16,16-Dimethyl prostaglandin E2 suppresses the increases in the proliferative activity of rat colonic epithelium induced by indomethacin and aspirin

Treatment of rats with indomethacin rapidly increased ornithine decarboxylase (4 h) of colonic mucosa and [3H]thymidine incorporation into colonic mucosal deoxyribonucleic acid (DNA) (1 or 5 days) when this parameter was examined in vivo and ex vivo. The changes in colonic mucosal ornithine decarboxylase and DNA synthesis induced by indomethacin were correlated temporally with suppression of colonic prostaglandin synthesis, as assessed from ex vivo colonic production of prostaglandin E, the dominant prostaglandin product of colon. Autoradiographic studies indicated that the enhancement of proliferative activity of colonic epithelium after treatment with indomethacin for 1 day was confined to the lower third of the colonic crypt (normal proliferative zone). After 5 days of indomethacin treatment, however, there was an extension of the proliferative zone to the upper third of the colonic crypts. Concurrent treatment of rats with the stable prostaglandin E2 analogue, 16,16-dimethyl prostaglandin E2, suppressed indomethacin-induced increases in colonic mucosal ornithine decarboxylase and DNA synthesis. Concurrent administration of 16,16-dimethyl prostaglandin E2 also prevented the extension of the proliferative zone of colonic epithelium induced by 5 days of indomethacin administration. 16,16-Dimethyl prostaglandin E2 alone for 1-5 days had no detectable effects on colonic mucosal ornithine decarboxylase and DNA synthesis compared with corresponding control values. Increases in colonic mucosal DNA synthesis were also induced by treatment of rats for 5 days with aspirin (ASA). The stimulation of colonic mucosal DNA synthesis induced by ASA was significantly suppressed by concurrent administration of 16,16-dimethyl prostaglandin E2 and was also correlated with the inhibition of colonic prostaglandin synthesis by ASA. The colons of rats treated with indomethacin for 1 day or ASA for 5 days appeared normal by light microscopy. However, treatment of rats for 5 days with indomethacin resulted in mild to moderate inflammation of the lamina propria and some goblet cell depletion at the mucosal surface, but no loss of surface epithelium. The ultrastructure of the surface epithelium of the colons of rats treated with indomethacin or ASA was normal as assessed by electron microscopy. The results thus demonstrate that inhibition of local colonic prostaglandin synthesis is associated with increases in the proliferative activity of colonic epithelium, and that these increases are suppressed by administration of 16,16-dimethyl prostaglandin E2.(ABSTRACT TRUNCATED AT 400 WORDS)     

Sustained increase in the proliferation of rat colonic mucosa during chronic treatment with aspirin

The effects of indomethacin and aspirin on colonic epithelial proliferative activity, colonic prostaglandin synthesis, and colonic mucosal cyclic adenosine 3',5'-monophosphate content were examined. Administration of indomethacin (3 mg/kg.day, s.c.) for 2 wk suppressed ex vivo colonic prostaglandin E2 production by 50% and increased [3H]thymidine incorporation into mucosal DNA in vivo, but induced colonic inflammation. Higher doses of indomethacin were toxic and associated with high mortality. By contrast, administration of aspirin (50 mg/kg.day, s.c.) for 2-20 wk suppressed colonic prostaglandin E2 production by 97% and was unassociated with colonic inflammation or systemic toxicity. Suppression of colonic prostaglandin E2 production was associated with a sustained stimulation of [3H]thymidine incorporation into colonic mucosal deoxyribonucleic acid (2-20 wk) and an increase in the [3H]thymidine labeling index when examined at 20 wk. Basal cyclic adenosine 3',5'-monophosphate content of colonic mucosa was markedly reduced in aspirin-treated rats. Moreover, addition of dimethyl prostaglandin E2 or 8-Br-cyclic adenosine 3',5'-monophosphate suppressed the elevated levels of [3H]thymidine incorporation into mucosal deoxyribonucleic acid in incubated colonic segments from aspirin-treated rats. The results demonstrate that sustained suppression of colonic prostaglandin synthesis by aspirin is associated with a persistent increase in colonic epithelial proliferative activity. They support a role for local colonic prostaglandin synthesis as a negative modulator of epithelial growth, possibly mediated through increases in colonic mucosal cyclic adenosine 3',5'-monophosphate.     

Colonic azodisalicylate metabolism determined by in vivo dialysis in healthy volunteers and patients with ulcerative colitis

Azodisalicylate, a second generation drug of sulfasalazine, delivers twice the amount of 5-aminosalicylic acid to the colonic lumen on a molar basis when split by bacterial azoreductases. In 6 patients with inactive ulcerative colitis, the colonic metabolism of sulfasalazine and azodisalicylate was studied by equilibrium in vivo dialysis of feces to measure the therapeutically relevant concentrations of their metabolites (5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid) in free fecal water. After oral intake of sulfasalazine (2 g/day) the total luminal concentrations of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid determined by high-performance liquid chromatography were higher (median 14 mmol/L) than previously reported and almost doubled (median 25 mmol/L, p less than 0.05) when sulfasalazine was replaced by the same dose of azodisalicylate. In contrast, the corresponding serum concentrations were negligible. After administration of azodisalicylate to 12 healthy volunteers, a similar distribution of the metabolites was found. In nearly all cases, the concentrations of azodisalicylate in fecal dialysates were below the detection limit (6 mumol/L). We conclude, therefore, that oral azodisalicylate is a highly effective means of delivery of 5-aminosalicylic acid to the colonic mucosa. In addition, determination of the active metabolites in free fecal water seems important for the interpretation of results obtained in vitro concerning the mode of drug action.     

Role of activation of protein kinase C in the stimulation of colonic epithelial proliferation by unsaturated fatty acids

Some, but not all, studies have suggested that high-fat diets promote colon carcinogenesis, possibly by stimulating the proliferative activity of colonic epithelium. Both the increase in colonic excretion of bile salts and of fatty acids that occur with an increase in fat ingestion have been implicated as stimuli of epithelial proliferative activity. In this study, we examined the role of activation of protein kinase C in fatty acid-induced stimulation of colonic epithelial proliferation in the rat. Intracolonic instillation of arachidonate, linoleate, or oleate at concentrations that did not induce surface cell injury or loss increased colonic mucosal ornithine decarboxylase activity and stimulated incorporation of [3H]thymidine into mucosal deoxyribonucleic acid. The saturated fatty acid palmitate was without effect. Arachidonate, linoleate, and oleate each induced the translocation of protein kinase C activity from the soluble fraction to the membrane fraction of colonic mucosa, an index of enzyme activation. The translocation of protein kinase C induced by unsaturated fatty acids occurred both in vivo after intracolonic instillation of these agents and in vitro upon incubation of isolated colonic crypt epithelium with fatty acids. The effects of the unsaturated fatty acids on both enzyme translocation and colonic epithelial proliferative activity were suppressed by 1-(5-isoquinolinyl)-2-methylpiperazine, an inhibitor of protein kinase C activity. Unsaturated fatty acids directly stimulated soluble colonic mucosal protein kinase C activity when added to the enzyme assay mixture. This action was blocked by 1-(5-isoquinolinyl)-2-methylpiperazine. However, unsaturated fatty acids also increased the breakdown of polyphosphoinositides when added to isolated colonic epithelium. The increase in polyphosphoinositide breakdown resulted in release of diacylglycerol, an endogenous activator of protein kinase C. Thus, unsaturated fatty acids may activate protein kinase C of colonic epithelium through either a direct intracellular effect or through an action on the cell membrane. The results support a role for protein kinase C in the stimulation of colonic epithelial proliferation by unsaturated fatty acids.     

Effects of intraluminal epidermal growth factor on mucosal proliferation in the small intestine of adult rats

To determine whether intraluminal administration of epidermal growth factor (EGF) has a trophic effect on small bowel mucosa, catheters were surgically placed in the ileum of adult rats and infused with EGF. Comparing animals receiving EGF (5 micrograms/48 h) with controls, in the ileum mean mucosal ornithine decarboxylase specific activity increased by greater than 200% (p less than 0.001), mean deoxyribonucleic acid specific activity and crypt labeling index increased by greater than or equal to 100% (p less than 0.001), and mean deoxyribonucleic acid content of the mucosa increased by 25% (p less than 0.05). During these studies, the jejunum was not exposed to ileal infusate, as shown with the use of a phenol red marker. Nevertheless, all measurements except deoxyribonucleic acid content increased in the jejunum as well, although to a lesser extent. A greater rise in mucosal ornithine decarboxylase and deoxyribonucleic acid specific activity could be demonstrated in the jejunum when EGF was infused directly into this segment. Mucosal ornithine decarboxylase activity was found to be dose-dependent and to increase in the ileum only after a latent period of 12-24 h. We conclude that intraluminal administration of EGF stimulates a mucosal proliferative response in the small intestine. Intraluminal EGF appears likely to be one of a number of endogenous trophic factors in the small bowel.     

Sulfasalazine reduces bile acid induced apoptosis in human hepatoma cells and perfused rat livers

BACKGROUND: Bile acid induced apoptosis in hepatocytes can be antagonised by nuclear factor kappaB (NFkappaB) dependent survival pathways. Sulfasalazine modulates NFkappaB in different cell types. We aimed to determine the effects of sulfasalazine and its metabolites sulfapyridine and 5-aminosalicylic acid (5-ASA) on bile acid induced apoptosis in hepatocytes. METHODS: Apoptosis was determined by caspase assays and immunoblotting, NFkappaB activation by electrophoretic mobility shift assay and reporter gene assays, generation of reactive oxygen species (ROS) fluorometrically, bile secretion gravimetrically, and bile acid uptake radiochemically and by gas chromatography in HepG2-Ntcp cells and isolated perfused rat livers. RESULTS: Glycochenodeoxycholic acid (GCDCA 75 micromol/l) induced apoptosis was reduced by sulfasalazine dose dependently (1-1000 micromol/l) in HepG2-Ntcp cells whereas its metabolites 5-ASA and sulfapyridine had no effect. Sulfasalazine significantly reduced GCDCA induced activation of caspases 9 and 3. In addition, sulfasalazine activated NFkappaB and decreased GCDCA induced generation of ROS. Bile acid uptake was competitively inhibited by sulfasalazine. In perfused rat livers, GCDCA (25 micromol/l) induced liver injury and extensive hepatocyte apoptosis were significantly reduced by simultaneous administration of 100 micromol/l sulfasalazine: lactate dehydrogenase and glutamate-pyruvate transaminase activities were reduced by 82% and 87%, respectively, and apoptotic hepatocytes were observed only occasionally. GCDCA uptake was reduced by 45 (5)% when sulfasalazine was coadministered. However, when 50% of GCDCA (12.5 micromol/l) was administered alone, marked hepatocyte apoptosis and liver injury were again observed, questioning the impact of reduced GCDCA uptake for the antiapoptotic effect of sulfasalazine. CONCLUSION: Sulfasalazine is a potent inhibitor of GCDCA induced hepatocyte apoptosis in vitro and in the intact liver.     

Colonic N-acetylation of 5-aminosalicylic acid in inflammatory bowel disease

5-Aminosalicylic acid presently is believed to represent the therapeutically active moiety of the sulfasalazine molecule in the treatment of inflammatory bowel disease. The metabolism of this compound, however, has not been studied in detail. In this paper we provide evidence that 5-aminosalicylic acid is acetylated to N-acetyl-aminosalicylic acid in homogenates from colonic biopsy specimens (370 +/- 20 nmol/g wet wt or 2.9 +/- 0.9 nmol/mg.min, n = 10), whereas acetylation in fecal samples was only small (13.0 +/- 3.0 nmol/g). Mucosal N-acetylation was rapid, cofactor- and pH-dependent, and could be enriched in the cytosolic fraction. In contrast, fecal acetylation was slow and did not depend on the presence of acetyl-coenzyme A. There were neither significant differences of acetylation between patients and controls nor a significant correlation to the individual acetylation phenotype. From our results we believe that presystemic acetylation of 5-aminosalicylic acid may be mainly mediated by a colonic mucosal enzyme and only to a small extent by fecal (bacterial) processes.     

In vitro immunomodulatory effects of sulfasalazine and its metabolites

We assessed the in vitro effects of sulfasalazine and its 2 main metabolites, sulfapyridine (SP) and 5-aminosalicylic acid (5-ASA) on functional aspects of peripheral blood lymphocytes (PBM) of normal controls and patients with rheumatoid arthritis (RA). Sulfasalazine, but not its 2 main metabolites, inhibited mitogen induced proliferative responses of PMB at high drug concentrations (100 micrograms/ml). Similar results were obtained with purified B lymphocytes. Sulfasalazine depressed, in a dose dependent manner, pokeweed mitogen induced Ig synthesis by PBM of normals and patients with RA. Moreover, synthesis of IgM rheumatoid factor was depressed to a greater degree than total IgM at low sulfasalazine concentrations (10-25 micrograms/ml). Both SP and 5-ASA were not inhibitory at the concentrations tested. Experiments with purified lymphocyte subpopulations indicated that sulfasalazine exerted its major inhibitory activity on the B lymphocyte. These studies indicate that sulfasalazine, but not its 2 main metabolites, has immunomodulatory characteristics which may be related to its therapeutic activity in RA.     

Studies of two novel sulfasalazine analogs,ipsalazide and balsalazide

Sulfasalazine appears to exert its beneficial effect in colitis by releasing 5-aminosalicylic acid in the colon, but its use can be limited by side effects. Ipsalazide and balsalazide are novel sulfasalazine analogs designed to release 5-aminosalicylic acid and a nontoxic carrier molecule in the gastrointestinal tract. They have a low oral toxicity following single or repeat administration to mouse, rat, and ferret, and balsalazide is not mutagenic in the Ames test. Ipsalazide and balsalazide are split in rat and man, and the urinary and fecal excretion pattern of the 5-aminosalicylic acid released is similar to that of sulfasalazine; the carrier molecules are absorbed to a lesser extent than the sulfapyridine derived from sulfasalazine. These two analogs deserve therapeutic trial.     

Sulfasalazine-induced abnormal sperm penetration assay reversed on changing to 5-aminosalicylic acid enemas

Sulfasalazine, a drug used in the treatment of inflammatory bowel disease, has been associated with male infertility, an effect attributed to sulfapyridine rather than to 5-aminosalicylic acid (5-ASA), the presumed therapeutically active component of sulfasalazine. Recently, the sperm penetration assay (SPA) has been found to be an accurate method of quantitating male fertilization potential. We report the case of a man with ulcerative colitis in whom infertility and a markedly abnormal SPA were demonstrated while he was taking sulfasalazine. Shortly after discontinuing sulfasalazine and initiating treatment with 5-ASA enemas, his SPA became normal and his wife became pregnant. The SPA is a useful screening test for sulfasalazine-induced male infertility. On the other hand, 5-ASA enemas do not appear to be associated with an abnormal SPA.     

Sulfasalazine and 5-aminosalicylic acid inhibit contractile leukotriene formation

Sulfasalazine, used therapeutically in the treatment of ulcerative colitis, is cleaved in vivo to form 5-aminosalicylic acid (5-ASA) and sulfapyridine. In an isolated preparation of rat peritoneal cells both sulfasalazine (IC50 = 0.15 mM) and 5-ASA (IC50 = 2.3 mM), but not sulfapyridine, inhibited calcium ionophore-stimulated formation of contractile leukotriene activity. This activity, although not identified directly, is attributable to a mixture of leukotriene C4 and leukotriene D4 (commonly referred to as SRS-A, or slow-reacting substance of anaphylaxis). Reference compounds evinced expected activities (IC50 = 0.024 mM for phenidone, IC50 = 0.3 microM for nordihydroguaiaretic acid, IC50 = 0.033 mM for BW 755C), whereas para-aminosalicylic acid and thiosalicylic acid were inactive. These properties of sulfasalazine may contribute to its therapeutic efficacy in vivo.     

Modulation of human colonic lamina propria lymphocyte proliferation

Bile acids were been implicated in several pathologic processes, such as secretory diarrhea, carcinogenesis, and immunomodulation of human peripheral blood lymphocytes. Nevertheless, their effect on the human gut immune system is not known. In this study we investigate the effect of several bile acids (cholate, deoxycholate, chenodeoxycholate) and 13-hydroperoxylinoleic acid (conc. 0.1-1000, microM) on human colonic lamina propria lymphocyte (LPL) DNA synthesis and cell proliferation. In addition, the effect of these bile acids on LPL ornithine decarboxylase activity was also determined. Significant dose-dependent inhibition of [3H]thymidine incorporation in Con A-stimulated LPL was observed. Parallel inhibition was seen on LPL cell proliferation. Furthermore, bile acids inhibited ornithine decarboxylase activity in Con A-stimulated LPL. These effects on cell proliferation were not due to the LPL cytolysis as viability and cell membrane integrity were not altered. Our results suggest that bile acid has an immunoregulatory function on the human mucosal immune system and may have a role during pathological states.     

Modulation of mediator release from human intestinal mast cells by sulfasalazine and 5-aminosalicylic acid

Intestinal mast cells are thought to contribute to the mucosal inflammation in ulcerative colitis and Crohn's disease through release of inflammatory mediators. Since sulfasalazine and its metabolite 5-aminosalicylic acid are effective therapeutic agents in inflammatory bowel disease and have been shown to inhibit generation of inflammatory products in other cells, we examined the effect of these agentsin vitro on human intestinal mast cell mediator release. Sulfasalazine (5×10^{–4–10 –3} M) was found to significantly enhance goat anti-human IgE-induced histamine release from intestinal mast cells, which is the same response as seen in human blood basophils, whereas its metabolite 5-aminosalicylic acid was an effective inhibitor of stimulated histamine release in both mast cells and basophils. 5-Aminosalicylic acid also inhibited production of prostaglandin D₂ by the stimulated intestinal mast cells. Sulfasalazine alone, without immunologic stimulation, did not induce histamine release from mast cells or basophils, but the enhancement of ongoing mast cell activation by sulfasalazine may explain some cases of adverse reactions to the drug. The inhibition of mast cell histamine release and prostaglandin generation by 5-aminosalicylic acid demonstrates a potential therapeutic modality of this agent.This work was supported by the National Foundation for Ileitis and Colitis and the National Institute of Allergy and Infectious Disease grants AI07290 and AI08270.     

Modulation of human colonic arachidonic acid metabolism by sulfasalazine

The effects of sulfasalazine and its moieties on synthesis of individual products of arachidonic acid metabolism by human colonic mucosa have been investigated. Sulfasalazine inhibited synthesis of the lipoxygenase products. Sulfasalazine and sulfapyridine also inhibited synthesis of thromboxane B2 while enhancing synthesis of prostaglandin (PG) F2 alpha or PGE2, respectively. Inhibition of synthesis of lipoxygenase products and modulation of the profile of cyclooxygenase products could reduce inflammation and enhance mucosal resistance to damage in ulcerative colitis.     

5-Aminosalicylic acid protects against ischemia/reperfusion-induced gastric bleeding in the rat

The aim of the present study was to determine whether the split products of sulfasalazine, sulfapyridine, and 5-aminosalicylic acid can ameliorate ischemia/reperfusion-induced injury to the gastric mucosa. Gastric mucosal damage was assessed by measuring (a) 51Cr-labeled red blood cell leakage into the gastric lumen, (b) the area of gross mucosal lesions, and (c) the extent of histologically demonstrable mucosal damage. In rats treated with 5-aminosalicylic acid, but not in those treated with sulfapyridine, the leakage of 51Cr-labeled red blood cells and the area of gross mucosal lesions after ischemia/reperfusion were significantly reduced as compared with untreated (control) rats. Inasmuch as 5-aminosalicylic acid (the therapeutic moiety of sulfasalazine) has been reported to be a hydroxyl radical scavenger, we also assessed the effects of dimethylsulfoxide (another hydroxyl radical scavenger) on ischemia/reperfusion-induced gastric mucosal injury. In rats treated with dimethylsulfoxide, leakage of 51Cr-labeled red blood cells and the area of gross mucosal lesions after ischemia/reperfusion were significantly reduced as compared with control rats. The results of this study support the contention that ischemia/reperfusion-induced gastric bleeding involves the hydroxyl radical and indicate that 5-aminosalicylic acid significantly attenuates this vascular injury.     

Suppression of NF-kappaB activity by sulfasalazine is mediated by direct inhibition of IkappaB kinases alpha and beta

BACKGROUND & AIMS: Activation of NF-kappaB/Rel has been implicated in the pathogenesis of inflammatory bowel disease (IBD). Various drugs used in the treatment of IBD, such as glucocorticoids, 5-aminosalicylic acid, and sulfasalazine, interfere with NF-kappaB/Rel signaling. The aim of this study was to define the molecular mechanism by which sulfasalazine inhibits NF-kappaB activation. METHODS: The effects of sulfasalazine and its moieties on NF-kappaB signaling were evaluated using electromobility shift, transfection, and immune complex kinase assays. The direct effect of sulfasalazine on IkappaB kinase (IKK) activity was investigated using purified recombinant IKK-alpha and -beta proteins. RESULTS: NF-kappaB/Rel activity induced by tumor necrosis factor alpha, 12-O-tetradecanoylphorbol-13-acetate, or overexpression of NF-kappaB-inducing kinase, IKK-alpha, IKK-beta, or constitutively active IKK-alpha and IKK-beta mutants was inhibited dose dependently by sulfasalazine. Sulfasalazine inhibited tumor necrosis factor alpha-induced activation of endogenous IKK in Jurkat T cells and SW620 colon cells, as well as the catalytic activity of purified IKK-alpha and IKK-beta in vitro. In contrast, the moieties of sulfasalazine, 5-aminosalicylic acid, and sulfapyridine or 4-aminosalicylic acid had no effect. Activation of extracellular signal-related kinase (ERK) 1 and 2, c-Jun-N-terminal kinase (JNK) 1, and p38 was unaffected by sulfasalazine. The decrease in substrate phosphorylation by IKK-alpha and -beta is associated with a decrease in autophosphorylation of IKKs and can be antagonized by excess adenosine triphosphate. CONCLUSIONS: These data identify sulfasalazine as a direct inhibitor of IKK-alpha and -beta by antagonizing adenosine triphosphate binding. The suppression of NF-kappaB activation by inhibition of the IKKs contributes to the well-known anti-inflammatory and immunosuppressive effects of sulfasalazine.     

Measurement of colonic mucosal concentrations of 5-aminosalicylic acid is useful for estimating its therapeutic efficacy in distal ulcerative colitis: comparison of orally administered mesalamine and sulfasalazine

OBJECTIVES: Oral 5-aminosalicylic acid (5-ASA) preparations have been used frequently in the treatment of ulcerative colitis. However, there have been few reports investigating the relationship between colonic mucosal concentrations of 5-ASA and its clinical efficacy when oral sulfasalazine or 5-ASA compounds were administered. The aim of this study is to compare the mucosal concentrations of 5-ASA ensured by sulfasalazine or mesalamine, and to define the clinical significance of the measurement of 5-ASA concentrations in the treatment of distal ulcerative colitis. MATERIALS AND METHODS: Biopsies were taken from the rectum and sigmoid colon of the oral sulfasalazine group (n = 13) and the slow-release 5-ASA (mesalamine) group with (n = 5) or without (n = 11) rectal administration of 5-ASA. High-pressure liquid chromatography was used to measure the tissue concentrations of 5-ASA and its metabolites. We compared the 5-ASA concentrations of the sulfasalazine group with the mesalamine group. Furthermore, we analyzed the relationship between tissue 5-ASA concentrations and the Disease Activity Index (DAI). RESULTS: The concentrations of 5-ASA and acetyl-5-ASA in the sulfasalazine group were higher than those in the group taking oral mesalamine alone (p < 0.01). The concentration of 5-ASA was much higher in the patients who received oral and rectal mesalamine in an enema than in the patients who had oral mesalamine alone. There was a significant inverse correlation between the DAI and concentrations of 5-ASA in the rectum (r = 0.712, p < 0.001). CONCLUSIONS: We demonstrated that the colonic mucosal concentration of 5-ASA was significantly higher in the sulfasalazine group than in the mesalamine group. Furthermore, the concentrations of mucosal 5-ASA may be a good marker for the estimation of its efficacy in the treatment of ulcerative colitis.     

Sulfasalazine treatment and lymphocyte function in patients with rheumatoid arthritis

Sulfasalazine is now an established 2nd line agent in the treatment of rheumatoid arthritis (RA) but its mode of action is unknown. Two separate studies have investigated the possibility that it works in RA by influencing lymphocyte function. After 12 weeks of treatment with sulfasalazine, elevated levels of circulating activated lymphocytes and abnormal ex vivo mitogen response to concanavalin A (Con-A) in 11 patients with RA reverted to normal. An in vitro study investigated the effect of sulfasalazine and its metabolites on mitogen response by healthy and RA peripheral blood mononuclear cells (PBMC). Sulfapyridine (SP) and 5-hydroxy SP suppressed the response of RA PBMC to Con-A. Sulfasalazine, SP and N-acetyl SP suppressed the response of healthy PBMC to pokeweed mitogen. 5-aminosalicylic acid also affected mitogen response and cell viability, which may be relevant to actions of this metabolite within the gut.     

Postprandial stimulation of epithelial cell proliferation in defunctioned colon of rats is not caused by gastrin

Rats were submitted, at random, to either a diverting colostomy alone or to antrectomy with a colostomy. After a 48-h fasting period, animals from each group were refed, whereas control animals were kept fasting. Animals were killed at 0, 6, 12, 18, and 24 h after the time of refeeding. In vitro labeling of colon mucosa with [3H]thymidine and autoradiography were performed to determine the proliferative parameters in the colonic crypts, and scintillation counts on mucosal scrapings were used for the estimation of mucosal deoxyribonucleic acid synthetic activity. Refeeding increased the labeling index (p less than 0.01), mitotic index (p less than 0.01), and mucosal deoxyribonucleic acid synthesis activity (p less than 0.01) in the proximal colon as well as in the defunctioned distal segment. Despite suppression of the postprandial rise in serum gastrin (p less than 0.01), antrectomy did not abolish the proliferative reaction in any colonic segment. These data confirm the existence of a potent stimulant of colonic cell proliferation that is released systematically after feeding. They indicate that gastrin is not the responsible stimulant and that another, yet unknown, physiological factor is involved.     

Azodisalicylate (azodisal sodium) causes intestinal secretion. Comparative study of the effect of azodisalicylate, sulfasalazine, 5-aminosalicylic acid and sulfapyridine on the water and electrolyte transfer and the morphology of the rat ileum and colon in vivo

Azodisalicylate (ADS) is one of the possible successors of sulfasalazine in the treatment of ulcerative colitis. The following results were obtained when comparing the influence of ADS on net water and electrolyte transfer in tied-off loops of the rat ileum and colon in vivo with sulfsalazine, 5-aminosalicylic acid, and sulfapyridine. (1) Sulfasalazine, 5-aminosalicylic acid and sulfapyridine had no effect on water and electrolyte transfer of the healthy intestinal mucosa in concentrations up to 400 mg%. (2) ADS showed a concentration-dependent inhibition effect on net water, sodium and chloride absorption and stimulated secretion at concentrations higher than 100 mg%. (3) No morphological alterations of the mucosa could be observed by light and transmission electron microscopy. The observed effect of ADS might have some clinical significance in patients with a decreased absorptive capacity of the colon in ulcerative colitis, in contrast to healthy volunteers, where the high absorptive capacity of the colon might compensate the decreased absorption or stimulated secretion in the small intestine.