The main spectral di ff erences between the biochemical compositions of the vascular endothelium of control, hypertensive NO-de fi cient, and NO-de fi cient mice supplemented with nitrate were studied using Raman microimaging. A signi fi cantly di ff erent Raman signature of the endothelium in these three groups in the 1200 – 1400 cm − 1 region was assigned to the α -helix and β -sheet alterations in the protein second- ary structure upon the development of hypertension. The second pronounced biochemical marker of endothelium alterations was the lipid to protein ratio. A lower intensity of the band at 2940 cm − 1 relative to the feature at 1007 cm − 1 in the endothelium in hypertension compared to the control indicated a decrease of the lipid content relative to proteins during the progress of the pathology. The nitrate-based treatment partially reversed the e ff ects of hypertension. The nitrate supplementation restored the lipid to protein ratio in the endothelium to the control level, while the changes in the secondary structure of pro- teins were irreversible upon nitrate administration.