PLASMA-DERIVED SERUM FROM HYPERTENSIVE RATS DIFFERENTIALLY INCREASES GROWTH OF CULTURED ARTERIOLAR SMOOTH-MUSCLE

A role for humoral factors in the arterial hypertrophy accompanying hy pertension has been suggested, but direct evidence is lacking. We meas ured [H-3]thymidine incorporation of growth-arrested smooth muscle cel ls, cultured from renal preglomerular arterioles of normal rats and ex posed for 12 h to 10% platelet-poor plasma-derived serum (PDS) from ma le rats with early, benign, one-kidney, one-clip hypertension and pair ed one-kidney normotensive control rats. In the presence of low backgr ound concentrations (1-2%) of fetal calf serum, PDS from hypertensive rats increased [H-3]thymidine incorporation up to 117% more than PDS f rom normotensive rats (P < 0.0001). Results were similar for the <10,0 00 mol wt fraction of PDS and for PDS from rats drinking saline vs. wa ter or eating a 7% (high) vs. a 0.45% NaCl diet. PDS from hypertensive rats also differentially increased smooth muscle cell proliferation a nd c-fos mRNA expression. Platelet-derived growth factor levels in PDS were undetectable (< 0.17 ng/ml). This study provides evidence for al tered concentrations of sodium chloride-unresponsive plasma factor or factors in hypertension that result in enhanced growth of arteriolar s mooth muscle cells.