Parathyroid hormone (PTH) and its closely related peptide, PTHrP, share the same receptor, PTHR. LLC-PK1 cells are porcine renal epithelial cells which do not normally express PTHR. The present-invention provides stably transfected LLC-PK1 cells which express human PTHR. Also provided are methods for determining whether a compound of interest is an agonist or antagonist of a Gs or Gq protein coupled receptor.