High-energy photons vs protons in their action on vascular function in rats

The goal of this work was to compare the effects of a photon (PTI) and proton/hadron (HTI) irradiation on rat’s cardiovascular system. Cardiovascular functions were studied in rats after PTI and HTI impact in the equivalent total absorbed dose of 6 Gy. Photons were delivered using 60Co gamma-rays (0.8 Gy min-1). The particle irradiation was done by using a 9,6×10-12 J proton beam accelerated in the U-240 isochronous cyclotron. Both PTI and HTI decreased the acetylcholine-induced relaxation in rat’s aorta smooth muscle (SM) and outward potassium currents in aortic SM cells on the 9th day post-irradiation but HTI appeared to produce a more profound effect. HTI had no significant effect on systolic blood pressure (SBP) in rats while PTI produced clearly defined systemic hypertension. HTI, unlike PTI, significantly increased the left ventricle pressure in Langendorff - perfused rat’s heart. Thus, the biological effects of PTI and HTI on rat’s aorta endothelium-dependent relaxation and net potassium currents in the SM cells appear to be similar, although the effects of HTI are more pronounced. However, PTI, unlike HTI, produced significant systemic hypertension.