EXPRESSION OF THE DOPAMINE D-3 RECEPTOR PROTEIN IN THE RAT-KIDNEY

The dopamine D-3 receptor subtype was identified in rat kidney using b oth light microscopic immunohistochemistry and electron microscopic im munocytochemistry. Antipeptide polyclonal antisera were directed to bo th extracellular and intracellular regions of the native D-3 receptor. Selectivity of the antipeptide antisera was validated by their abilit y to recognize native receptor protein expressed in permanently transf ected mouse LTK- cells or Spodoptera fragiperda (Sf9) cell membranes. Light microscopic immunohistochemical staining for the D-3 receptor wa s observed only in the cortex. Specific staining was present in proxim al and distal tubules, cortical collecting ducts, glomeruli, and renal vasculature. Immunostaining was observed predominantly in the apical portion of both the proximal and distal tubules. Renal arterial staini ng was prominent in the medial and adventitial layers. Electron micros copic immunocytochemistry revealed immunogold particles in arteriolar smooth muscle cells of the renal vasculature. In proximal and distal t ubules and cortical collecting duct, immunogold staining was localized to apical portions of tubule cells. D-3 receptor immunogold staining in the glomeruli was clearly present in podocytes. Western blot analys is demonstrated a single D-3 receptor band in infected Sf9 cell membra nes, in transfected LTK- cells, and in kidney and brain but not in non infected Sf9 cell membranes or in D-2 or D-3 receptor transfected or n ontransfected LTK- cells. The use of receptor subtype-selective antibo dies allows for the tissue localization of specific dopamine receptors that are not distinguished by current pharmacological or ligand-bindi ng technology. The rat kidney expresses the D-3 receptor at sites prev iously deemed to have D-2-like receptors.