CB-P16.
TUBULIN IN THE REGULATION OF GLUCOSE
REDUCTASE AND NA+, K+-ATPASE IN RATS WITH
INDUCED DIABETES
Rivelli JF1, Amaiden MF1, Campetelli AN1, Previtalli G1, Fossati
FA2, Arce CA3, Casale CH1.
1Dpto. Biol. Molec. UNRC. 2Hospital Regional de Río Cuarto.
3CIQUIBIC-UNC. E-mail: jrivelli@exa.unrc.edu.ar
Part of cytosolic tubulin is associated to plasma membrane and
inhibit the Na+, K+-ATPase. We demonstrated that the ATPase
inhibition by tubulin in vitro is reverted by glutamate and reversibly
inhibited by glucose. In erythrocytes of diabetics patients (DP), the
Na+, K+-ATPase is inhibited. To determinate if tubulin is involved
in the inhibition of the enzyme in these patients, we studied the
plasma membrane tubulin of DP?s erythrocytes. Recently we
demonstrated that erythrocytes of DP have increased more than two
fold the content of membrane tubulin. Similar results were found
when COS or CAD cells were incubated with glucose or sorbitol.
This study demonstrate that the membrane tubulin increases
significantly in brain of streptozotocin induced diabetic rats or rats
treated with an intraperitoneal injection of sorbitol. This increase is
correlated with a decrease in Na+, K+-ATPase activity. The origin
of the sorbitol in DP is due to the reduction of glucose by glucose
reductase, therefore we decided to study whether the tubulin had
any influence on the activity of this enzyme. Cytosolic extracts
from rat brain were incubated with a tubulin preparation of the same
tissue. The results show that tubulin is able to inhibit glucose
reductase in vitro. These results show that tubulin could be involved
in regulating glucose reductase and Na+, K+-ATPase activities of
DP.
