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Pretreatment with 1,25-dihydroxycholecalciferol enhances thyrotropin-releasing hormone- and inositol 1,4,5-trisphosphate-induced release of sequestered Ca2+ in permeabilized GH4C1 pituitary cells. 1992

K Törnquist
Endocrine Research Laboratory, University of Helsinki, Minerva Foundation Institute for Medical Research, Finland.

In GH4C1 cells 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] has been shown to enhance the TRH- and bombesin-induced increase in intracellular Ca2+ ([Ca2+]i). The aim of the present study was to investigate whether this increase in [Ca2+]i could be due to enhanced release of sequestered Ca2+ in cells pretreated with 1,25-(OH)2D3. In digitonin-permeabilized cells, the addition of 10 microM inositol 1,4,5-trisphosphate (IP3) rapidly increased free Ca2+ ([Ca2+]) to 50 +/- 10 nM (mean +/- SE) in cells pretreated with 1 nM 1,25-(OH)2D3 for 24 h, compared with 25 +/- 5 in control cells (P < 0.05). Furthermore, stimulating permeabilized cells with TRH increased [Ca2+]. The increase in control cells was 20 +/- 2, compared with 55 +/- 11 in cells pretreated with 1,25-(OH)2D3 (P < 0.05). Repeated additions of IP3 resulted in an attenuation of the response of [Ca2+] in both control cells and cells pretreated with 1,25-(OH)2D3. However, only the first addition of IP3 resulted in an enhanced increase in [Ca2+] in cells pretreated with 1,25-(OH)2D3 compared with control cells. If the cells were stimulated first with TRH and then with IP3, no difference in the [Ca2+] response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Furthermore, if cells were stimulated with IP3 and then with TRH, no difference in the [Ca2+] response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Stimulating the permeabilized cells with thapsigargin resulted in an increase in [Ca2+]. However, no difference in the response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Addition of GTP or the nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) had no effect on [Ca2+]. The results suggest that 1,25-(OH)2D3 has a modulatory effect on an IP3-sensitive intracellular Ca2+ pool in GH4C1 cells.

UI MeSH Term Description Entries
D010902 Pituitary Gland A small, unpaired gland situated in the SELLA TURCICA. It is connected to the HYPOTHALAMUS by a short stalk which is called the INFUNDIBULUM. Hypophysis,Hypothalamus, Infundibular,Infundibular Stalk,Infundibular Stem,Infundibulum (Hypophysis),Infundibulum, Hypophyseal,Pituitary Stalk,Hypophyseal Infundibulum,Hypophyseal Stalk,Hypophysis Cerebri,Infundibulum,Cerebri, Hypophysis,Cerebrus, Hypophysis,Gland, Pituitary,Glands, Pituitary,Hypophyseal Stalks,Hypophyses,Hypophysis Cerebrus,Infundibular Hypothalamus,Infundibular Stalks,Infundibulums,Pituitary Glands,Pituitary Stalks,Stalk, Hypophyseal,Stalk, Infundibular,Stalks, Hypophyseal,Stalks, Infundibular
D002117 Calcitriol The physiologically active form of vitamin D. It is formed primarily in the kidney by enzymatic hydroxylation of 25-hydroxycholecalciferol (CALCIFEDIOL). Its production is stimulated by low blood calcium levels and parathyroid hormone. Calcitriol increases intestinal absorption of calcium and phosphorus, and in concert with parathyroid hormone increases bone resorption. 1 alpha,25-Dihydroxycholecalciferol,1 alpha,25-Dihydroxyvitamin D3,1, 25-(OH)2D3,1,25(OH)2D3,1,25-Dihydroxycholecalciferol,1,25-Dihydroxyvitamin D3,1 alpha, 25-dihydroxy-20-epi-Vitamin D3,1,25(OH)2-20epi-D3,1,25-dihydroxy-20-epi-Vitamin D3,20-epi-1alpha,25-dihydroxycholecaliferol,Bocatriol,Calcijex,Calcitriol KyraMed,Calcitriol-Nefro,Decostriol,MC-1288,MC1288,Osteotriol,Renatriol,Rocaltrol,Silkis,Sitriol,Soltriol,Tirocal,1 alpha,25 Dihydroxyvitamin D3,1,25 Dihydroxycholecalciferol,1,25 Dihydroxyvitamin D3,1,25 dihydroxy 20 epi Vitamin D3,Calcitriol Nefro,D3, 1 alpha,25-Dihydroxyvitamin,D3, 1,25-Dihydroxyvitamin,D3, 1,25-dihydroxy-20-epi-Vitamin,KyraMed, Calcitriol,MC 1288
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002460 Cell Line Established cell cultures that have the potential to propagate indefinitely. Cell Lines,Line, Cell,Lines, Cell
D002463 Cell Membrane Permeability A quality of cell membranes which permits the passage of solvents and solutes into and out of cells. Permeability, Cell Membrane
D006493 Heparin A highly acidic mucopolysaccharide formed of equal parts of sulfated D-glucosamine and D-glucuronic acid with sulfaminic bridges. The molecular weight ranges from six to twenty thousand. Heparin occurs in and is obtained from liver, lung, mast cells, etc., of vertebrates. Its function is unknown, but it is used to prevent blood clotting in vivo and vitro, in the form of many different salts. Heparinic Acid,alpha-Heparin,Heparin Sodium,Liquaemin,Sodium Heparin,Unfractionated Heparin,Heparin, Sodium,Heparin, Unfractionated,alpha Heparin
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013729 Terpenes A class of compounds composed of repeating 5-carbon units of HEMITERPENES. Isoprenoid,Terpene,Terpenoid,Isoprenoids,Terpenoids
D013973 Thyrotropin-Releasing Hormone A tripeptide that stimulates the release of THYROTROPIN and PROLACTIN. It is synthesized by the neurons in the PARAVENTRICULAR NUCLEUS of the HYPOTHALAMUS. After being released into the pituitary portal circulation, TRH (was called TRF) stimulates the release of TSH and PRL from the ANTERIOR PITUITARY GLAND. Protirelin,Thyroliberin,Abbott-38579,Antepan,Proterelin Tartrate,Proterelin Tartrate Hydrate,Protirelin Tartrate (1:1),Relefact TRH,Stimu-TSH,TRH Ferring,TRH Prem,Thypinone,Thyroliberin TRH Merck,Thyrotropin-Releasing Factor,Thyrotropin-Releasing Hormone Tartrate,Abbott 38579,Abbott38579,Hydrate, Proterelin Tartrate,Prem, TRH,Stimu TSH,StimuTSH,TRH, Relefact,Tartrate Hydrate, Proterelin,Thyrotropin Releasing Factor,Thyrotropin Releasing Hormone,Thyrotropin Releasing Hormone Tartrate
D015544 Inositol 1,4,5-Trisphosphate Intracellular messenger formed by the action of phospholipase C on phosphatidylinositol 4,5-bisphosphate, which is one of the phospholipids that make up the cell membrane. Inositol 1,4,5-trisphosphate is released into the cytoplasm where it releases calcium ions from internal stores within the cell's endoplasmic reticulum. These calcium ions stimulate the activity of B kinase or calmodulin. 1,4,5-InsP3,Inositol 1,4,5-Triphosphate,Myo-Inositol 1,4,5-Trisphosphate,1,4,5-IP3,Myoinositol 1,4,5-Triphosphate

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