Differential regulation of B/K protein expression in proximal and distal tubules of rat kidneys with ischemia-reperfusion injury.
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.
Han
Ki-Hwan
KH
Department of Anatomy, College of Medicine, Ewha Womans University, Korea.
Lee
U-Young
UY
Jang
Yoon-Seong
YS
Cho
Yoon Mi
YM
Jang
Young Min
YM
Hwang
In-A
IA
Ghee
Jung Yeon
JY
Lim
Sun-Woo
SW
Kim
Wan-Young
WY
Yang
Chul Woo
CW
Kim
Jin
J
Kwon
Oh-Joo
OJ
D000818:Animals; D015153:Blotting, Western; D016923:Cell Death / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism*; D050857:Synaptotagmins; D014556:Urine / Q000166:cytology
D009419:Nerve Tissue Proteins; C409229:Syt17 protein, rat; D050857:Synaptotagmins