Altered Expression and Activity of G-proteins,Mitogen Activated Protein Kinases,and Tyrosine Kinases in Aging Kidney Cortex

Abstract

Background

Renal function declines with age and this may be related to changes in the expression or activity of various signal transduction proteins in the kidney.

Methods

The present study compared the expression and activity of G_αi(1-3) and G_αs, phosphorylation of mitogen activated protein kinases (MAP-K) (44 and 42 kd) and the activity of tyrosine kinase in renal cortical homogenates of young (4-month-old) and aging (14-month-old) rats.

Results

The GTP/(GTP+GDP) binding ratio of G_αs was significantly decreased in the kidney cortex of aging rats compared to young rats, while the GTP/(GTP+GDP) binding ratio of G_αi(1-3) increased significantly in kidney cortex of aging rats. Tyrosine kinase activity and phosphorylation of MAP-K (44 and 42 kd) were also reduced in the kidney cortex of aging rats compared to young rats.

Conclusions

These results suggest that diminished phosphorylation of MAP-K and tyrosine kinase activity as well as changes in the binding of GTP/(GTP+GDP) to G_αi(1-3) and G_αs may contribute to the age-related decline in renal tubular and vascular function seen in aging animals.