Effect of chronic salt loading on collagen content in thoracic aorta and the expression of TGFβ1 in spontaneously hypertensive rats

Objective: To make a dynamic observation on the effect of chronic salt loading on collagen content in thoracic aorta and the expression of TGFβ1 in spontaneously hypertensive rats (SHR) and investigate the possible mechanism. Methods: SHRs (80 in number, male, 4-5 weeks old) were assigned randomly to receive 4% (g/kg) high salt (HS groups, n = 45) and 0.4% low salt (LS groups, n = 35) for 16 weeks. Blood pressure, urine volume and urinary sodium excretion were measured every four weeks. These rats were sacrificed randomly at the start of this study, 4th, 8th, 12th and 16th week, 6 rats in each group each time. The aorta was collected and dyed with Masson to observe the pathological change of thoracic aorta under microscope; microholography system was used to calculate collagen volumetric fraction (CVF) of the aorta. Expression of TGFβ1 in SHR thoracic aorta was measured with immunohistochemical method. Results: Circled digit one CVF in thoracic aorta was increased significantly in HS group compared with that in LS group at 4th, 8th, 12th and 16th week (P<0.05). Circled digit two Compared with that in LS group, the expression of TGFβ1 in HS group was increased at 4th, 8th and 12th week (P<0.05). Conclusion: Chronic salt loading can increase collagen content in thoracic aorta of SHR. Local TGFβ1 increase induced by salt loading in SHR is probably involved in the development of collagen increase.