(WPBs) that release their content into the vascular lumen in response to specific agonists
that raise intracellular Ca 2+ or cAMP. We have previously shown that cAMP-mediated WPB
release is dependent on protein kinase A (PKA) and involves activation of the small GTPase
RalA. Here, we have investigated a possible role for another PKA-independent cAMP-
mediated signaling pathway in the regulation of WPB exocytosis, namely the guanine …