Altered expression and activity of G-proteins, mitogen activated protein kinases, and tyrosine kinases in aging kidney cortex

• Published in: Journal of investigative medicine Vol. 47; no. 9; pp. 462 - 467
• Main Authors: Parekh, V V, Maier, K G, Roman, R J, Joshua, I G, Falcone, J C, Passmore, J C
• Format: Journal Article
• Language: English
• Published: England 01-11-1999
• Subjects: Aging - metabolism; Animals; Binding Sites; Biomarkers; GTP-Binding Proteins - biosynthesis; Guanosine Diphosphate - metabolism; Guanosine Triphosphate - metabolism; Kidney Cortex - enzymology; Male; Mitogen-Activated Protein Kinases - biosynthesis; Phosphorylation; Protein-Tyrosine Kinases - biosynthesis; Rats; Rats, Wistar; Signal Transduction - physiology
• ISSN: 1081-5589

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.
The present study compared the expression and activity of G alpha i(1-3) and G alpha s 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.
The GTP/(GTP + GDP) binding ratio of G alpha s was significantly decreased in the kidney cortex of aging rats compared to young rats, while the GTP/(GTP + GDP) binding ratio of G alpha i(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.
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 alpha i(1-3) and G alpha s may contribute to the age-related decline in renal tubular and vascular function seen in aging animals.