Kisspeptins are biologically active cleavage peptides of the KiSS-1 gene products with important roles in the suppression of tumor metastasis and in the reproduction. The aim of the present study is to clarify changes of the expression of kisspeptins and kisspeptin receptor in the kidney with and without chronic renal impairment. 5/6 nephrectomized rats were used as the rat model of chronic renal failure. Competitive quantitative RT-PCR showed that kisspeptin mRNA levels were decreased in the kidney of 5/6 nephrectomized rats at 56 days compared with sham-operated rats. In contrast, immunoreactive kisspeptin concentrations were increased in the kidney of 5/6 nephrectomized rats at 56 days. On the other hand, kisspeptin receptor mRNA levels were increased in the kidney of 5/6 nephrectomized rats at 14 and 56 days compared with sham-operated rats. Immunocytochemistry showed that kisspeptins and kisspeptin receptor were expressed in renal tubular cells, collecting duct cells, vascular smooth muscle cells in both rats. The intensity of kisspeptin receptor immunostaining was lower in 5/6 nephrectomized rats than in sham-operated rats. Western blot analysis confirmed that kisspeptin receptor protein levels were significantly decreased in the remnant kidney of 5/6 nephrectomized rats (about 23% of sham-operated rats), which is a good contrast to the kisspeptin receptor mRNA expression. The present study has shown that expression of kisspeptins and kisspeptin receptor are altered in the kidney tissues of chronic renal impairment, raising the possibility of their pathophysiological roles in chronic renal failure.
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