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Stimulation of inositol phosphate formation in ros 17/2.8 cell membranes by guanine nucleotide, calcium, and parathyroid hormone
Author(s) -
Cosman Felicia,
Morrow Bruce,
Kopal Marcela,
Bilezikian John P.
Publication year - 1989
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650040317
Subject(s) - parathyroid hormone , inositol phosphate , inositol , phospholipase c , calcium , chemistry , stimulation , gtp' , nucleotide , endocrinology , cyclase , adenylate kinase , medicine , biochemistry , g protein , inositol trisphosphate , enzyme , biology , receptor , organic chemistry , gene
In addition to stimulation of cyclic AMP, parathyroid hormone (PTH) may influence cellular events by utilizing other pathways of hormone action, such as the generation of inositol phosphates (IPs). We sought to examine this potential action of PTH by assessing the formation of inositol phosphates in PTH‐sensitive ROS 17/2.8 cells. The polyphosphoinositides were labeled by growing the cells with [ 3 H]inositol following which cell homogenates were prepared. The nonhydrolyzable guanine nucleotide, GTP γ S, and calcium ion, alone and together, stimulated all three IPs, IP 1 , IP 2 , and IP 3 . IP 1 formation was linear over 30 minutes but IP 2 and IP 3 accumulated more rapidly peaking by 5 minutes for all agonist conditions. The proportion of total P as IP 3 was enhanced when the cells were grown with retinoic acid (1 μM) or when the assay was conducted at pH 4.5. In addition, the lower pH was associated with much more enzyme activity. PTH agonists, bPTH‐(1–84) and bPTH‐(1–34), both caused a small but significant stimulation of IP 3 formation. When bPTH‐(1–84), and the analog bPTH‐(3–34)amide, that inhibits PTH‐mediated adenylate cyclase activity were present together, there was additive stimulation of IP 3 formation compared with that with either agent alone. The results demonstrate that inositol phosphate formation can be stimulated directly in a membrane preparation of ROS cells by GTP γ S, calcium ion, and PTH and that the enzyme mediating this activity, phospholipase C, is regulated by a guanine nucleotide binding protein.