Albumin is an important vascular tonus regulator as a reservoir of nitric oxide.

Plasma albumin reacts with nitric oxide (NO) to form S-nitroso-albumin (albumin-S-NO). The present study was designed to elucidate whether NO-induced response on blood pressure may differ between analbuminemic rats (NAR) and normal rats. When NOC7, a NO donor, was intravenously injected in rats, blood pressure decreased and the initial depressor response was the same in both the NAR and the normal rats. However, the duration of NO-induced hypotension was 0.5 times longer in NAR than in the normal rat. After NOC7 injection, plasma thiol levels decreased and S-nitrosothiols levels increased in the normal rats, whereas these levels slightly changed in NAR. These results suggested that NO reacts with albumin-SH, resulting in albumin-S-NO formation, which produces a continuous hypotensive response in blood pressure as a slow releaser of NO.