The activation of protein kinase C prevents PGE2-induced inhibition of AVP-dependent cAMP accumulation in the rat outer medullary collecting tubule

Abstract

Previous studies have demonstrated that prostaglandin E2 (PGE2) inhibits arginine vasopressin-(AVP)dependent adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in microdissected rat outer medullary collecting tubules (OMCD), by a mechanism unrelated to the inhibition of cAMP synthesis. The potential role of the activation of protein kinase C (PKC) to explain the negative regulation elicited by PGE2 was investigated in this study. Single OMCD samples were pre-incubated (10 min, 30 degrees C) in the presence or absence of either activators of PKC, phorbol 12-myristate 13-acetate (PMA), 1-oleoyl-2-acetyl-glycerol (OAG), dioctanoylglycerol (DOG) or an inhibitor of PKC, staurosporine (SSP). These compounds were present also with the agonists tested during the incubation period (4 min, 35 degrees C). In contrast to PGE2, activators of PKC did not decrease AVP-dependent cAMP accumulation (mean +/- SEM): 1 nM AVP = 47.1 +/- 6.8 fmol.mm-1 x 4 min-1; AVP+0.3 microM PGE2 = 20.1 +/- 2.7, P < 0.01 versus AVP; AVP + 10 nM PMA = 42.0 +/- 4.7, NS versus AVP; AVP + 50 micrograms/ml OAG = 44.1 +/- 4.8. NS versus AVP, N = 5 experiments. However, 10 nM PMA prevented PGE2-induced inhibition: AVP + PGE2 = 44.2 +/- 3.5% of the response to AVP and 90.3 +/- 3.2% without and with PMA respectively, N = 16. Similar results were obtained with either 50 micrograms/ml OAG or 25 micrograms/ml DOG (AVP + PGE2 + OAG = 92.9 +/- 6.6% of the response to AVP, N = 8; AVP + PGE2 + DOG = 94.1 +/- 5.3%, N = 7).(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of mRNAs Encoding Ca2+-inhibitable Adenylyl Cyclases along the Renal Tubule

“…Similar results were obtained in the presence of Ro 20 -1724 (32). These data therefore indicate that carbachol does not regulate cAMP pathway in the AVP-sensitive cells of the rat OMCD.…”

“…This observation suggests that type VI adenylyl cyclase mRNA is functionally expressed in the principal cells, an hypothesis supported by the following arguments. (i) As we observed with Ca 2ϩ ionophores, the level of type VI AC inhibition in different cells is correlated with the rise of [Ca 2ϩ ] i achieved with different concentrations of agonists or ionophores (13,35 (32), a result in agreement with the lack of regulation of this kinase on type VI AC (36,37). The presence of a Ca 2ϩ -inhibitable AC in the principal cells is also supported by the comparison between the properties of regulation of the cAMP content known in the rat OMCD and those that result from the presence of the Ca 2ϩ -inhibitable type VI AC in different cell lines.…”

“…Indeed, different studies allowed the definition of several properties of PGE 2 -induced inhibition of AVP-dependent cAMP accumulation. This effect is insensitive to pertussis toxin, dependent on extracellular Ca 2ϩ , cumulative to the G i -mediated inhibition elicited by ␣ 2 -adrenergic agonists in the same cell type, and is linked to the increase of [Ca 2ϩ ] i and/or to the capacitive Ca 2ϩ entry elicited by PGE 2 in the principal cells (30,32). It is noteworthy that these properties of regulation of cAMP levels are identical to those described in different cells that express type VI AC mRNA (4,5,9,35).…”

Extracellular calcium antagonizes forskolin-induced aquaporin 2 trafficking in collecting duct cells

“…This mechanism may explain the reduction in cAMP levels. Alternatively Ca 2+ -dependent increase in [Ca 2+ ] i can impair cAMP accumulation by an increase in cAMP hydrolysis, through a Ca 2+ -mediated process [33,34].…”

“…As [Ca 2+ ] i regulates cAMP levels in many cell types through interaction of calcium on cAMP synthesis and/or hydrolysis [33,34], we first analyzed whether a forskolin-elicited increase in cAMP levels is influenced by Ca 2+ o . When CD8 cells were stimulated with forskolin (10 −4 mol/L, 15 minutes), cAMP levels increased by 14.79 ± 1.6-fold (N = 18) with respect to control cells (Fig.…”