A cooperative action of endothelin-1 with prostaglandin F2α on luteal function in the cow

Human Choroidal Melanocyte Signal Transduction Responses to Various Pharmacological Agents: Focus on Endothelin Receptors

“…10 While the agonist signature of responses of HCOM cells reflected an apparent ET B receptor pharmacology, 6,[24][25][26] this was confirmed by the potent blockade of [ 3 H]-IPs generation by both ET-1 and BQ-3020 by the ET Bselective antagonist, BQ-788, and the lack of effect of the ET A receptor-selective antagonist, BQ-610 ( Figures 3A, 3B). Once again, the potency of BQ-788 in the HCOM cell assays was comparable to that reported for other cell types/tissues, 9,19,[25][26][27] thus, corroborating our pharmacological characterization of the HCOM cell ET receptor system.…”

“…10 Such dual enzymatic activation by ET-1 has been reported for dermal melanocytes where this signal transduction cascade operates to enhance cellular mitogenesis and melanization. 19,[31][32][33][34] It would appear that ET-1 acts as a paracrine endogenous mediator and a melanogen in a number of tissues [28][29][30][31][32][33][34] and, thus, it is likely that in addition to its vasoconstrictor and mitogenic effects, 24-26 ET-1 may have a similar melanogenic role in the choroidal circulation/tissues, and indeed ET-1 has been shown to increase growth and melanization of human uveal melanocytes in culture. 8 It is also quite possible that ET-1, by generating IPs and, thus, mobilizing intracellular Ca 2+ ([Ca 2+ ] i ), [5][6][7]9,10,19 can then cause the release of yet other chemical mediators in and around the melanocytes that also, or in turn, participate in the pigmentation process to maintain the functional integrity of the melanocytes and their important protective roles at the back of the eye.…”

Effect of Intraluteal Injection of Endothelin Type A Receptor Antagonist on PGF2.ALPHA.-induced Luteolysis in the Cow

“…The reason for the discrepancy between the ewe and the cow is not clear. In the ewe, complete luteolysis was induced by an injection of ET-1 followed by a subluteolytic dose of PGF 2α , but plasma P concentration only decreased to the sub-basal levels in the cow [39]. In addition, a recent study using the rabbit model showed that ET-1 alone could induce luteolysis, and this action was completely blocked by injection of ETR-A/B antagonist [38].…”

It Takes Two to Tango but Four for the Finale

“…This led investigators to consider whether other types of cells were missing from the steroidogenic cell cultures (i.e., endothelial cells [18][19][20] and immune cells [21], and the results of many in vitro experiments suggested that the luteolytic effect of PGF 2a likely involved communication among these heterogeneous cells. Support for a critical role of the endothelial cell-derived protein, endothelin 1, in luteal regression was also obtained from in vivo experiments [22][23][24][25].…”