Expression of parathyroid hormone receptors in MDCK and LLC-PK1 cells

Parathyroid hormone (PTH) inhibits renal proximal tubular phosphate (P_i) and bicarbonate reabsorption by regulating the activity of apical Na/P_i cotransport and Na/H exchange. Two renal epithelial cell lines [proximal tubular, LLC-PK₁; distal tubular, Madin-Darby canine kidney, (MDCK) cells] were stably transfected with complementary deoxyribonucleic acids (cDNAs) encoding a cloned PTH receptor in order to examine the polarity of transfected receptor function and whether or not intrinsic P_i transport is regulated by the transfected PTH receptor. The receptors are functionally coupled to the stimulation of adenosine 35 cyclic monophosphate (cAMP) production at both cell surfaces in LLC-PK₁ cells, whereas this response is primarily limited to the basolateral surface in MDCK cells. Immunocytochemistry suggests an apical and basolateral localization of the transfected PTH receptor in LLC-PK₁ cells and only a basolateral localization in MDCK cells. PTH activation of the transfected receptors is not coupled to the regulation of intrinsic P_i transport in either LLC-PK₁ or MDCK cells.