[Mutually potentiating effect of joint action of carbacholine and histamine on secretion and the isoenzyme spectrum of pepsin from frog gastric mucosa cells]. / Vzaimopotentsiiruiushchii éffekt sovmestnogo deistviia karbakholina i gistamina na sekretsiiu i izofermentnyi spektr pepsina iz kletok slizistoi obolochki zheludka liagushki.

Pepsin secretion was studied in vivo in the primary culture of isolated secretory gastric mucosa cells of the frog (Rana ridibunda). The injection of animals with carbacholin (200 micrograms/100 g weight) or histamine (100 micrograms/100 g weight) or addition of the hormones (100 microM) into the incubation medium of isolated gastric cells significantly increased pepsin activity. In vitro, preliminary addition of the specific antagonists of these hormones to the incubation medium (1 microM atropine or 100 microM cimetidine) completely suppressed the effects of hormones. The effect of histamine is season-dependent. Combined injection or simultaneous addition to incubation medium of isolated cells of carbacholin and histamine caused mutual potentiation of their effects. In this case, the quantitative response of the cells exceeded the theoretical sum of the stimulatory effects of each of these two hormones alone. According to electrophoresis, the hormones cause quantitative changes in isozyme spectrum of proteolytic enzymes but do not significantly affect their qualitative characteristics.

[Participation of protein kinase C in hormonal regulation of pepsin secretion in the rat stomach]. / Uchastie proteinkinaszy C v gormonal'noi reguliatsii sekretsii pepsinav zheludke krys.

It was shown that pentagastrin (0.5 micrograms/100 g of body mass) increases the activity of Ca2+ and phospholipid-dependent protein kinase C in the membrane fraction of rat gastric mucosa cells. This effect of pentagastrin is accompanied by a decrease of the protein kinase C activity in the cytosolic fraction. Chromatography of the membrane fraction revealed an additional peak of the enzyme activity. Analysis of isolated gastric mucosa cells demonstrated that pentagastrin (10(-8)-10(-6) M) (but not 10(-4) M histamine) added to the incubation mixture increased the protein kinase C concentration in the membranes. The pentagastrin effect was directly correlated with the amount of pepsin-producing chief cells in the cellular pools. Carbacholine, another well-known pepsin secretion stimulator, was able to activate, similar to pentagastrin, the protein kinase C activity. It is concluded that protein kinase C plays a prominent role in hormonal regulation of the chief gastric cell function.

[Secondary messengers in the hormonal regulation of the functional activity of the main and mucoid cells in the stomach]. / Vtorichnye messendzhery v gormonal'noi reguliatsii funktsional'noi aktivnosti glavnykh i mukoidnykh kletok zheludka.

The messenger role of Ca+2, cyclic nucleotides and inositol triphosphates in the stimulation of pepsinogen and mucous secretion were studied using isolated pig [correction of nug] gastric chief cells and guinea pig mucous cells, resp. Pepsinogen secretion was stimulated by agents either working at the postreceptor adenylate cyclase (AC) level (db-cAMP, forskolin) or after 12-o-tetradecanoyl-phorbol-13-acetate (TPA) stimulation of protein kinase C (PK C). Similar secretory effects were observed with histamine (H), carbachol (C) and cholecystokinin (CCK). [Ca-2] in was elevated by C and by CCK, but not by H in both types of cells. Like TPA, both C and CCK, but not H, stimulated the Ca+2-sensitive particulate PK C. H increased the activity of cAMP-dependent PK A. PGE2, C and CCK were found to increase inositol-1,4,5-triphosphate content in mucous cells. The findings indicate that two pathways of the regulation of pepsinogen and mucous secretion (AC-cAMP-PK C and phosphoinositol breakdown cascade) can act synergistically.

Biochemical mechanisms of regulation of mucus secretion by prostaglandin E2 in rat gastric mucosa.

The effects of prostaglandin E2 (PGE2) and inhibitors of RNA and protein synthesis on rat gastric mucosa were investigated in order to study the cellular and biochemical mechanisms involved in the PGE2-stimulated formation and secretion of gastric mucus. It was shown that PGE2 caused significant stimulation of gastric mucus secretion and this effect of PGE2 was inhibited by cycloheximide but not actinomycin D. The influence of PGE2 on the in vitro incorporation of N-acetyl-[3H]glucosamine and 14C-labelled amino acids in to the glycoproteins representing a major mucus component of the isolated gastric mucosa cells was also studied. The stimulatory effect of PGE2 on incorporation of labelled precursors into glycoproteins of gastric cells was also inhibited by cycloheximide. These results suggest that the effect of PGE2 on mucus production requires ongoing protein synthesis. cAMP can fully reproduce the effect of PGE2 on the formation and the secretion of gastric mucus. The binding of [3H]PGE2 to rat gastric non-parietal cell fractions consisting predominantly of mucoid cells correlated with the ability of PGE2 to increase adenylate cyclase activity in these cells. PGE2 had no effect on adenylate cyclase activity in cell suspensions enriched in parietal cells. These data suggest further that the stimulatory effect of PGE2 on mucus secretion may be mediated by cAMP as a messenger.

[Quantitative analysis of the ultrastructure of gastric mucocytes in the rat after prostaglandin treatment]. / Kolichestvennyi analiz ul'trastruktury mukotsitov zheludka krys posle deistviia prostaglandina.

Effect of prostaglandin E2 (PGE2) on mucus secretion by mucocytes of the fundal part of the rat stomach has been studied electron microscopically, morphometrically and biochemically. PGE2 is found to stimulate synthesis of glycoproteins and their secretion by the mucocytes that results in increasing the relative volume of Golgi complex and in decreasing that of secretory granules. Actinomycin does not affect and cycloheximide blocks the stimulating activity of prostaglandin. This demonstrates that prostaglandin produces its action at the posttranscriptional (translational) level controlling mucus secretion of mucocytes. Owing to the results of the investigation and of those previously obtained on incorporation of 3H-pentagastrin and 3H-histamine into the cells of the mucous tunic, at least two mechanisms are supposed to control the gastric mucus secretion.

[Prostaglandin E2 binding by gastric mucosa cells in the rat]. / Sviazyvanie prostaglandina E2 kletkami slizistoi obolochki zheludka u krys.

After incubation of gastric pieces with [3H] prostaglandin E2 (PGE2) the label is accumulating predominantly over the cells situating in the middle third of the gastric glands proper, where mucus-secreting cells are mainly situated. As demonstrate biochemical experiments, [3H] PGE2 combines 5.5 times as intensively with the isolated cells fraction, which consists mainly of mucocytes but not of parietal cells. A suggestion is made that prostaglandin E2 contributes to biosynthesis and mucus secretion in the stomach when it immediately combines with mucocytes.

[Biochemical mechanisms of the regulation of gastric mucus secretion in the rat: the role of prostaglandin E2 and histamine]. / Biokhimicheskie mekhanizmy reguliatsii vydeleniia zheludochnoi slizi u krys: rol' prostaglandina E2 i gistamina.

Both prostaglandin E2 (PGE2) and histamine activated the adenylate cyclase system of rat gastric cells. Parietal acid-producing cells of the stomach were the target-cells for histamine, while PGE2 affected the mucous cells of gastric glands. The stimulating effect of PGE2 on mucus production occurred due to activation of protein synthesis. Electron microscopy of mucous cells detected alterations in structure of cells involved in biosynthesis of mucoids. Histamine appears to cause its effect on secretion of gastric mucus via the activating influence on production of hydrochloric acid.

[Effect of prostaglandin E2, cAMP and histamine on glycoprotein synthesis in isolated cells of the rat gastric mucosa]. / Vliianie prostaglandina E2, cAMP i gistamina na sintez glikoproteinov v izolirovannykh kletkakh slizistoi obolochki zheludka krys.

It was discovered that prostaglandin E2 (PGE2), but not histamine, increased the incorporation of 3H-N-acetyl-D-glucosamine and 14C-amino acids into the acid-insoluble protein fraction of isolated, mainly mucoid cells of rat gastric mucosa. The cAMP at the dose of 1 mM enhanced, like the PGE2, the synthesis of gastric mucoids. Cycloheximide inhibited the basal incorporation of labelled N-acetyl-D-glucosamine and the amino acid mixture by 28 and 72%, respectively, and blocked completely the PGE2 effect on glycoproteins formation. It is suggested that the PGE2, unlike histamine, enhances the biosynthesis of glycoproteins in the mucoid cells of rat gastric mucosa. The cAMP is believed to be a messenger of the PGE2 effect.

[Effect of pentagastrin, histamine, cyclic-3',5'-AMP and prostaglandin E2 on the secretion of mucus in the rat stomach]. / Vliianie pentagastrina, gistamina, tsiklicheskogo 31,51-AMF i prostaglandina E2 na sekretsiiu slizi v zheludke krys.

Pentagastrin as well as transmitters of its effect histamine and cAMP, affecting the HCl secretion, increased the gastric mucus secretion apparently due to stimulation of HCl production. This assumption is supported by experiments in which the histamine effect was not inhibited by cycloheximide but was completely eliminated in presence of burimamide--a drug blocking histamine H2-receptors. Prostaglandin E2 which inhibited distinctly basal secretion of HCl but did not affect the pepsin secretion, elevated markedly the mucus production. The effect of this stimulator of mucus production, which differed from histamine in its ability to inhibit HCl secretion, was mediated via the processes of translation but not of transcription. Regulation of mucus secretion in stomach, similarly to HCl and pepsin secretion, appears to involve a multicomponent cascade system, including prostaglandin E2 as one of transmitters. cascade system, including prostaglandin E2 as one of the transmitters.

[Localization of (3H)histamine and (3H)prostaglandin E2 receptors in isolated cells of rat gastric mucosa]. / Lokalizatsiia retseptorov [3H]gistamina i [3H]prostaglandina E2 v izolirovannykh kletkakh slizistoi zheludka krys.

Isolated cells of rat gastric mucosa were obtained by treatment of rat stomach with pronase. Two fractions were isolated, one of which was rich (up to 90%) and the second one poor (to 25%) of parietal cells. Using specific antagonists and agonists of H1- and H2-receptors of histamine (diphenhydramine, metiamide, cimetidine, impromidine, dimaprit) the H2-receptors of histamine were shown to be localized in parietal cells. A preferential binding of (3H)prostaglandin E2 by the receptor proteins of plasma membranes of non-parietal (presumably mucoid) cells was found. The data obtained indicate that rat gastric mucosa contains receptors of histamine and PGE2 which differ in their intracellular localization and strictly selectively bind (3H)histamine and (3H)PGE2. It is assumed that the starting point in the mechanism of action of these intercellular regulators on gastric secretion is probably the process of their specific recognition by the protein receptors localized in functionally different cells.

[Cellular localization of adenyl cyclase activated by histamine and prostaglandin E2 in rat gastric mucosa and their role in regulation of gastric secretion]. / Kletochnaia lokalizatsiia adenilattsiklaz, stimuliruemykh gistaminom i prostaglandinom E2, v slizistoi obolochke zheludka krys i ikh rol' v reguliatsii zheludochnoi sekretsii.

It was shown that cimetidine, the inhibitor of H2-receptors of histamine, does not affect the activation of adenylate cyclase by prostaglandin E2 (PGE2) in rat gastric mucosa homogenate. At the same time cimetidine completely inhibits the stimulating effect of histamine on the adenylate cyclase activity. Using isolated rat gastric cells separated into fractions rich (to 90%) and poor (up to 25%) of parietal cells, it was demonstrated that the prostaglandin-stimulated adenylate cyclase is localized in the non-parietal (presumably mucoid) cells, while the histamine-sensitive one is localized in parietal acid-producing cells. The mechanisms of histamine and PGE2 action are discussed and a scheme of participation of these substances in regulation of gastric secretion is proposed.