Win 58237 (0.3-3.0 mg/kg i.v.) decreases mean arterial pressure in conscious spontaneously hypertensive rats with an associated increase in vascular (aortic) cGMP content in vivo. Win 58237 (10 mg/kg i.v.) increases plasma cGMP levels, from basal levels of 6.7 ± 1.0 to 31.4 ± 3.5 fmol/μL[1].