PT  - JOURNAL ARTICLE
AU  - Semler, D E
AU  - Ohlstein, E H
AU  - Nambi, P
AU  - Slater, C
AU  - Stern, P H
TI  - Endothelin-1-evoked calcium transients in UMR-106 osteoblastic osteosarcoma cells are mediated through endothelin-A and endothelin-B receptors.
DP  - 1995 Mar 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1052--1058
VI  - 272
IP  - 3
4099  - http://jpet.aspetjournals.org/content/272/3/1052.short
4100  - http://jpet.aspetjournals.org/content/272/3/1052.full
SO  - J Pharmacol Exp Ther1995 Mar 01; 272
AB  - Endothelin (ET) receptor subtypes involved in the modulation of intracellular calcium were studied in UMR-106 osteoblastic osteosarcoma cells. Calcium signaling in UMR-106 cells in suspension was determined with fluo-3-acetoxymethylester fluorescent dye. ET-1 and the ETB-selective agonist sarafotoxin 6c (S6c) elicited rapid calcium transients. Maximally effective concentrations of the ETA-selective antagonist BQ-123 [Cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu)] attenuated ET-1-evoked calcium transients by only 50%. BQ-123 had no effect on S6c-stimulated transients. ET-1 and S6c showed homologous desensitization on repeated administration. Pretreatment with ET-1 completely eliminated S6c-evoked calcium transients, whereas S6c pretreatment only partially (50%) attenuated the calcium transient evoked by ET-1. Joint pretreatment with S6c and BQ-123 or pretreatment with the ETA/ETB nonselective antagonist PD-142893 (Ac-D-diphenylalanine-Leu-Asp-Ile-Ile-Trp) eliminated the ET-1-stimulated calcium transient. These cells display both ETA and ETB receptors (60:40), as demonstrated by saturation binding experiments with [125I] ET-1 and the ETB specific agonist, [125I] IRL-1620 (Suc [Glu9, Ala11,15] endothelin-1 [8-21]). This was further confirmed by competition binding experiments using [125I] ET-1 and subtype-selective ligands S6c and BQ-123. These data indicate that ET-1 interacts with both ETA and ETB receptors to elicit calcium transients in UMR-106 osteoblastic osteosarcoma cells.