High potassium diets greatly increase growth-inhibiting agents in aortas of hypertensive rats. Hypertension

High potassium diets greatly reduce intimal and medial thickening in stroke-prone spontaneously hypertensive rats (SHRSP). In vascular smooth muscle cells, transforming growth factor-/? (TGF-/3) inhibits proliferation. To test whether high potassium diets decrease aortic thickening through TGF-/3, we measured TGF-0-like activity in medium bathing aortas from rats fed either normal potassium or high potassium diets. Five-week-old SHRSP were fed 6 % high NaCI diets containing either normal (0.5%) potassium (11 rats) or high (2.1%) potassium (14 rats) for 7 weeks. Aortas were freshly excised and perfused for 3 hours with tissue culture medium at ordinary arterial pressures. TGF-0-like activity in the acid-activated perfusing medium was assessed using the growth inhibitory action on mink lung cells. Growth inhibition was assessed by [3H]thymidine incorporation. In the medium perfusing the outside of the aorta, the growth inhibitory rates were 2.5 times higher in high potassium SHRSP than in normal potassium SHRSP (-49 % versus-20%,/j<0.03). Antibodies to TGF-/3, and TGF-ft were added to other aliquots and did not alter the results whatsoever. Thus, the difference in growth inhibition was not due to differences in TGF-/3. The high potassium aortas released 2.5 times more growth-inhibiting agents than the normal potassium aortas. The same pattern of growth inhibition was also seen using vascular smooth muscle cells rather than mink lung cells (r = +0.818,p<0.001, n = 13). The increased growth inhibition o