3 research outputs found
Biochemical characterization of soluble nucleotide pyrophosphatase/phosphodiesterase activity in rat serum
Biochemical properties of nucleotide pyrophosphatase/phosphodiesterase (NPP) in rat serum have been described by assessing its nucleotide phosphodiesterase activity, using p-nitrophenyl-5-thymidine monophosphate (p-Nph-5-TMP) as a substrate. It was demonstrated that NPP activity shares some typical characteristics described for other soluble NPP, such as divalent cation dependence, strong alkaline pH optimum (pH 10.5), inhibition by glycosaminoglycans, and K (m) for p-Nph-5-TMP hydrolysis of 61.8 +/- A 5.2 mu M. In order to characterize the relation between phosphodiesterase and pyrophosphatase activities of NPP, we have analyzed the effects of different natural nucleotides and nucleotide analogs. ATP, ADP, and AMP competitively inhibited p-Nph-5-TMP hydrolysis with K (i) values ranging 13-43 mu M. Nucleotide analogs, alpha,beta-metATP, BzATP, 2-MeSATP, and dialATP behaved as competitive inhibitors, whereas alpha,beta-metADP induced mixed inhibition, with K (i) ranging from 2 to 20 mu M. Chromatographic analysis revealed that alpha,beta-metATP, BzATP, and 2-MeSATP were catalytically degraded in the serum, whereas dialATP and alpha,beta-metADP resisted hydrolysis, implying that the former act as substrates and the latter as true competitive inhibitors of serum NPP activity. Since NPP activity is involved in generation, breakdown, and recycling of extracellular adenine nucleotides in the vascular compartment, the results suggest that both hydrolyzable and non-hydrolyzable nucleotide analogs could alter the amplitude and direction of ATP actions and could have potential therapeutic application
Long-term intermittent feeding restores impaired GR signaling in the hippocampus of aged rat
Diminished glucocorticoid signaling is associated with an age-related
decline in hippocampal functioning. In this study we demonstrate the
effect of intermittent, every other day (EOD) feeding on the
glucocorticoid hormone/glucocorticoid receptor (GR) system in the
hippocampus of middle-aged (18-month-old) and aged (24-month-old) Wistar
rats. In aged ad libitum-fed rats, a decrease in the level of total GR
and GR phosphorylated at Ser(232) (pGR) was detected. Conversely, aged
rats subjected to EOD feeding, starting from 6 months of age, showed an
increase in GR and pGR levels and a higher content of hippocampal
corticosterone. Furthermore, prominent nuclear staining of pGR was
observed in CM pyramidal and DG granule neurons of aged EOD-fed rats.
These changes were accompanied by increased Sglc-1 and decreased GFAP
transcription, pointing to upregulated transcriptional activity of GR.
EOD feeding also induced an increase in the expression of the
mineralocorticoid receptor. Our results reveal that intermittent feeding
restores impaired GR signaling in the hippocampus of aged animals by
inducing rather than by stabilizing GR signaling during aging. (C) 2015
Elsevier Ltd. All rights reserved.Ministry of Education, Science and Technological Development of the
Republic of Serbia {[}ON173056, ON173008]; NIH {[}R03AG046216