The use of therapies to modulate plasma PAI-1 levels in human subjects have met with variable success. Low salt diet was shown to increase plasma PAI-1 levels in normotensive subjects in a manner that correlated with plasma aldosterone levels. Twice daily treatment with quinapril (40mg) lowered plasma PAI-1 levels during the expected peak time. In a second study of twice daily quinapril compared to twice daily losartan in normotensive subjects both only had a modest effect on plasma PAI-1 levels. A third study helped to explain this finding. In a crossover study, hypertensive subjects received daily spironolactone or hydrochlorothiazide (HCTZ) in a randomized fashion. Plasma PAI-1 levels were increased after HCTZ treatment, but not significantly changed from baseline with spironolactone treatment. Spironolactone treatment, however, resulted in significantly higher aldosterone levels. The correlation between plasma aldosterone and PAI-1 that was observed at baseline and with HCTZ treatment was not observed in the spironolactone arm, suggesting that the endogenous relationship between aldosterone and PAI-1 can be disrupted by mineralocorticoid receptor antagonism.