Identification of a single (FP) receptor associated with prostanoid-induced Ca2+ signals in Swiss 3T3 cells.
Thus far, the prostanoid FP-receptor has been characterized only on the basis of agonist studies. It is currently classified as a receptor having particular sensitivity to prostaglandin F2 alpha (PGF2 alpha) but with the ability to recognize prostaglandins D2 and E2 (PGD2 and PGE2). We have re-examined this concept by studying second messenger Ca2+ signals to PGF2 alpha, PGD2 and PGE2, and performing radioligand binding studies in Swiss 3T3 cells. The same rank order of potency was obtained for both the Ca2+ transient signal and competition for PGF2 alpha binding sites. The potency rank order, PGF2 alpha > PGD2 > PGE2, was identical to that obtained from functional studies in isolated tissues, such as the cat iris. Additional support for the concept that PGF2 alpha, PGD2, and PGE2 interact with a single receptor to elicit a Ca2+ signal was provided by successive addition studies. Thus, cells pretreated with a supramaximal concentration of PGF2 alpha exhibited little or no response to subsequent administration of PGD2 or PGE2. Likewise, cells pretreated with a large concentration of PGD2 or PGE2 exhibited minimal responsiveness to successive addition of the corresponding alternative prostaglandins. Pretreatment with a maximally effective concentration of PGF2 alpha, PGD2, or PGE2 rendered the cells refractory to the FP-receptor selective agonist fluprostenol, which further supports the hypothesis that Ca2+ transient signals in response to prostanoids in Swiss 3T3 cells are mediated by the FP-receptor. The Ca2+ transient responses to PGF2 alpha, PGD2, and PGE2 also exhibited a similar modest reduction when extracellular Ca2+ was removed. Finally, the DP-receptor antagonist BW A868C did not block the Ca2+ transient response to PGD2, indicating an absence of DP-receptor involvement. Moreover, Ca2+ responses to the thromboxane A2 mimetic U-46619 were unaffected by the TP-antagonist BM 13505, which indicates no involvement of the TP-receptor. These results support the contention that the FP-receptor has particular sensitivity to PGF2 alpha but will also recognize PGD2 and PGE2.
Woodward
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Department of Biological Sciences, Allergan Inc., Irvine, CA 92713-9534.
Lawrence
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D016475:3T3 Cells; D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology*; D006827:Hydantoins / Q000494:pharmacology; D051379:Mice; D015230:Prostaglandin D2 / Q000494:pharmacology*; D011460:Prostaglandins F / Q000494:pharmacology*; D011461:Prostaglandins F, Synthetic / Q000494:pharmacology; D011982:Receptors, Prostaglandin / Q000187:drug effects*; D015290:Second Messenger Systems
D006827:Hydantoins; D011460:Prostaglandins F; D011461:Prostaglandins F, Synthetic; D011982:Receptors, Prostaglandin; C034671:prostaglandin F2alpha receptor; C006326:fluprostenol; C030669:BW 245C; D015232:Dinoprostone; D015230:Prostaglandin D2; D002118:Calcium; C100006:prostaglandin F1