Cyclic nucleotides concentrations in the canine heart with regional ischemia. The role of cyclic AMP in ventricular fibrillation and the effect of dibutyryl cyclic AMP.

1984 ◽  
Vol 48 (3) ◽  
pp. 247-252 ◽  
Author(s):  
MASATOSHI UKAI ◽  
KOUICHI OGAWA
Keyword(s):  
Ventricular Fibrillation ◽  
Cyclic Amp ◽  
Cyclic Nucleotides ◽  
Canine Heart ◽  
Dibutyryl Cyclic Amp ◽  
Regional Ischemia

scholarly journals The Role of Cyclic Nucleotides in the CNS

1977 ◽  
Vol 4 (3) ◽  
pp. 151-195 ◽  
Author(s):  
John W. Phillis
Keyword(s):  
Cyclic Amp ◽  
Synaptic Transmission ◽  
Cyclic Gmp ◽  
Adenosine Receptor ◽  
Cyclic Nucleotides ◽  
Phosphodiesterase Inhibitors ◽  
Adenosine Uptake ◽  
Injection Techniques ◽  
Firm Basis

SUMMARY:On the basis of the information presented in this review, it is difficult to reach any firm decision regarding the role of cyclic AMP (or cyclic GMP) in synaptic transmission in the brain. While it is clear that cyclic nucleotide levels can be altered by the exposure of neural tissues to various neurotransmitters, it would be premature to claim that these nucleotides are, or are not, essential to the transmission process in the pre- or postsynaptic components of the synapse. In future experiments with cyclic AMP it will be necessary to consider more critically whether the extracellularly applied nucleotide merely provides a source of adenosine and is thus activating an extracellularly located adenosine receptor, or whether it is actually reaching the hypothetical sites at which it might act as a second messenger. The application of cyclic AMP by intracellular injection techniques should minimize this particular problem, although possibly at the expense of new difficulties. Prior blockade of the adenosine receptor with agents such as theophylline or adenine xylofuranoside may also assist in the categorization of responses to extracellularly applied cyclic AMP as being a result either of activation of the adenosine receptor or of some other mechanism. Ultimately, the development of highly specific inhibitors for adenylate cyclase should provide a firm basis from which to draw conclusions about the role of cyclic AMP in synaptic transmission. Similar considerations apply to the actions of cyclic GMP and the role of its synthesizing enzyme, guanylale cyclase.The use of phosphodiesterase inhibitors in studies on cyclic nucleotides must also be approached with caution. The diverse actions of many of these compounds, which include calcium mobilization and block of adenosine uptake, could account for many of the results that have been reported in the literature.

scholarly journals Receptor-mediated gonadotropin action in the ovary. Regulatory role of cyclic nucleotide phosphodiesterase(s) in intracellular adenosine 3′:5′-cyclic monophosphate turnover and gonadotropin-stimulated progesterone production by rat ovarian cells

1979 ◽  
Vol 180 (1) ◽  
pp. 201-211 ◽  
Author(s):  
Salman Azhar ◽  
K. M. Jairam Menon
Keyword(s):  
Cyclic Amp ◽  
Kinase Activity ◽  
Phosphodiesterase Inhibitors ◽  
Protein Kinase Activity ◽  
Dibutyryl Cyclic Amp ◽  
Steroid Production ◽  
Progesterone Production ◽  
Ovarian Cells ◽  
Cyclic Amp Accumulation

The regulatory role of cyclic nucleotide phosphodiesterase(s) and cyclic AMP metabolism in relation to progesterone production by gonadotropins has been studied in isolated rat ovarian cells. Low concentrations of choriogonadotropin (0.4–5ng/ml) increased steroid production without any detectable increase in cyclic AMP, when experiments were carried out in the absence of phosphodiesterase inhibitors. The concentration of choriogonadotropin (10ng/ml) that stimulated progesterone synthesis maximally resulted in a minimal increase in cyclic AMP accumulation and choriogonadotropin binding. Choriogonadotropin at a concentration of 10ng/ml and higher, however, significantly stimulated protein kinase activity and reached a maximum between 250 and 1000ng of hormone/ml. Higher concentrations (50–2500ng/ml) of choriogonadotropin caused an increase in endogenous cyclic AMP, and this increase preceded the increase in steroid synthesis. Analysis of dose–response relationships of gonadotropin-stimulated cyclic AMP accumulation, progesterone production and protein kinase activity revealed a correlation between these responses over a wide concentration range when experiments were performed in the presence of 3-isobutyl-1-methylxanthine. The phosphodiesterase inhibitors papaverine, theophylline and 3-isobutyl-1-methylxanthine each stimulated steroid production in a dose-dependent manner. Incubation of ovarian cells with dibutyryl cyclic AMP or 8-bromo cyclic AMP mimicked the steroidogenic action of gonadotropins and this effect was dependent on both incubation time and nucleotide concentration. Maximum stimulation was obtained with 2mm-dibutyryl cyclic AMP and 8-bromo cyclic AMP, and this increase was close to that produced by a maximally stimulating dose of choriogonadotropin. Other 8-substituted derivatives such as 8-hydroxy cyclic AMP and 8-isopropylthio cyclic AMP, which were less susceptible to phosphodiesterase action, also effectively stimulated steroidogenesis. The uptake and metabolism of cyclic [3H]AMP in ovarian cells was also studied in relation to steroidogenesis. When ovarian cells were incubated for 2h in the presence of increasing concentrations of cyclic [3H]AMP, the radioactivity associated with the cells increased almost linearly up to 250μm-cyclic [3H]AMP concentration in the incubation medium. The 3H label in the cellular extract was recovered mainly in the forms ATP, ADP, AMP, adenosine and inosine, with cyclic AMP accounting for less than 1% of the total tissue radioactivity. Incubation of cyclic AMP in vitro with ovarian cells resulted in a rapid breakdown of the nucleotide in the medium. The degradation products in the medium have been identified as AMP, adenosine and inosine. The rapid degradation of cyclic AMP by phosphodiesterase(s) makes it difficult to correlate changes in cyclic AMP concentrations with steroidogenesis. These observations thus provide an explanation for the previously observed lack of cyclic AMP accumulation under conditions in which low doses of choriogonadotropin stimulated steroidogenesis without any detectable changes in cyclic AMP accumulation.

scholarly journals Evidence against an involvement of cyclic nucleotides in the induction of βcyanin synthesis by cytokinins

1975 ◽  
Vol 146 (2) ◽  
pp. 333-337 ◽  
Author(s):  
D C Elliott ◽  
A W Murray
Keyword(s):  
Cyclic Amp ◽  
Cyclic Nucleotides ◽  
Red Light ◽  
Phosphodiesterase Activity ◽  
Dibutyryl Cyclic Amp ◽  
Purine Bases ◽  
Cyclic Amp Phosphodiesterase ◽  
Induction Process ◽  
Wide Range

1. A wide range of purine bases, nucleosides and cyclic nucleotides were shown to induce βcyanin synthesis in Amaranthus seedlings. 2. The induction of pigment by benzyladenine, dibutyryl cyclic AMP or cyclic AMP was not potentiated by aminophylline. Aminophylline was shown to inhibit Amaranthus cyclic AMP phosphodiesterase activity. 4. Incubation of seedlings with aminophylline inhibited the conversion of 6-[G-3H]benzyladenine into presumed 9- and 7-glucosylbenzyladenine. 5. Induction of βcyanin synthesis by 6-benzyladenine or by exposure to red light was not accompanied by changes in the total cyclic AMP content in seedlings. 6. It is concluded that the inducers tested act as cytokinin analogues; no evidence was obtained to support cyclic AMP as an intermediate in the induction process.

Effects of Dibutyryl Cyclic AMP and Papaverine on Intrahepatocytic Bile Acid Transport Role of Vesicle Transport

1993 ◽  
Vol 28 (9) ◽  
pp. 833-838 ◽  
Author(s):  
M. Hoshino ◽  
T. Ohiwa ◽  
T. Hayakawa ◽  
Y. Kamiya ◽  
A. Tanaka ◽  
...  
Keyword(s):  
Bile Acid ◽  
Cyclic Amp ◽  
Vesicle Transport ◽  
Acid Transport ◽  
Dibutyryl Cyclic Amp ◽  
Bile Acid Transport

Regulation of Pancreatic Acinar Function: Effects of Cyclic AMP, Dibutyryl Cyclic AMP, and Theophylline in Vitro

1974 ◽  
Vol 52 (4) ◽  
pp. 780-785 ◽  
Author(s):  
T. H. Brian Haig
Keyword(s):  
Protein Synthesis ◽  
Cyclic Amp ◽  
Digestive Enzymes ◽  
Amylase Secretion ◽  
Dibutyryl Cyclic Amp ◽  
Rat Pancreas ◽  
Rule Out

The role of cyclic AMP in the regulation of pancreatic acinar function has been assessed by measuring the effects of exogenous cyclic AMP, dibutyryl cyclic AMP, and theophylline on protein synthesis and amylase secretion. The rate at which slices of rat pancreas incorporated leucine into protein did not change as a consequence of treatment with either cyclic AMP or dibutyryl cyclic AMP, nor did the slices alter their rate of amylase secretion. Moreover, theophylline did not enhance the ability of submaximal doses of pancreozymin to stimulate amylase secretion or to suppress protein synthesis. These results fail to demonstrate that cyclic AMP regulates either the synthesis or secretion of pancreatic digestive enzymes but they do not rule out the possibility.

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