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

Parathyroid hormone (PTH) inhibits renal proximal tubular phosphate (Pi) and bicarbonate reabsorption by regulating the activity of apical Na/Pi 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 Pi transport is regulated by the transfected PTH receptor. The receptors are functionally coupled to the stimulation of adenosine 3':5' 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 Pi transport in either LLC-PK1 or MDCK cells.