XXXX vasopressin triggers intracellular calcium release, a calcium-activated potassium current and exocytosis in identified @entity35 corticotropes.

@entity671 @entity141 @entity3006 @entity35 @entity369
@entity369 vasopressin (AVP) stimulates the secretion of ACTH from pituitary corticotropes. We investigated the action of AVP in single corticotropes of male @entity35 . Corticotropes were identified with the reverse hemolytic plaque assay using antibodies against ACTH. Using the whole-cell recording technique in conjunction with the fluorescent @entity141 indicator, indo-1 to measure the concentration of cytosolic free @entity141 ([ @entity141 ]i), we show that AVP triggers a transient and plateau pattern of @entity141 signal. The [ @entity141 ]i elevation activates the apamin-sensitive @entity141 -activated K+ current, which, in turn, causes membrane hyperpolarization. The @entity141 signal can be elicited in the absence of extracellular @entity141 and is mimicked by intracellular @entity671 (IP3). Both @entity3006 -beta-S and heparin inhibit the AVP response. Thus, AVP triggers intracellular @entity141 release from the (IP3)-sensitive store via a GTP binding protein-coupled phosphoinositide pathway. Using the high temporal resolution capacitance measurement to detect exocytosis in single corticotropes, we show that a burst of exocytosis is evoked during the AVP-triggered [ @entity141 ]i elevation. Exocytosis can also be triggered when @entity141 is released directly from the IP3-sensitive store via flash photolysis of caged IP3. We conclude that AVP-stimulated ACTH secretion in @entity35 corticotrophs is closely coupled to intracellular @entity141 release from the IP3-sensitive store.
