Discussion
The results of the present study indicatedindicate that consumption of NaCl with a concentration of 1.5% (w/v) in distilled water as drinking water in Wistar rats for 8 weeks; caused a significant increase in the expression of the CHOP gene as well as mild fibrosis in kidney tissue. It is worth taking tointo consideration that this mild fibrosis did not affect renal function. Biochemical indicators of renal function such as urea, creatinine in blood and urine, and total protein in urine are not significantly different in comparison with the normal control group; buthowever, the concentration of Kim-1KIM-1 increased significantly in urine. Additionally, a significant direct correlation coefficient was observed between the relative gene expression of CHOP in kidney tissue and Kim-1KIM-1 in urine.
To justify these results, it should be added that in previous studies, it has been observed that excessive and prolonged consumption of salt, which causes osmotic stress, can lead to ER stress. On the other hand, ER stress will significantly increase the expression of the CHOP gene in kidney tissue (8, 9). In connection with the increase in the expression of the CHOP gene in kidney tissue and the development of fibrosis, it should be added that the CHOP protein is knownrecognized as an important apoptosis stimulator. Extensive apoptosis, in turn, can cause inflammation and fibrosis of kidney tissue (7, 9, 18). During inflammation, the outer part of Kim-1KIM-1 separates from the membrane and appears in urine. It should be noted that, before extensive fibrosis of renal tissue, Kim-1KIM-1 is detectable in urine (14). Researchers believe that Kim-1KIM-1 can be an early diagnostic marker of renal tissue fibrosis, and there may be a direct relationship between the amount of this protein in urine and severity of renal fibrosis (19).