Vasopressin V1a receptor signaling in a rat choroid plexus cell line

A new cell line was derived from primary culture of rat choroid plexus (RCP ) by immortalization with the TSOri minus adenovirus. The selected clone ex pressed vasopressin Via receptors at a density of 64,000 sites per cell, an d a K-d of 7.2 nM. Addition of vasopressin to the RCP cells induced a trans ient calcium peak comparable to Via receptor signalling in different expres sion systems. This [Ca2+](i) increase was dose-dependent with an EC50 of 22 nM vasopressin. Similar [Ca2+](i) increase was elicited by addition of ser otonin, angiotensin II, endothelin-1, and bradykinin, Heterologous desensit ization of Via receptor was observed in RCP cells exposed to the phorbol es ter PMA or following stimulation of other receptors coupled to the phosphoi nositide pathway. Positive immunolabelling with Factor VIII, Flt1 and CD 34 antibodies suggests that this new RCP cell line originated from endothelia l cells of rat choroid plexus. (C) 2000 Academic Press.