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

High potassium diets greatly reduce intimal and medial thickening in stroke-prone spontaneously hypertensive rats (SHRSP). In vascular smooth muscle cells, transforming growth factor-beta (TGF-beta) inhibits proliferation. To test whether high potassium diets decrease aortic thickening through TGF-beta, we measured TGF-beta-like activity in medium bathing aortas from rats fed either normal potassium or high potassium diets. Five-week-old SHRSP were fed 6% high NaCl 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-beta-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%, p less than 0.03). Antibodies to TGF-beta 1 and TGF-beta 2 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-beta. 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 less than 0.001, n = 13). The increased growth inhibition of high potassium aortas was not due to an increased release of heparin.(ABSTRACT TRUNCATED AT 250 WORDS)