Purification and characterization of the antisecretory factor: a protein in the central nervous system and in the gut which inhibits intestinal hypersecretion induced by cholera toxin

The antisecretory factors (ASF) are hormone-like proteins which inhibit cholera toxin-induced intestinal hypersecretion. Although ASF concentrations in young control rats were low, those in old control rats and toxin-treated rats were high. Toxin-treated rats had 200 ED50 units/g wet weight of ASF in the pituitary gland, while their intestinal mucosa, bile and milk contained 3, 0.5 and 0.5 units/g. In adult man and in 8-9-month-old pig the pituitary level was about 20 units/g. The isoelectric points of ASF from pig and rat were 4.8 and 5.0, respectively, while the molecular size as determined by gel filtration on Bio-Gel P-150 was the same in both cases (Kav 0.43). The molecular weight as determined by SDS-polyacrylamide gel electrophoresis was 60,000 for ASF from porcine pituitary gland. One ED50 unit of the purified porcine ASF corresponded to about 10(-13) mol (1-5 ng) of protein. There were two different ASF from human pituitary gland: pI 5.2, Kav 0.43; and pI 4.5, Kav 0.6. Since antibodies against porcine ASF failed to neutralize the latter protein, it may be unrelated to porcine ASF; the human pI 5.2-protein and rat ASF were both neutralized, but less effectively than was porcine ASF. All the ASF molecules attached to agarose gel, from which they dissociated again in methyl alpha-D-glucose: porcine and rat ASF were eluted at 0.3-0.9 M methyl alpha-D-glucose, human pI 5.2-ASF at 0.1-0.9 M, and human pI 4.5-ASF at 0.1-1.5 M methyl alpha-D-glucose.     

Galanin: evidence for a hypothalamic site of action to release growth hormone

Galanin is a 29 amino acid peptide that was isolated and characterized from porcine intestinal extracts. The presence of galanin-like immunoreactivity in neuronal elements in the hypothalamus and median eminence suggested a role for it in the hypothalamic control of anterior pituitary function. A hypothalamic site of action of galanin to stimulate growth hormone (GH) release is suggested by our observation that doses as low as 50 picomoles when infused into the third cerebroventricle of conscious, unrestrained ovariectomized rats resulted in significantly elevated plasma levels of GH. This effect was specific for GH and was dose-related. The failure of galanin to alter GH release from dispersed, cultured anterior pituitary cells in vitro further suggests that endogenous galanin plays a neuromodulatory role at the level of the median eminence, possibly affecting the release of known GH-releasing and/or inhibiting factors.     

Molecular cloning and physical mapping of the hyd gene of Escherichia coli K-12

Abstract Passive transfer between rates of protection against cholera toxin (CT) was studied. Extracts of various organs, obtained from CT-immunized rats, were injected intravenously into non-immunized recipient rats. The ability of the extracts to inhibit CT-induced secretion in ligated jejunal loop were tested. A significant inhibition of the response to CT was achieved by extracts from hypophysis, brain and jejunal mucosa. Extracts from pancreas, spleen or adrenal glands were without effect, as were all extracts obtained from control rats. The antisecretory effects of the hypophysis extracts became intensified with increasing numbers of immunizations, and the antisecretory effect was most pronounced when the extract was injected immediately before the CT challenge. The active component of the hypophysis extract was heat-labile and negatively charged, suggesting an acidic protein as the mediator of the protective effect against CT.     

Effects of microinjection of various prostaglandins into the 3rd ventricle, median eminence and pituitary on plasma LH in rats.

The effects of microinjection of PG'S (PGE1, E2, F2a) into the 3rd ventricle, median eminence (ME) and anterior pituitary on plasma LH in rats were investigated. Blood samples were obtained by jugular puncture before, and 10 and 45 min after the injection of PGS (50 or 100 mug), plasma LH was measured by radioimmunoassay. In the 3rd ventricle microinjection, PGE2 prodiced a significant rise in plasma LH. PGE1 and F2a did not significantly after plasma LH levels. In the median eminence, PGE2 and E1 produced a significant rise in plasma LH. PGF2a did not alter plasma LH levels. In the pituitary, PGE2 and E1 produced a significant rise in plasma LH. PGF2a did not alter plasma LH levels. These observations indicate that PGs act directly on the hypothalamic-pituitary axis, and that particular PG may be involved in the release of particular horomones from the hypothalamus and pituitary.     

Prostaglandin E prevents indomethacin-induced gastric and intestinal damage through different EP receptor subtypes

Gastrointestinal ulcerogenic effect of indomethacin is causally related with an endogenous prostaglandin (PG) deficiency, yet the detailed mechanism remains unknown. We examined the effect of various PGE analogues specific to EP receptor subtypes on these lesions in rats and mice, and investigated which EP receptor subtype is involved in the protective action of PGE(2). Fasted or non-fasted animals were given indomethacin s.c. at 35 mg/kg for induction of gastric lesions or 10-30 mg/kg for intestinal lesions, and they were killed 4 or 24 h later, respectively. Various EP agonists were given i.v. 10 min before indomethacin. Indomethacin caused hemorrhagic lesions in both the stomach and intestine. Prior administration of 16,16-dimethyl PGE(2) (dmPGE(2)) prevented the development of damage in both tissues, and the effect in the stomach was mimicked by 17-phenyl PGE2 (EP1), while that in the small intestine was reproduced by ONO-NT-012 (EP3) and ONO-AE-329 (EP4). Butaprost (EP2) did not have any effect on either gastric or intestinal lesions induced by indomethacin. Similar to the findings in rats, indomethacin caused gastric and intestinal lesions in both wild-type and knockout mice lacking EP1 or EP3 receptors. However, the protective action of dmPGE(2) in the stomach was observed in wild-type and EP3 receptor knockout mice but not in mice lacking EP1 receptors, while that in the intestine was observed in EP1 knockout as well as wild-type mice but not in the animals lacking EP3 receptors. These results suggest that indomethacin produced damage in the stomach and intestine in a PGE(2)-sensitive manner, and exogenous PGE(2) prevents gastric and intestinal ulcerogenic response to indomethacin through different EP receptor subtypes; the protection in the stomach is mediated by EP1 receptors, while that in the intestine mediated by EP3/EP4 receptors.     

Failure of neurotransmitter blockers to alter PGE2-induced LH release.

The purpose of this study is to ascertain whether or not prostaglandin (PG) E2 induces LH release by modifying or mudulating the release or action of neural transmitters. PGE2 injected inv into spayed rats primed two days earlier with 10 mug estradiol benzoate increased the plasma levels of LH 10 min later as measured by radio-immunoassay. The peak of plasma LH was not changed by prior treatment with beta- or alpha-adrenergic receptor blockers, propranolol or phenoxybenzamine. The peak level of plasma LH did not alter in rats treated with DL-alpha-methyl-ptyrosine methyl ester HC1 (alpha-MPT) or sodium diethyldithiocarbamate (DDC). Similarly, the peak of plasma LH was not changed by prior treatment with imipramine. Adminisration of PGE2 produced an increase in anterior pituitary and plasma, but not hypothalamic cyclic AMP concomitantly with the elevation in plasma LH. Although it is possible that the effect of PGE2 could be mediated by another transmitter system, as yet unknown, or that the effect of PGE2 on LH release could be mediated via the adenylate cyclase-cyclic AMP system, the results indicate that PGE2 does not act trans-synaptically, but probably acts directly on LH-RH neurons.     

Human pituitary tumor-transforming gene (PTTG1) motif suppresses prolactin expression

Pituitary tumor-transforming gene (PTTG) originally isolated from GH-secreting pituitary adenoma cells causes in vitro cell transformation, in vivo tumorigenesis, and induces basic fibroblast growth factor. These functions require an intact C-terminal proline-proline-serine-proline motif. PTTG1 is abundantly expressed in human pituitary tumors and plays a role in the early stages of experimental prolactinoma formation. We now determined direct effects of PTTG1 on hormonal phenotypes of functional pituitary tumor cells. Overexpression of PTTG1 C terminus (amino acids 147-202) containing intact proline-proline-serine-proline motifs in rat prolactin (PRL)- and GH-secreting GH3 cells markedly abrogates PRL mRNA expression by more than 90% (P < 0.001) and hormone levels (P < 0.001) and PRL promoter activity (P < 0.01) compared with control vector cells or to a PTTG1 C terminus mutant (P163A, S165Q, P166L, P170L, P172A, and P173L). Wild-type PTTG1 C-terminal transfectants formed smaller (P < 0.05) sc tumors in rats compared with control or mutated PTTG1 C-terminal transfectants. Estrogen (10 nm) treatment for 48 h partially restored PRL expression in stable wild-type PTTG1 C-terminal transfectants. These results indicate that targeting PTTG1-mediated signaling alters the hormonal phenotype in pituitary cells and disrupted PTTG1 action may be a potential subcellular therapeutic tool for repressing PRL hypersecretion.     

Effect of hypertonic saline on the corticotropin-releasing hormone and arginine vasopressin content of the rat pituitary neurointermediate lobe

The changes in the levels of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) in the neurointermediate lobe of the pituitary (NIL) following hypertonic saline administration were examined in rats. The plasma osmotic pressure in rats receiving 2% NaCl for 8 days was greatly increased. Plasma AVP concentration in rats receiving 2% NaCl for 8 days were significantly higher than in control rats (566% of the control level). Plasma corticosterone was significantly higher in the saline-treated rats than in controls, whereas plasma ACTH was not significantly different. The pituitary ACTH concentration was much higher in the saline-treated rats than in controls. CRH in the NIL was increased significantly by saline treatment (419% of the control concentration), whereas the CRH in the paraventricular nucleus and median eminence of control and saline-treated rats did not differ significantly. The AVP in the NIL fell greatly in saline treated rats. The extract from both control and saline-treated rats showed a major peak for immunoreactive CRH, with a retention time identical to that of rat CRH. However, the peak was much higher in the extract from saline-treated rats. The immunoreactive AVP peak was greatly reduced in saline-treated rats. These results suggest that hypertonic saline administration increases the CRH in the NIL and causes AVP hypersecretion and/or hyperfunction of magnocellular-NIL CRH might be responsible for pituitary-adrenal stimulation in saline-treated rats.     

Effect of prostaglandin E2 on the small intestine of indomethacin-treated rats

In the present study, the protective effect of PGE2 on intestinal damage in indomethacin-treated adult rats was investigated. Ileal integrity was evaluated making use of different biochemical and histological parameters: activities of sucrase, maltase and diamine oxidase; concentrations of DNA, putrescine, spermidine and spermine; incorporation of 3H-thymidine into DNA; mitotic index and mucosal thickness. Results expressed per g of mucosal weight, showed that: maltase and diamine oxidase activities as well as DNA, spermidine and spermine concentrations decreased markedly in indomethacin-treated rats when compared to control rats; the decrease of maltase activity as well as DNA, spermidine and spermine concentration was less pronounced in PGE2-treated rats when compared to indomethacin-treated rats; 3H-thymidine incorporation into DNA and mitotic index values showed no significant variation in the course of different treatments; mucosal thickness increased strongly, in PGE2-protected rats. We suggest that PGE2 could protect the rat's intestinal mucosa against the effects of indomethacin through a trophic action on intestinal villi.     

Effect of chronic alcohol consumption on rat uterine spontaneous motility, prostaglandin production and triglyceride metabolism

The spontaneous isometric developed tension (IDT), the synthesis and release of prostaglandins (PGs) into the incubating medium and the metabolism of triglycerides (TGs) in uterine strips isolated from controls and chronic ethanol fed rats, were studied. In order to observe how the uterus of rats fed alcohol reacts during a situation of metabolic emergency, the above mentioned studies were done in the presence or in the absence of glucose in the incubating medium. The decrement of IDT as time progressed was significantly greater in strips obtained from rats which had been drinking 20% ETOH than in controls. Nevertheless, the absolute magnitude of the initial IDT was similar in both groups. On the other hand, the decline of the frequency of contractions (FC) of uterine strips isolated from controls and from ETOH-exposed rats, after 60 min of spontaneous activity was similar. When the uterine strips isolated from ETOH-exposed and from control rats were suspended in glucose-free solution they exhibited the same decrement of IDT and FC after 60 min of activity. The basal release of PGE1 and PGE2 was similar in control tissues incubated in medium containing glucose, but the output of PGE2 was significantly smaller than that of PGE1 in uterine strips isolated from ETOH-exposed rats. The production of PGE1 and PGE2 by uteri suspended in glucose-free medium was similar in control preparations. On the contrary the release of both PGs differs in uterine strips from ETOH-exposed rats, i.e. the output of PGE2 was significantly smaller than in controls and the release of PGE1 increased around 4-fold in comparison with controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antisecretory factor modulates GABAergic transmission in the rat hippocampus

Antisecretory Factor (AF) is a protein that has been implicated in the suppression of intestinal hypersecretion and inflammation. Intestinal secretion and inflammation are partly under local and central neural control raising the possibility that AF might exert its action by modulating neural signaling. In the present study we have investigated whether AF can modulate central synaptic transmission. Evoked glutamatergic and GABAergic synaptic transmissions were investigated using extracellular recordings in the CA1 region of hippocampal slices from adult rats. AF (0.5 microg/ml) suppressed GABA(A)-mediated synaptic transmission by about 40% while having no effect on glutamatergic transmission. Per oral administration of cholera toxin as well as feeding of rats with a diet containing hydrothermally processed cereals, known to upregulate endogenous AF plasma activity, mimicked the effect of exogenously administered AF on hippocampal GABAergic transmission. Our results identify AF as a neuromodulator and further raise the possibility that the hippocampus and AF are involved in a gut-brain loop controlling intestinal secretion and inflammation.     

The antisecretory factor: synthesis and intracellular localisation in porcine tissues

The antisecretory factor, AF, is a 41-kDa protein, cloned and sequenced from a human pituitary library. AF is a potent inhibitor of experimental intestinal hypersecretion in rats and pigs. An antiserum against the C-terminal of the truncated, recombinantly produced AF protein was raised in rabbits. The affinity-purified antiserum was used to study the expression of AF in mucosal membranes and in the pituitary gland of the pig; distinctly stained cells were found in lymphoid cells in the connective tissue of all parts of the gastrointestinal, respiratory and urinary tracts. Cytoplasmic AF was demonstrated in endocrine and epithelial cells in the pituitary gland. In situ hybridisation with a digoxigenin-labelled mRNA probe also demonstrated specific cytoplasmic staining in epithelial and lymphoid cells in all of these tissues. The cells stained by either method were similarly distributed topographically within the tissues. The results suggest that a specific defined cell population in these various tissues possesses the capability of both synthesising and storing the AF protein within the cellular cytoplasmic compartment.     

Effect of synthetic LH-RH and hypothalamic extracts on RNA synthesis by rat pituitaries in vitro (author's transl)]

Incorporation of 14C-Uridine in pituitary RNA from adults or prepuberal female rats in vitro, incubated with synthetic LH-RH or hypothalamic extracts, was studied in this work. RNA synthesis was not increased by any of the assayed stimuli in adult female rat pituitaries. The 14C-Uridine incorporation in pituitary prepuberal female rats increased in presence of synthetic LH-RH or adult female hypothalamic extracts, but not in presence of prepuberal female hypothalamic extracts. The differences found in the in vitro behaviour between pituitaries from prepuberal and adult female rats, and between their respective hypothalamic extracts, are attributables to the evolution of these organs along the sexual maturing process.     

Activation and inactivation of cyclo-oxygenase in rat alveolar macrophages by aqueous cigarette tar extracts.

Cyclo-oxygenase (COX) activity and its level of expression, the release of arachidonic acid (AA), and the accumulation of prostaglandins (PGs) were determined in isolated rat pulmonary alveolar macrophages (PAM) exposed to aqueous cigarette tar (ACT) extracts. COX activity increased 3-fold above the initial activity within 2 h of incubation with ACT extracts and gradually decreased below the initial activity after 8 h of incubation. The increased COX activity after 2 h of incubation did not lead to increased accumulation of PGE2. Accumulated levels of PGE2 increased dramatically after 12 h of incubation despite decreased COX activity in cells incubated with ACT extracts. This increased accumulation of PGE2 was greater in cells derived from vitamin E deficient rats compared with control rats. Release of AA from cells was dramatically increased in cells incubated with ACT extracts in parallel to PG accumulation. Thus increased accumulation of PGE2 despite decreased COX activity after 12 h of incubation is likely the result of increased substrate availability. These results suggest that, contrary to earlier reports, cigarette smoke stimulates the formation of PGs in alveolar macrophages. Increased PG production may lead to suppressed immune response and enhanced risk of tumorigenesis in smokers' lungs.     

Effects of prostaglandin E2 and D2 on the release of vasopressin and oxytocin

The effects of prostaglandin (PG) E2 and D2 on the plasma levels of arginine-vasopressin (AVP) and oxytocin (OXT) in rabbits, and on the release of the both hormones from the isolated posterior pituitary of rats were examined. An intraventricular administration of PGE2 to a rabbit raised the plasma levels of the both hormones. An intraventricular injection of PGD2 also increased the plasma level of OXT but not that of AVP. The release of AVP and OXT from fragments of the posterior pituitary of a rat was not influenced by perfusion with Eagle MEM medium containing 10(-6) or 10(-5) M PGE2 and D2.     

Prostaglandin E production by uteri of ovariectomized pregnant rats receiving antiprogesterone steroid or in which progesterone has been withdrawn.

Antiprogesterone steroid, ZK98299 (Schering, Germany) or RU38486 (Roussel Uclaf, France), has been administered to ovariectomized early pregnant rats receiving continuous steroid replacement. At 24 h later, uterine explants of rats treated with ZK98299 produced significantly greater amounts of prostaglandin E (PGE) than did controls or animals treated with RU38486. The PGE/PGF2 alpha production ratio for uteri of rats treated with ZK98299 or RU38486 was markedly lowered compared to controls, and a significant decrease occurred in the PGE/6-keto PGF1 alpha production ratio for rats treated with RU38486. For ovariectomized early pregnant rats in which progesterone has been withdrawn, a significant reduction in uterine PGE production occurred when compared to control animals. There was also a marked decrease in PGE/PGF2 alpha production ratio, and the PGE/6-keto PGF1 alpha production ratio tended to be lowered relative to controls. The stimulated production (as by ZK98299) or unchanged production of PGE (as by RU38486) indicates a selective action on uterine PGE synthesis among the antiprogesterone steroids, and these findings cannot be explained simply in terms of a blockage of progesterone receptors.     

Failure of neurotransmitter blockers to alter PGE2-induced LH release.

The purpose of this study is to ascertain whether or not prostaglandin (PG) E2 induces LH release by modifying or modulating the release or action of neural transmitters. PGE2 injected iv into spayed rats primed two days earlier with 10 microgram estradiol benzoate increased the plasma levels of LH 10 min later as measured by radioimmunoassay. The peak of plasma LH was not changed by prior treatment with beta- or alpha-adrenergic receptor blockers, propranolol or phenoxybenzamine. The peak level of plasma LH did not alter in rats treated with DL-alpha-methyl-p-tyrosine methyl ester HCl (alpha-MPT) or sodium diethyldithiocarbamate (DDC). Similarly, the peak of plasma LH was not changed by prior treatment with imipramine. Administration of PGE2 produced an increase in anterior pituitary and plasma, but not hypothalamic cyclic AMP concomitantly with the elevation in plasma LH. Although it is possible that the effect of PGE2 could be mediated by another transmitter system, as yet unknown, or that the effect of PGE2 on LH release could be mediated via the adenylate cyclase-cyclic AMP system, the results indicate that PGE2 does not act trans-synaptically, but probably acts directly on LH-RH neurons.     

Effects of lysine clonixinate on cyclooxygenase I and II in rat lung and stomach preparations

Lysine clonixinate (LC) is a drug of antiinflammatory antipyretic and analgesic activity that produces minor digestive side-effects. This fact induced us to think that LC is possibly a weak COX-1 inhibitor. In order to investigate our hypothesis we inhibited cyclooxygenase activity with LC or indomethacin (INDO) in rat lung and stomach obtained from rats treated with lipopolysacharide (LPS) and control rats. Rat lung preparations incubated with 14C-arachidonic acid synthesise mainly PGE2. LC at 2.5 and 4.1 x 10(-5) M does not modify the basal production of PGE2 (probably COX-1) but at 6.8 x 10(-5) M significantly inhibited PGE2 production (approximately 48.5% inhibition, P<0.001). On the other hand, INDO at 10(-6) inhibited the basal production of PGE2 by around 73%. In LPS-treated rats, the production of PGE2 was significantly higher than in the lungs of control rats, probably due to the induction of COX-2. The addition of LC at 2.7 and 4.1 x 10(-5) M recovered the control values of PGE2 inhibiting, probably only from COX-2 activity. LC at higher concentrations (6.8 x 10(-5) M) and INDO 10(-6) M inhibited PGE2 formed by COX-2 and also partly by COX-1 activity.