Patients with pathologic conditions involving constriction or proliferation of smooth muscle or disease associated with cysteine containing proteins, or who are at risk for such, are administered a therapeutically effective amount of a nitric oxide (NO) donor which is insufficient to acutely lower mean arterial blood pressure or pulmonary artery pressure by more than 10%. In one subgenus, NO donor is administered to modify red blood cell membrane receptors to prevent red blood cells from causing vasoconstriction. A related method which allows increased dosage of NO donor without acutely lowering mean arterial blood pressure comprises administering the NO donor into an artery of the patient. In another method, patients having a cardiovascular syndrome, or who are at risk for such, are administered a therapeutically effective amount of thiol which does not acutely affect blood pressure to a significant degree.