Expression of MT-3 protein in the human kidney

The objective of the present study was to determine the expression of MT-3 in the human kidney. To accomplish this, an antibody was generated against a unique 8 amino acid sequence present in MT-3 that is not shared by any ot her MT family member. Western analysis demonstrated that the resulting anti body reacted with a protein band of approximately 6 kDa, corresponding to t he known molecular weight of MT-3. Immunohistochemical staining using this antibody demonstrated reactivity with several epithelial components of the nephron. In the glomerulus, moderate intensity was demonstrated in parietal epithelial cells of Bowman's capsule and in visceral epithelial cells of t he glomerular tuft. Proximal convoluted tubule cells exhibited moderate cyt oplasmic MT-3 reactivity. Distal tubules showed strong cytoplasmic staining for MT-3, particularly in the medullary rays. In the medulla, MT-3 stainin g was the most variable, with weak to moderate staining in the medullary co llecting ducts and a general absence of staining in the thin loops of Henle and in the transitional epithelium of the renal pelvis. The finding that M T-3 is constitutively expressed in several glomerular and tubular epithelia l elements of the human kidney warrants consideration of an expanded role f or this protein family in maintaining renal homeostasis. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.