Increased RNA synthesis in nuclei isolated from rat liver tissue slices incubated with cyclic adenosine 3′,5′-monophosphate or glucagon

Biochemical aspects of orthodontic tooth movement. I. Cyclic nucleotide and prostaglandin concentrations in tissues surrounding orthodontically treated teeth in vivo

The objective of this study was to extract and assay cyclic nucleotides and prostaglandins from tissues surrounding orthodontically treated canines in cats. Seven groups of three to five female cats were treated by 80 g tipping force to one maxillary canine for 0 to 28 days. Tissue samples were removed from sites of compression and tension around treated teeth, and from the corresponding control sites. Cyclic nucleotides and prostaglandins were simultaneously extracted by a solvent system at 0 to -5 degrees C. A portion of the aqueous fraction was used for cAMP assay by a binding protein method; cGMP was purified by column chromatography and measured by radioimmunoassay. The solvent fraction was dried, reconstituted with assay buffer, and each of the prostaglandins measured by radioimmunoassay. Analysis of variance showed no significant differences between summary control and treated sites at each of the time periods studied. However, when interactions at secondary and tertiary levels were considered (such as tension and compression, position [apical-gingival sites] of tissue sample, and jaws), significant differences were found in PGE, cAMP, and PGF2 alpha values. These results demonstrate that alterations in the levels of each of these substances in tissues surrounding teeth may be brought about by long-term applications of orthodontic force in vivo. The method of tissue sampling, however, does not permit measurement of the levels of these substances in target cells alone, thus diluting the acute response that may have occurred in these cells.

Enhancement by GTP of cAMP binding to hepatic nuclei and cytosol

In the present study we have demonstrated specific binding of 3H-labeled adenosine 3',5'-cyclic monophosphate (cAMP) to a nuclear extract from rat liver. GTP, GDP, and low concentrations of ATP and ADP increased nuclear binding of [3H]cAMP, and AMP inhibited [3H]cAMP binding. Photoaffinity labeling studies employing [32P]cAMP revealed four nuclear binding proteins [relative molecular weight (Mr) 36,000, 49,000, 54,000 and 57,000]. Unlabeled cAMP decreased [32P]cAMP binding to all four proteins, whereas GTP increased binding to the 57,000 protein. We also observed specific binding of [3H]cAMP in the liver cytosol, which was stimulated by GTP but not by ADP or ATP. Photoaffinity labeling studies of the cytosol in the absence of unlabeled nucleotides revealed three cAMP-binding proteins (Mr 36,000, 49,000, and 54,000). Unlabeled cAMP inhibited binding of [32P]cAMP to all three proteins, whereas in the presence of GTP there was binding of [32P]cAMP to a Mr 57,000 protein. Using DEAE-cellulose, we isolated from the nuclear extract and cytosol a cAMP-binding protein that responded to GTP with an increase in cAMP binding but was unaffected by GDP, ATP, ADP, and AMP. Guanosine imidodiphosphate did not affect cAMP binding, suggesting that the stimulatory effect of GTP may be mediated by phosphorylation. We speculate that alterations in intracellular GTP in vivo may modulate the binding of cAMP to a protein in the nucleus and cytosol.

Effect of glucagon on alanine 2-oxoglutarate aminotransferase

Alanine-2-oxoglutarate aminotransferase activity in mouse liver is stimulated by the intravenous injection of glucagon. The stimulation is abolished by pretreatment with actinomycin D indicating that the increased activity is probably due to new enzyme formation. Administration of dibutyryl cyclic AMP, isoproterenol, an activator of adenyl cyclase and theophylline, an inhibitor of phosphodiesterase also increases the enzyme activity suggesting the involvement of cyclic AMP in glucagon-mediated increase of enzyme activity.

Cyclic AMP in dental and periodontal tissues during tooth eruption in kittens

Cyclic adenosine 3',5'-monophosphate (cAMP) concentrations and cellular distribution were studied in dental and periodontal tissues during tooth eruption in kittens. Although the mean levels of cAMP around developing teeth were similar in all the tissue samples, there were marked differences in cAMP stainability of tissues apical and occlusal to the erupting teeth.

Cyclic nucleotide levels in the perfused rat heart subjected to hypoxia

Isolated rat hearts were subjected to hypoxic perfusion on a recirculating Langendorff apparatus. Following a 30-min-period of aerobic stabilization the hearts were perfused for 30 min with media equilibrated with 84% N2, 12%O2 and 4% CO2. At the end of the hypoxic period myocardial concentrations of cyclic AMP and cyclic GMP were determined by radioimmunoassay. Exposure to hypoxia resulted in a significant increase in cyclic AMP (p less than 0.01) and a decrease in cyclic GMP (p less than 0.05) as compared to hearts perfused for 60 min with media gassed with 96% O2. 4% CO2.

Stimulation by N6,O2'-dibutyrul andenosine 3',5'-cyclic monophosphate of RNA and DNA synthesis and of cell proliferation of rat hepatocytes in primary tissue culture

The effects of DBcAMP in doses from 1.5 x 10(-8) to 1.5 x 10(-3) M on the compartmental apparent surface area (ASA) and (5(-3H)uridine radioactivity concentration (URC), (methyl-3H)thymidine labelling index per 1 hour ([Me-3H]Tdr LI/h) and per cent mitotic index (MI%) and colchicine metaphase index (CMI%) of young rat differentiated hepatocytes in primary tissue culture were investigated by morphometric and radioautographie methods. In these cells DBcAMP was found to elicit: (1) progressive increments in the ASA of nucleoli, karyoplasm and cytoplasm; (2) peak increases in nucleolar URC at 1.5 x 10(-8) and 10(-5) M, but a slight decrease at 1.5 x 10(-3) M; (3) singificant increments in karyoplasmic and total nuclear URC at all doses, except at 1.5 x 10(-6) and 10(-4) M, when such parameters remained at control levels; (4) steady and progressive increases in cytoplasmic and total cell URC values; (5) marked increments in (Me-3H)Tdr LI/h, MI% and CMI% up to the dose of 1.5 x 10(-4) M, but at 1.5 x 10(-3) M these parameters were found to be either much less enhanced or to approach closely to control values. cAMP in doses from 1.5 x 10(-8) to 10(-4) M also markedly incremented the in vitro hepatocyte CMI%, while having a lesser stimulatory effect at 1.5 x 10(-3)M. Finally of the various possible metabolites of DBcAMP administered at 1.5 x 10(-8) M to liver cultures, N6- and O2'-MBcAMP and, again, cAMP significantly increased the CMI%, of cultured hepatocytes, whereas 5'-AMP, adenosine and allantoin had no significant effect and Na-butyrate slightly decreased it. The present observations strengthen the hypothesis that cAMP and its butyrated derivatives, by possibly amplifying the template activity of the liver chromatin, accelerate the flow of differentiated primary young rat hepatocytes into the various stages of the mitotic cell cycle.

Effect of adenosine 3',5'-cyclic monophosphate on the RNA and DNA synthesis and cell proliferation of rat hepatocytes in primary culture: a radioautographic study

The effect of a 24-h treatment with various doses (from 1.5-10-minus 8 to 3.0-10-minus 3 M) of adenosine 3',5'-cyclic monophospahte (cAMP) on morphometric parameters, [5--3H]uridine radioactivity concentration (URC), [methyl--3H]thymidine [Me--3H]-Tr) labelling index per hour (L.I./h) and per cent mitotic index (M.I.%) of young rat differentiated hepatocytes in primary tissue culture were investigated by morphometric and radioautographic methods. In such cells cAMP was found to induce: (1) a reduction of the apparent surface area (ASA) of total nucleoli, karyoplasm and cytoplasm; (2) significant increases in URC of all the subcellular compartments at all the dosages employed (only cAMP at 1.5-10-minus 8 M did not change karyoplasmic and cytoplasmic URC values); (3) marked increments in [Me--3H]Tdr L.I./h and M.I.% from the lowest dose up to 1.5-10-minus 4 M; at higher doses the L.I./h and M.I.% were less stimulated or approached control values. In cultured rat hepatocytes, adenosine-5'-phosphate (5'-AMP) (1.5-10-minus 4 M per 24 h) increased the karyoplasmic and total cell ASA, the lone total nucleolar URC and both the L.I./h and M.I.%. However, these metabolic effects were significantly less intense than those elicited by isomolar cAMP. Theophylline (Theo) (5.5-10-minus 5 M per 24 h) reduced the in vitro rat hepatocyte total nucleolar ASA but affected neither other morphometric nor any of the URC values. The same dose of Theo plus cAMP (1.5-10-minus M) had no morphometric effect but significantly increased the URC values of all primary rat hepatocyte compartments. Actinomycin D (DAct) (0.1 mug/ml per 24 h) plus cAMP (1.5-10-minus 4 M) decreased the cultured rat hepatocyte total nucleolar ASA but enlarged that of karyoplasm and cytoplasm and, further, markedly curtailed all the compartmental URC values. These data support the hypothesis that cAMP amplified the template activity of the liver chromatin and accelerates the flow of differentiated primary young rat hepatocytes into the various stages of the mitotic cell cycle.