Search PubMed⌕ Search
Home/Archive/PubMed

PubMed · 14082

Gastric secretion.

G Sachs·J G Spenney·W S Rehm
View original source ↗Export metadata ↓

Abstract

This review has attempted to cover some of the findings that have been made in the mechanism of gastric secretion in recent years. It is hard to offer any firm conclusions, whether at the level of stimulus, metabolism, or the terminal process of secretion. However, some generalizations may be possible. At least amphibian gastric secretion is stimulated by cAMP as a second messenger, with histamine presumably acting as the primary messenger. The resultant metabolic change is due largely to a direct stimulation of catabolism, which in dog appears to be the metabolism of hexose, through the glycolytic process, the hexose monophosphate shunt, and the Krebs' cycle with cytoplasmic reduction and mitochondrial oxidation of pyridine nucleotides. No evidence could be obtained for changes in high energy phosphate or for lipolysis. One would expect gastric mucosal membranes during secretion to contain an anion-restricted electrogenic H+ pump, but they in fact contain an ATPase stimulated by monovalent cations and are insensitive to ouabain. In addition, hog or dog gastric membranes have the vectorial properties of H+ absorption, Rb+ extrusion, and ANS fluorescence enhancement with the addition of ATP, as well as protein phosphorylation by 32P dependent on a K+ gradient.

Explore related subjects

3',5'-Cyclic-AMP PhosphodiesterasesAcetylcholineAdenosine TriphosphatasesAdenylyl CyclasesAmphibiansAnimalsBiological Transport, ActiveCalciumCell FractionationCyclic AMPGastric JuiceGastric MucosaGastrinsGuanylate CyclaseHistamineMammalsMembrane PotentialsProtein KinasesProtonsReceptors, Cell SurfaceReceptors, CholinergicReceptors, HistamineReceptors, Histamine H2Journal ArticleResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.Review

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

G Sachs, J G Spenney, W S Rehm. 1977. Gastric secretion.. https://pubmed.ncbi.nlm.nih.gov/14082/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1998

Insulin-induced phosphorylation and activation of phosphodiesterase 3B in rat adipocytes: possible role for protein kinase B but not mitogen-activated protein kinase or p70 S6 kinase.

Insulin stimulation of adipocytes results in serine phosphorylation/activation of phosphodiesterase 3B (PDE 3B) and activation of a kinase that phosphorylates PDE 3B in vitro, key events in the antilipolytic action of this hormone. We have investigated the role for p70 S6 kinase, mitogen-activated protein kinases (MAP kinases), and protein kinase B (PKB) in the insulin signaling pathway leading to phosphorylation/activation of PDE 3B in adipocytes. Insulin stimulation of adipocytes resulted in increased activity of p70 S6 kinase, which was completely blocked by pretreatment with rapamycin. However, rapamycin had no effect on the insulin-induced phosphorylation/activation of PDE 3B or the activation of the kinase that phosphorylates PDE 3B. Stimulation of adipocytes with insulin or phorbol myristate acetate induced activation of MAP kinases. Pretreatment of adipocytes with the MAP kinase kinase inhibitor PD 98059 was without effect on the insulin-induced activation of PDE 3B. Furthermore, phorbol myristate acetate stimulation did not result in phosphorylation/activation of PDE 3B or activation of the kinase that phosphorylates PDE 3B. Using Mono Q and Superdex chromatography, the kinase that phosphorylates PDE 3B was found to co-elute with PKB, but not with p70 S6 kinase or MAP kinases. Furthermore, both PKB and the kinase that phosphorylates PDE 3B were found to translocate to membranes in response to peroxovanadate stimulation of adipocytes in a wortmannin-sensitive way. Whereas these results suggest that p70 S6 kinase and MAP kinases are not involved in the insulin-induced phosphorylation/activation of PDE 3B in rat adipocytes, they are consistent with PKB being the kinase that phosphorylates PDE 3B.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1997

Selection for spiral waves in the social amoebae Dictyostelium.

Starving Dictyostelium amoebae emit pulses of the chemoattractant cAMP that are relayed from cell to cell as circular and spiral waves. We have recently modeled spiral wave formation in Dictyostelium. Our model suggests that a secreted protein inhibitor of an extracellular cAMP phosphodiesterase selects for spirals. Herein we test the essential features of this prediction by comparing wave propagation in wild type and inhibitor mutants. We find that mutants rarely form spirals. The territory size of mutant strains is approximately 50 times smaller than wild type, and the mature fruiting bodies are smaller but otherwise normal. These results identify a mechanism for selecting one wave symmetry over another in an excitable system and suggest that the phosphodiesterase inhibitor may be under selection because it helps regulate territory size.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1997

Zinc dependent activation of cAMP-specific phosphodiesterase (PDE4A).

Cyclic nucleotide phosphodiesterases (PDE), including PDE4A, contain two consensus sequences (HX3HX24-26E) which have been associated with Zn2+ binding and activation with other proteins. This study shows that Zn2+ activates purified recombinant human PDE4A with an EC50 of <1 microM. The EC50 for Mg2+, the generally accepted activating metal ion, is approximately 100 microM. Zn2+ concentrations higher than 5 microM are inhibitory. Mn2+, Co2+ and Ni2+ also activate PDE4A with EC50 values of approximately 2, 3 and 10 microM, respectively. PDE4A binds 65Zn2+ with a Kd of 0.4 microM and approximately 1:1 stoichiometry. Titrations of PDE4A inhibition with Mg2+ and Zn2+ as activating metal ions showed that the competitive inhibitors R-Rolipram, CDP-840, RS-14203 and KF18280 are shifted at least 10-fold to lower potency in the presence of Zn2+. The effect is likely at the site of inhibitor binding as the Km for cAMP in the presence of Mg2+ and Zn2+ is similar (1-3 microM). The Kd of [3H]-R-Rolipram for PDE4A was increased at least 30-fold from 3 nM (with Mg2+) by the presence of Zn2+. The high affinity of Zn2+ for PDE4A indicates that this metal may play a role in the regulation of PDE4A activity.

3',5'-Cyclic-AMP Phosphodiesterases↗