REGULATION OF NA-ATPASE GENE-EXPRESSION BY INSULIN IN VASCULAR SMOOTH-MUSCLE CELLS(,K+)

Na+,K+-ATPase gene expression and activity and its modulation by insul in were investigated in vascular smooth muscle cells (VSMC). Messenger RNAs encoding for alpha1- and alpha2-isoforms of Na+,K+-ATPase were i dentified in a pure population of cultured VSMC (a7r5 cells). The pred ominant isoform in VSMC was alpha2, but only alpha2 was regulated by i nsulin. Insulin treatment of VSMC for 1 and 6 h caused significant inc reases in mRNA encoding the alpha2-subunit of Na+,K+-ATPase (n = 7, P < .01). Under similar conditions, insulin had no effect on alpha1-Na+, K+-ATPase mRNA levels. VSMC treated with insulin exhibited a significa nt stimulation of ouabain inhibitable ATPase activity (1 h insulin, n = 3, v control, n = 3, P < .025; 6 h insulin, n = 3, v control, n = 3, P < .05). Changes in insulin regulation of Na+,K+-ATPase gene express ion in vascular smooth muscle may be an important factor in the develo pment of hypertension in diabetes.