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Correlation of diacylglycerol level and protein kinase C activity in rat retina to retinal circulation
Ist Teil von
American journal of physiology: endocrinology and metabolism, 1993-11, Vol.265 (5), p.E783-E793
Ort / Verlag
United States
Erscheinungsjahr
1993
Quelle
MEDLINE
Beschreibungen/Notizen
T. Shiba, T. Inoguchi, J. R. Sportsman, W. F. Heath, S. Bursell and G. L. King
Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02215.
The increases in diacylglycerol (DAG) level and protein kinase C (PKC)
activity have been characterized biochemically and functionally in the
retina and the brain of diabetic rats as well as in cultured vascular
cells. PKC specific activities were increased in the membraneous fraction
of retina from streptozotocin (STZ)-induced diabetic rats and the
genetically determined diabetic BB rats, respectively, after 1 or 2 wk of
diabetes, compared with control. The ratio of total PKC activities from
membraneous and cytosol fractions was also increased in the retina of
diabetic rats. With diabetes, all the isoenzymes and the total DAG level
were increased in the rat retina, whereas no changes were found in the rat
brain. Insulin treatment normalized plasma glucose levels and partially
prevented the increases in the membraneous PKC activity and all the
isoenzymes in the retina. In the retinal endothelial cells, the total DAG
level and PKC specific activities are increased by 36 and 22%,
respectively, in the membraneous pool when the glucose levels are changed
from 5.5 to 22 mM. Activation of PKC activity and isoform beta II by the
vitreal injection of phorbol dibutyrate mimicked the abnormal retinal blood
circulation observed in diabetic rats (2.22 +/- 0.24 vs. 1.83 +/- 0.40 s).
Thus diabetes and elevated glucose levels will increase DAG level and PKC
activities and its isoenzyme specifically in vascular cells and may affect
retinal hemodynamics.