Differential regulation of B/K protein expression in proximal and distal tubules of rat kidneys with ischemia-reperfusion injury

Ki Hwan Han, U. Young Lee, Yoon Seong Jang, Mi Cho Yoon, Min Jang Young, In A. Hwang, Yeon Ghee Jung, Sun Woo Lim, Wan Young Kim, Woo Yang Chul, Jin Kim, Oh Joo Kwon

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Brain/kidney (B/K) protein is a novel double C2-like-domain protein that is highly expressed in rat brain and kidney, but its cellular localization and functional role in the kidney are still undetermined. We examined the cellular localization of B/K protein in the rat kidney under normal and ischemic conditions. Ischemia-reperfusion (I/R) injury was induced by clamping both renal arteries for 45 min, and animals were killed at 1 and 6 h and 1, 2, 3, 5, 7, 14, and 28 days after the reperfusion. Kidney tissues were processed for immunohistochemistry and immunoblot analyses using rabbit anti-B/K polyclonal antibodies. In control kidneys, B/K protein was expressed primarily in distal tubules including the thick ascending limb, distal convoluted and connecting tubules, and collecting duct. Notably, B/K protein was also expressed in the straight portion (S3 segment), but not in the S1 or S2, of proximal tubules, and podocytes of the glomerulus. In rat kidneys with I/R injury, expression of B/K protein was differentially regulated according to the anatomic location. In distal tubules, overall expression of B/K protein was markedly decreased. On the other hand, I/R injury significantly increased B/K protein expression in the S3 segment of the outer medulla as well as in the rat proximal tubular epithelial cell line NRK-52E in vitro. Furthermore, B/K protein was strongly expressed in many exfoliated cells in the lumen and urine. These findings suggest that B/K protein is closely associated with cell death in proximal tubules, which are vulnerable to I/R injury in the kidney.

Original languageEnglish
Pages (from-to)F100-F106
JournalAmerican Journal of Physiology - Renal Physiology
Issue number1
StatePublished - Jan 2007


  • Brain/kidney protein
  • Cell death


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