATO)OXOVANADATE(IV) COMPLEX ION, A NEW VANADATE COMPOUND

Recent studies have shown the insulin-like effect of vanadyl sulphate or sodium ortho (or meta-)vanadate administered orally to rats. Toxici ty of these drugs and reluctance by the animals to drink the solutions and take food, concerning the amelioration of some diabetes syndrome discussed in 1994 by Domingo et al. (1), McNeill et al. (2) and Wiliam s and Malabu (3), prompted us to investigate a new vanadate complex: d isodium bis(oxalato)oxovanadate(IV), Na-2[VO(OX)(2)]. H2O. The main ob ject of the experiment was to study whether this complex administered as 3 mmol/l solution in 0.5% NaCl during 7 days could act on the subce llular level and influence the activity of liver Golgi membrane galact osyltransferase activity. Free blood sugar level was lowered (but was still higher than in the control group) in diabetic rats after seven d ays of vanadate action and was accompanied by lowered, however not sta tistically significant, serum triglyceride levels. The yields of isola ted Golgi-rich membrane fractions were about half of the level in diab etic groups (untreated and treated with vandium) compared with the con trol groups. Purity of these membrane fractions, expressed as nmol Gal transferred per mg of proteins and per h, was the same in four groups investigated and showed the possibility to compare them. Activity of galactosyltransferase calculated in nmol Gal transferred per 1 g of li ver and per 1 h or per whole liver in the same time (as a possibility of glycosylation of the secretory and membrane glycoproteins) was lowe r in both diabetic groups. However, after vanadium treatment (D + V gr oup), the activity was higher than in untreated diabetic rats (D group ) in three of five investigated animals. Vanadyl-oxalate complex did n ot normalize in a statistically significant manner the enzyme activity which was significantly lower in diabetes than in control. This is si milar to insulin influence on the galactosyltransferase activity repor ted previously by Kaczmarski et al. in 1981 (4) and Kordowiak et al. i n 1981 (5).