Effects of hyperbaric exposure on the levels of plasma endothelin-1, serum nitric oxide and nitric oxide synthase activity in rats

Abstract

Objective To explore effects of hyperbaric exposure on the levels of serum nitric oxide (NO) and plasma endothelin-1(ET-1), and nitric oxide synthase (NOS) activity in rats. Methods Forty SD rats were randomly divided into 5 groups, i.e. group A (the control group), group B (safe decompression to normal pressure following 0.7 MPa air exposure), group C (fast decompression to normal pressure following air exposure at the same pressure), group D (safe decompression to normal pressure following 0.147 MPa pure oxygen exposure), and group E (safe decompression to normal pressure after 0.250 MPa pure oxygen exposure). Exposure durations for all the groups were 60 minutes. Serum concentrations of NO were determined with the nitrate reductase method, activity of NOS in rats was determined with the coiorimetric method, and plasma concentrations of ET-1 were analyzed by using the radioimmunoassay (RIA) technique. Results When compared with that of the control group, plasma concentrations of ET-1 in the safe decompression groups and the HBO groups increased significantly(P<0.05), which might be due to exposure to high partial pressure of oxygen (PO2 = 0.147 MPa/0.250 MPa). Serum concentrations of NO and NOS activity of the fast decompression groups increased significantly (P<0.05). When compared with those of the 3 groups with increased ET-1 in plasma, serum NO and NOS increased more significantly (P<0.01). Conclusions Hyperbaric exposure might bring about an antagonistic effect on NO and ET-1, when animals were exposed to the hyperbaric environment. Hyperbaric and HBO exposure might induce more release of ET-1, and fast decompression load probably induced higher increase in NO. This phenomenon might be one of the stress responses of the vascular endothelial system to the endovascular bubbles. Key words: Hyperbaric exposure; Nitric oxide (NO); Nitric oxide synthase (NOS); Endothelin-1(ET-1)