Parathyroid hormone stimulates formation of inositol phosphates in a membrane preparation of canine renal cortical tubular cells

Recent studies have shown that, in addition to its well-known action to stimulate adenylate cyclase activity, parathyroid hormone (PTH) may stimulate the inositol phosphate second messenger system in its target tissues, bone and kidney. We have developed a membrane preparation of canine renal cortex to test this hypothesis. We also have examined the potential role of guanine nucleotides on the formation of inositol phosphates (IPs) in this tissue. Collagenase-dispersed tubules were labeled with [³H]inositol, and membranes containing labeled phospholipase C (PLC) substrates ([³H]phosphatidyl inositol, [³H]phosphatidylinositol monophosphate, and [³H]phosphatidylinositol bisphosphate) were prepared. bPTH-(1–34) (100 nM) rapidly increased levels of all measured [³H]IPs (IP₁, IP₂, and IP₃) 1.6–1.7-fold within the first 30 s of stimulation. The half-maximal concentration for the response to bPTH-(1–34) was approximately 8 nM. GTPγS (100 μM), a nonhydrolyzable analog of GTP, also increased levels of the three [³H]IPs (1.8 to 2.8-fold). The half-maximal concentration for the response to GTPγS was approximately 30 μM. In the presence of GTPμS, bPTH-(1–34) increased levels of IPs by up to 2.7 times more than GTPγS alone. The results indicate that bPTH-(1–34) can stimulate the formation of inositol phosphates in the kidney and suggest that PTH may activate a receptor coupled to this effect through a guanine nucleotide regulatory protein.