NEUROTENSIN ENHANCES AGONIST-INDUCED CAMP ACCUMULATION IN PC3 CELLS VIA CA2-DEPENDENT ADENYLYL CYCLASE(S)()

A human prostate cancer cell line (PC3) with abundant neurotensin (NT) receptors was used to demonstrate that NT potentiated 3'.5'-cyclic ad enosine monophate (cAMP) accumulation in response to a variety of stim uli, including both direct forskolin (F) and indirect (prostaglandin, (PGE2), isoproterenol (ISO)and cholera toxin (CTx)) activators of aden ylyl cyclase. Several mechanisms were investigated and our results ind icated an effect on the rate of cAMP formation and not on degradation or extrusion. For each stimulus, NT enhanced efficacy without altering EC50. The effect of NT did not involve stimulatory G-protein (Gs)-act ivation or interference with a tonic inhibitory G-protein (Gi)-mediate d inhibition. A similar response was obtained when NT was added with t he stimulus or given as a two minute pulse which was removed prior to addition of stimulus. The potentiating activity disappeared with a t(1 /2) of approximate to 15 min. NT transiently elevated cellular [Ca2+]( i) and its effects on cAMP could be mimicked by [Ca2+](i)-elevating ag ents (uridine triphosphate (UTP), thapsigargin and ionomycin). Bufferi ng cellular [Ca2+](i) with 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-t etraacetic acid acetoxymethyl ester (BAPTA-AM) inhibited cAMP response s to ISO and F in presence and absence of NT. These data support the i dea that NT potentiated cAMP formation in response to a variety of sti muli by facilitating the activation of Ca2+-dependent adenylyl cyclase s. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.