Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.12 (PKG)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of intracellular cyclic guanosine monophosphate (cGMP) on L-type calcium current (lCa) and contraction of ventricular myocytes enzymatically isolated from guinea pig hearts were investigated to test the hypothesis that cGMP increases contractions along with ICa in these cells. ICa and contractions, elicited every 15 sec, were recorded simultaneously with a whole-cell voltage-clamp method and a video edge-detector, respectively. Cells were superfused with Tyrode's solution (22 degrees C); the pipette solution contained 120 mM potassium aspartate, 30 mM KCl, 4 mM ATP, 5 mM N-(2-hydroxyethyl)piperazine-N-(2-ethanesulfonic acid), 0.01 mM ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and various concentrations of cGMP, which entered the cell interior through the patch electrode. In the presence of 3 nM isoproterenol (ISO) in the bath, ICa was increased 3.2-fold. ICa was further increased by 20% with 30 microM cGMP; cell contractions were also increased by 32%. When ICa was maximal in the presence of 30 nM ISO, cGMP no longer increased ICa or contractions, an indication that the effects of cGMP and ISO were additive. When ICa was increased maximally (4.3-fold) by 100 microM isobutylmethylxanthine, a nonselective phosphodiesterase inhibitor, application of 100 microM cGMP in the pipette decreased ICa by 53% and cell shortening by 64%. Cyclic GMP changed contraction in parallel with ICa in the presence of either ISO or isobutylmethylxanthine. 5'-GMP had no significant effect on ICa or contraction in the presence of ISO or isobutyl-methylxanthine. Cyclic GMP alone, at 30 microM, increased ICa by 25%; this effect on basal ICa was reversed by removal of cGMP from the pipette solution. We conclude that intracellular cGMP had two effects on ICa and contraction, namely, 1) an increase caused by an action on cGMP-inhibited phosphodiesterase and 2) a decrease attributed to activation of cGMP-dependent protein kinase.
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PMID:Biphasic effects of intrapipette cyclic guanosine monophosphate on L-type calcium current and contraction of guinea pig ventricular myocytes. 896 51

Methacholine (MCh) interacted with M(3) muscarinic receptors in rat parotid tissue slices and induced amylase secretion. MCh- and calcimycin-induced exocytosis was completely inhibited by N-[2-(N-(4-chlorocinnamyl)-N-methylaminomethyl)phenyl]-N-[2-hydroxyethyl]-4-methoxybenzenesulfonamide, N(G)-nitro-L-arginine methylester (L-NAME), 1H-(1,2,4)-oxadiazolo[4,3-a]quinoxaline-1-one, and 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide, suggesting that activations of calmodulin (CaM) kinase II, nitric oxide synthase (NOS), and cGMP-dependent protein kinase (PKG) were coupled with the exocytosis. These suggestions were supported by the results that exposure of the slices to MCh induced a rapid increase in these enzyme activities. Western blot analysis showed that neuronal NOS (nNOS) was expressed in isolated parotid acinar cells of rats. To measure nitric oxide (NO) production in response to the stimulation with MCh in real time, the isolated parotid acinar cells had been preloaded with 4,5-diaminofluorescein diacetate and incubated with the agonist. MCh (1 microM) induced a fast increase in 4,5-diaminofluorescein fluorescence, corresponding to an increase in the NO synthesis in the presence of extracellular Ca(2+) but not in the absence of it. When the isolated parotid acinar cells preloaded with L-NAME or 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethylester) were treated simultaneously with MCh, the increase in the fluorescence also was not observed. The MCh-induced increase in the fluorescence was not observed in the cells incubated in the absence of extracellular calcium, showing the importance of Ca(2+) entry from extracellular sites for MCh-induced NOS activation. These results indicate that nNOS is endogenously present in rat parotid acinar cells and that the rapid activation of this enzyme together with those of CaM kinase II and PKG contributes to MCh-induced amylase secretion.
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PMID:Activation of endogenous nitric oxide synthase coupled with methacholine-induced exocytosis in rat parotid acinar cells. 1190 93