Endothelin receptors and their cellular signal transduction mechanism in human cultured prostatic smooth muscle cells

1. Endothelin (ET) receptors, and their cellular signal transduction mechanism, were characterized in a primary culture of human prostatic smooth muscle cells (HP cell). 2. [(125)I]-ET-1 and [(125)I]-ET-3 binding studies revealed that both ET(A) and ET(B) receptors were present in the HP cells, and the ratio of ET(A) to ET(B) receptors was 1.4:1. 3. Analysis of ET receptor mRNA by reverse transcription-polymerase chain reaction also demonstrated that HP cells express both ET(A) and ET(B) receptors. 4. ET-1 and ET-3 increased intracellular free Ca(2+) concentration ([Ca(2+)](i)) in the HP cells in a concentration-dependent manner. Use of subtype selective antagonists BQ-123 and BQ-788, indicated that both ET(A) and ET(B) receptors were coupled to an increase in [Ca(2+)](i). 5. Pretreatment of the cells with pertussis toxin resulted in a significant but partial attenuation of the [Ca(2+)](i) increase mediated through the ET(A) and ET(B) receptors. However, sensitivity to pertussis toxin (PTX) was significantly different between them. 6. In conclusion, HP cells possess ET(A) and ET(B) receptors. Further, these two endothelin receptor subtypes evoke an increase in [Ca(2+)](i) possibly via the action of different GTP-binding proteins