Biological and clinical associations of c-jun activation in human breast cancer

Sub-units and regulators of the activating protein-1(AP-1) complex have been implicated in breast-cancer biology, therapeutic response and prognosis. This study has immunocytochemically examined the impact of c-jun-protein activation on biological and clinical parameters in human primary breast cancers, employing an antibody specific for the serine 63-phosphorylated c-jun protein. Substantial nuclear immunostaining was commonly apparent, indicative of an activated c-jun pool, with associations with MAP-kinase-signalling elements, e.g., transforming growth factor-alpha (p = 0.04), epidermal growth factor receptor (p = 0.08), phosphorylated erk 1/2 MAP kinase (p = 0.001) and phosphorylated jun kinase (p = 0.05) Little association was noted with c-fos protein, perhaps indicating alternative AP-1 partners for c-jun with a diversity of cellular end-points. This may explain the lack of relationship with proliferation and grade, the imperfect association between increased c-jun activation and poorer survival (p = 0.061), and the apparent relationship with distant metastasis (p = 0.05). While increased c-jun activation related to poorer quality (p = 0.09) and shortened duration of endocrine response in oestrogen-receptor-positive patients (p = 0.018), no generalized effects on oestrogen-regulated gene products were noted, indicating that AP-1 influences on oestrogen-receptor/oestrogen-response element transactivation are unlikely to explain endocrine insensitivity. These data reinforce our belief that elevated AP-1 signalling influences aspects of the breast-cancer phenotype.

A possible divergent role for the oestrogen receptor alpha and beta subtypes in clinical breast cancer

We have examined the relative levels of oestrogen receptor beta (ERbeta) mRNA in 94 breast cancer specimens using a semi-quantitative RT-PCR procedure. We correlated its expression with ERalpha and various clinical, pathological and biochemical features of the disease. The level of ERbeta mRNA expression in these samples was found to be much lower than ERalpha. Although ERalpha mRNA species were found to be most frequently associated with histological grade I and II tumours, displaying tubular differentiation, low grades of nuclear pleomorphism and low mitotic activity, such features were not characteristic of ERbeta positive samples. Indeed, application of the Spearman rank correlation test revealed that there was an inverse association between ERbeta normalised levels and ERalpha protein HScore. Also ERbeta mRNA positive cancers were more frequently EGFR protein positive than their negative counterparts (p = 0.016), a feature normally associated with endocrine-insensitive disease. Our data suggest that although ERbeta levels are most likely lower than ERalpha, they may influence the biological behaviour of breast cancers containing low levels of ERalpha.

Gamma linolenic acid with tamoxifen as primary therapy in breast cancer

Gamma linolenic acid (GLA) has been proposed as a valuable new cancer therapy having selective anti-tumour properties with negligible systemic toxicity. Proposed mechanisms of action include modulation of steroid hormone receptors. We have investigated the effects of GLA with primary hormone therapy in an endocrine-sensitive cancer. Thirty-eight breast cancer patients (20 elderly Stage I-II, 14 locally advanced, 4 metastatic) took 8 capsules of oral GLA/day (total = 2.8 g) in addition to tamoxifen 20 mg od (T+GLA). Quality and duration of response were compared with matched controls receiving tamoxifen 20 mg od alone (n = 47). Serial tumour biopsies were taken to assess changes in oestrogen receptor (ER) and bcl-2 expression during treatment. GLA was well tolerated with no major side effects. T+GLA cases achieved a significantly faster clinical response (objective response vs. static disease) than tamoxifen controls, evident by 6 weeks on treatment (p = 0.010). There was significant reduction in ER expression in both treatment arms with T+GLA objective responders sustaining greater ER fall than tamoxifen counterparts (6-week biopsy p = 0.026; 6-month biopsy p = 0.019). We propose GLA as a useful adjunct to primary tamoxifen in endocrine-sensitive breast cancer. The effects of GLA on ER function and the apparent enhancement of tamoxifen-induced ER down-regulation by GLA require further investigation.

K-ras mutations, rectal crypt cells proliferation, and meat consumption in patients with left-sided colorectal carcinoma

It has been suggested that N-nitroso compounds derived from meat may increase the risk of K-ras mutations in the human colon. We sought evidence of associations between red meat consumption, frequency and type of K-ras mutations in resected tumours, and the rate of crypt cell proliferation (CCP) in the normal mucosa of patients with left-sided colorectal carcinoma. Meat consumption was assessed by food frequency questionnaire, and CCP was determined in rectal biopsies obtained prior to surgery. K-ras mutations in the resected tumours were determined using a PCR-based oligonucleotide hybridization assay. Fifteen K-ras mutations were detected in tumours from 43 patients; 13/15 in codon 12, 3/15 in codon 13, and 1/15 in both codons 12 and 13. All mutations were G-->A or G-->T transitions. There was no statistically significant difference between intakes of red meat in patients with a K-ras mutation (92.4 +/- 9.7 g/day) and those without (82.3 +/- 7.7 g/day). Rectal CCP was significantly higher in patients than in healthy controls, but there was no correlation with meat consumption or K-ras mutation. These data do not support the hypothesis that meat consumption is a risk factor for acquisition of K-ras mutations during colorectal carcinogenesis.

Immunohistochemical analysis reveals a tumour suppressor-like role for the transcription factor AP-2 in invasive breast cancer

This paper describes the generation and characterization of a monoclonal antibody specific for two members of the AP-2 family of transcription factors, AP-2alpha and AP-2beta, and its subsequent application to archival primary breast tumour material. Nuclear localization of AP-2 was found in all expressing cases, but in general levels of immunostaining were low, with only 17 per cent of the 86 tumours examined showing very high expression levels. Nevertheless, data analysis of the whole patient series allowed the identification of significant relationships between levels of AP-2 and other important breast markers. Thus, expression of AP-2alpha/beta was found to correlate significantly with expression of both ER ( p=0.036*) and the universal cell-cycle inhibitor p21(cip) ( p=0.03*), but was inversely related to levels of the proto-oncogene ErbB2 ( p=0.008*). AP-2-positive tumours also showed a low rate of proliferation, with significantly reduced mitotic count and a lower tumour grade. There was no significant relationship with clinical parameters, but samples with adjacent normal tissue indicated that loss of the AP-2 marker was associated with disease progression from normal breast through to invasive disease. This was confirmed by examining separate series of pure normal and pure DCIS samples, both of which expressed significantly higher levels of AP-2 ( p=0.0001* in each case) than the invasive tumours. Overall, these findings implicate AP-2alpha/beta as having a role akin to that of a tumour suppressor in breast cancer.

Consumption of fish oil leads to prompt incorporation of eicosapentaenoic acid into colonic mucosa of patients prior to surgery for colorectal cancer, but has no detectable effect on epithelial cytokinetics

Fish oil (FO) was previously reported to partially normalize colorectal crypt cell cytokinetics in patients with colorectal neoplasms. We determined the effect of FO on the fatty acid composition of colonic mucosa and mesenteric adipose tissue and on rectal crypt cell proliferation in patients undergoing surgery for colonic carcinoma. Patients (49-28 males; 21 females) were randomly assigned to consume FO capsules (2 g b.d.; FO group) containing 1.4 g eicosapentaenoic acid (EPA) and 1.0 g docosahexaenoic acid per day, or safflower oil capsules (2 g b.d.; placebo group) for an average of 12.3 +/- 0.5 d prior to surgery. Rectal biopsies were obtained at entry, at surgery, and 8-12 wk postsurgery. Colonic biopsies and samples of mesenteric adipose tissue were analyzed for fatty acids by gas-liquid chromatography. Mitosis was determined in whole crypt mounts. The proportion of EPA (g/100 g total fatty acids) in mucosal lipids was significantly greater in FO patients compared to the placebo group, but there was no effect on mesenteric adipose tissue. However self-reported use of FO supplements prior to surgery was associated with higher levels of EPA in adipose tissue. There was no significant effect of FO on the frequency or spatial distribution of crypt cell mitosis. EPA from marine oil supplements is rapidly incorporated into the colonic mucosal lipids of humans, but the levels achieved in the present study did not modify colorectal cytokinetics.

Involvement of steroid hormone and growth factor cross-talk in endocrine response in breast cancer

Multiple lines of evidence implicate steroid hormone and growth factor cross-talk as a modulator of endocrine response in breast cancer and that aberrations in growth factor signaling pathways are a common element in the endocrine resistant phenotype. Delineation of these relationships is thus an important diagnostic goal in cancer research, while the targeting of aberrant growth factor signaling holds the promise of improving therapeutic response rates.

Overexpression of cyclin D1 messenger RNA predicts for poor prognosis in estrogen receptor-positive breast cancer

Cyclin D1 is a key cell cycle regulatory protein with demonstrated oncogenic activity in a variety of malignancies. Cyclin D1 mRNA and protein are overexpressed in approximately 50% of primary breast carcinomas; however, the pathophysiological consequences of increased expression remain unclear. To investigate the functional sequelae of cyclin D1 mRNA overexpression, we analyzed clinical outcome in relation to the cyclin D1 mRNA level in 253 primary breast cancer patients (median follow-up, 75 months) with particular reference to estrogen receptor (ER) status and endocrine response. Overall, with the exception of the relationship between cyclin D1 mRNA expression and the ER, cyclin D1 mRNA was not associated with other clinicopathological features such as age, menopausal status, axillary lymph node status, vascular invasion, tumor size, type, and grade. However, in patients with ER-positive tumors (n = 182), high levels of cyclin D1 mRNA were associated with increased risk of relapse (P = 0.0016), local recurrence (P = 0.025), metastasis (P = 0.019), and death (P = 0.025). In contrast, there were no clinical correlations with cyclin D1 expression in ER-negative disease (n = 71). In 33 patients who received endocrine therapy for their primary or recurrent breast cancers, there was an apparent association between a high cyclin D1 mRNA level and a shorter response duration within the ER-positive subgroup (P = 0.04). Our findings indicate that overexpression of cyclin D1 mRNA correlates with a worse prognosis within the ER-positive breast cancer phenotype and may be a contributing factor to the development of endocrine resistance in ER-positive disease.

BRCA1 expression levels predict distant metastasis of sporadic breast cancers

The role of BRCA1 in progression of sporadic breast cancers has to date been equivocal, although preliminary studies on small numbers of samples have suggested an association between expression levels of this gene and acquisition of an invasive phenotype. We have further reasoned that loss of oestrogen receptor positivity may have a detrimental effect on BRCA1 expression. In order to test this hypothesis and extend earlier investigations we have applied a sensitive RT-PCR procedure to determine the associations between BRCA1 expression and a variety of clinical parameters in a sample cohort derived from sporadic breast tumour specimens. We have established that BRCA1 and ER mRNA expression are closely associated (p=0.013), indicating a possible functional relationship between these 2 genes. We have further identified an association between low levels of BRCA1 expression and acquisition of distant metastasis in sporadic disease (p=0.019). In light of our findings, we suggest that suppression of BRCA1 has a role to play in progression of a significant fraction of sporadic breast cancers and may additionally prove to be a useful, novel, prognostic marker for this disease type.

p21(WAF1) expression and endocrine response in breast cancer

An immunocytochemical assay for the p53-regulated protein product of the WAF1/Cip1 gene, p21(WAF1) (p21), was developed and applied to archival primary breast tumour material from 91 patients whose subsequent recurrent disease was treated with assessable courses of endocrine therapy. Nuclear localization of p21 protein was observed in 76 (82.4 per cent) cases. Status cut-offs were established and 29 (31.9 per cent) were deemed negative, 39 (42.9 per cent) weakly positive, and 23 (25.3 per cent) strongly positive. p21 status was inversely correlated with p53 protein (p=0.047) but did not relate to oestrogen receptor (ER) status, response to endocrine therapy, or time to further disease progression (TTP). Highly p21-positive patients had a significantly improved overall survival time (p=0. 020). Co-assessment of p21 and p53 subgroups revealed p21+/p53- patients to have good survival characteristics, whilst p21-/p53+ patients did poorly (p=0.008). The p21-/p53- patients overall did intermediately well, but Ki67-defined cellular proliferation analysis of these revealed two subclasses: those with high proliferation and poor survival times resembling the p21-/p53+ phenotype, and those with less proliferative tumours with good survival, similar to the p21+/p53- group. The significance of these results is discussed in the light of recent research concerning the role of p21 and p53 in breast cancer aetiology.

The immunohistochemical expression of desmoplakin and its role in vivo in the progression and metastasis of breast cancer

Desmoplakin (DP) is a protein located at the inner plaque of desmosomes where it associates with the desmosomal cadherins to form a cell adhesion complex. Reduced expression of DP has been correlated with the progression of several cancers, but its role in in vivo breast cancer is yet to be established. The aim of this present paper was to determine the immunohistochemical (IHC) expression of DP in breast cancer specimens (n = 75) in comparison with ductal carcinoma in situ (DCIS) (n = 26), tumour associated normal (n = 29) and normal breast tissue (n = 7). DP expression was correlated with that of desmosomal cadherin, Desmoglein 2 (Dsg2) and other clinical and IHC prognostic markers. DP staining occurred at the sub-plasma membrane level. There was no significant correlation between the level of DP (as assessed by the H-score) and that of Dsg. Significantly stronger staining was demonstrated in normal breast tissue and well differentiated tumours compared with more moderately or poorly differentiated tumours (P = 0.04). A significant inverse correlation was seen between DP staining and tumour size (P = 0.01). In a limited series of 8 cases, primary tumours demonstrated significantly stronger staining than the matched metastatic lymph nodes (P = 0.046). Of all the IHC markers examined, only Ki-67 showed a significant inverse relationship with DP staining (P = 0.01). In summary, the data suggest that loss of DP may be of potential importance in progression of breast cancer in vivo from normal, DCIS, well differentiated through to poorly differentiated, large tumours. In addition, this loss may be associated with metastasis.

Endocrine response and resistance in breast cancer: a role for the transcription factor Fos

We have previously demonstrated that elevated Fos expression may be important in de novo endocrine resistance in breast cancer. However, changes in Fos expression during endocrine response and subsequently on acquisition of resistance are unknown. This study immunocytochemically monitors Fos protein within sequential biopsies from primary human breast cancer patients obtained pre-treatment (T1), during tamoxifen therapy (T2, T3) and on disease progression (T5), examining in parallel proliferation [i.e., MIBI (Ki67) immunostaining, mitotic activity], cellularity and endocrine response. Significantly diminished Fos, proliferation and cellularity were observed after 6 weeks of therapy in patients exhibiting a better quality and/or duration of response, while modest Fos increases and a maintained proliferation and cellularity were seen in poorer responders. Decreases in Fos, proliferation and cellularity at 6 months similarly hallmarked better responders. We confirmed a significant association between de novo resistance and elevated Fos and proliferation. Additionally, however, these parameters increased at the time of disease relapse over pre-treatment and "on therapy" values. Our data indicate that tamoxifen response involves a reduction in both tumor cell proliferation and cell survival, potentially entailing diminished Fos protein expression in better-responding patients. Our data are also supportive of elevated Fos expression being involved in the departure from endocrine control inherent in both primary and acquired resistance.

c-erbB3 and c-erbB4 expression is a feature of the endocrine responsive phenotype in clinical breast cancer

We examined c-erbB3 and c-erbB4 mRNA expression in 47 primary breast cancer samples by simultaneous RT-PCR and have investigated correlations between these parameters and the expression of both ER and EGFR mRNA and protein as measured by RT-PCR and ICA and with Ki67 immunostaining. A direct association was found between c-erbB3 and c-erbB4 mRNA and ER marker status measured by either RT-PCR (c-erbB3 P = 0.0003; c-erbB4 P = 0.02) or ICA (c-erbB-3 P = 0.002; c-erbB4 P = 0.01). Inverse associations were seen between c-erbB3 and c-erbB4 mRNA marker status and EGFR membrane protein (c-erbB3: P = 0.003; cerbB4: P = 0.003) and mRNA (c-erbB4: P = 0.009) status. These associations were reinforced by Spearman Rank Correlation Tests. A significant relationship was seen between Ki67 and c-erbB4 mRNA status and level. Measurements of c-erbB3 protein levels in tumour samples removed from a further 89 patients of known response to endocrine therapy: (i) confirmed the relationship between c-erbB3 and ER and (ii) identified that patients whose ER positive tumours expressed high levels of c-erbB3 were most likely to benefit from endocrine measures. A non-significant trend was recorded between c-erbB3 levels and Ki67 immunostaining. These results clearly demonstrate that increased c-erbB3 and c-erbB4 expression appears to be associated with the prognostically-favourable ER phenotype.

C-erbB2 expression predicts response to preoperative chemotherapy for locally advanced breast cancer

BACKGROUND

Previous work suggests that the presence of c-erbB2 oncoprotein immunostaining and the proliferation rate of tumours, may be relevant to chemo-sensitivity in breast cancer.

PATIENTS AND METHODS

To investigate this we assessed pretreatment biopsies from 50 patients with locally advanced breast cancer for expression of c-erbB2 and MIB1 (proliferative marker) in relation to clinical response after 3 months preoperative chemotherapy.

RESULTS

Objective response was significantly more likely (22/30, 73%) for tumours negative for c-erbB2 membrane staining, compared to positively staining tumours (6/20, 30%, p = 0.0025). The percentage of cells staining positively for MIB1 was not predictive of response (p = 0.56).

CONCLUSIONS

This study has shown an increased likelihood of response to preoperative chemotherapy for breast cancers negative for c-erbB2 staining. Previous studies have shown that c-erbB2 immunostaining can correlate with either chemo-resistance or chemo-response. We postulate that this conflict may be due to differences in the type of chemotherapy administered. This raises the possibility of biological markers being use to assist in the selection of the type of chemotherapy regimen administered to particular tumour biological phenotype.

Quercetin glucosides interact with the intestinal glucose transport pathway

Flavonols are efficient antioxidants with the potential to protect biological macromolecules from oxidative damage in vivo, and if absorbed into the circulation they may protect against cardiovascular disease. Although flavonol aglycones are present in foods at low concentrations, their glycosides are abundant in onions, apples, beans and tea, and are thought to be stable under the conditions of the human stomach and small bowel. There is, however, recent evidence to suggest that intact glycosides of quercetin may be absorbed from the small intestine by a mechanism involving the glucose transport pathway. In the present study we tested this hypothesis by measuring the effect of quercetin glycosides on the rate of efflux of galactose from the jejunal mucosa. Everted sacs of rat jejunum preloaded with 14C-galactose were exposed to quercetin glycosides isolated from onions. Quercetin mono- and diglucosides were shown to accelerate the carrier-mediated efflux of galactose via a sodium-dependent pathway. HPLC analysis confirmed the stability of the glycosides under conditions simulating those in the upper alimentary tract. These studies suggest that purified quercetin glucosides are capable of interacting with the sodium dependent glucose transport receptors in the mucosal epithelium and may therefore be absorbed by the small intestine in vivo.

Oestrogen-regulated genes in breast cancer: association of pLIV1 with response to endocrine therapy

Northern hybridization analyses of the oestrogen-inducible mRNAs pLIV1 and pS2 were compared with oestrogen receptor (ER) immunocytochemistry assessments in 40 untreated primary or early recurrent breast tumours. Significant associations were observed between pLIV1/ER (P < 0.03), pS2/ER (P < 0.001) and pLIV1/pS2 (P < 0.04) status. After disease recurrence, patients were treated with assessable courses of endocrine therapies. Positive pLIV1, pS2 and ER statuses in primary disease were consequently found to be predictive of endocrine responsiveness in the secondary lesions (P < 0.03, P < 0.02, P < 0.005 respectively). However, despite these associations, a number of pLIV1- and/or pS2-positive tumours failed to respond to therapy.

Use of reverse transcription-polymerase chain reaction methodology to detect estrogen-regulated gene expression in small breast cancer specimens

We describe the development and use of a sensitive reverse transcription-PCR (RT-PCR) procedure to detect novel estrogen-regulated gene expression in small clinical breast cancer samples, in which such study would be extremely difficult by any other molecular or immunocytochemical means. Assay optimization for pLIV1, estrogen receptors (ERs), progesterone receptors, and pS2 gene products was carried out on 50 primary breast cancers for which comparative Northern analysis and immunocytochemical data were available. Using 27 amplification cycles and a 0.5 microM primer concentration, varying expressions of the gene products were recorded simultaneously with a constant densitometric signal for a coamplified endogenous control gene (alpha-actin). Good concordances were subsequently observed between pLIV1 status generated by RT-PCR and both Northern analysis (P = 0.002) and ER status by immunocytochemistry (P = 0.0244). Agreement was also noted between ER (P = 0.002), progesterone receptor (P = 0.0005), and pS2 (P = 0. 0023) RT-PCR and immunocytochemical methodologies. The RT-PCR assays were then applied to 10 needle core trucut biopsies in which similar relationships were obtained. Our results justify the future use of this RT-PCR methodology to examine new estrogen-regulated genes in small breast cancer samples, and it is envisaged that this technology will prove invaluable in many future breast cancer studies.

Soluble non-starch polysaccharides derived from complex food matrices do not increase average lipid droplet size during gastric lipid emulsification in rats

The creation of a finely dispersed lipid emulsion is essential for efficient hydrolysis of dietary triglycerides. The effectiveness of emulsification within the stomach depends upon the shear force generated by gastric motility and the concentration of emulsifiers present in the gastric contents. Other dietary constituents can modify these factors, and previous studies have suggested that the presence of soluble non-starch polysaccharides (NSP) during digestion might increase the average size of intraluminal emulsion droplets. In the present study, we developed a new technique for the isolation and analysis of intraluminal lipid emulsions by optical diffraction analysis. The method was applied to rats fed powdered semipurified diets that were free of all NSP or supplemented with insoluble cellulose, guar gum, or NSP derived from apple, carrot or rolled oats. Cellulose had no significant effect on emulsion size, and there was no evidence that the average sizes of lipid droplets in the gastric fundus or antrum were higher than control values in rats fed diets supplemented with any source of soluble NSP. In the groups fed oats and cooked carrot NSP, the mean droplet diameters approached half the values for diets free of NSP or containing insoluble cellulose. The difference between rats fed NSP from cooked carrot and those fed cellulose was significant in the proximal stomach (P < 0.05), and that between rats fed raw oats and rats fed cellulose was significant in the distal stomach (P < 0.05). Soluble dietary fiber does not inhibit lipid or cholesterol absorption via any inhibition of lipid emulsification.

Comparative studies of the mitogenic effects of epidermal growth factor and transforming growth factor-alpha and the expression of various growth factors in neoplastic and non-neoplastic prostatic cell lines

BACKGROUND

The role of growth factors in prostate cell growth has been investigated as these peptides may be involved in the autonomous growth of hormone-independent prostate cancer.

METHODS

Responses of neoplastic (PC-3 and CPA) and non-neoplastic (CAPE) prostatic cell lines to epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) were determined using clonogenic and growth curve analysis. The constitutive expression of EGF, TGF-alpha, and TGF-beta 1-3 mRNA was examined using Northern blotting and EGF and TGF-alpha protein levels were determined immunohistochemically.

RESULTS

Growth curve and clonogenic analysis indicated that EGF and TGF-alpha were mitogenic in each cell line. The magnitude of the clonogenic response varied between the cell lines, with CPA cells showing the greatest growth increases. CPA cells also displayed the highest levels of EGF and TGF-alpha mRNA and protein. TGF-beta 1 mRNA was detected in the order of magnitude, PC-3 > CPA > CAPE. Furthermore, PC-3 and CPA cells expressed TGF-beta 3 and TGF-beta 2 transcripts respectively. In each cell line, the expression of any growth factor mRNA was not affected by exogenous EGF.

CONCLUSIONS

The growth responses of the cell lines to EGF and TGF-alpha did not correlate with their constitutive levels of EGF and TGF-alpha mRNA and protein, thus whilst growth factors may be important in malignant cell growth, other pathways may also be involved in the autocrine regulation of cell proliferation.

Effect of saponin on the transmucosal passage of beta-lactoglobulin across the proximal small intestine of normal and beta-lactoglobulin-sensitised rats

The ability of saponins and glycoalkaloids to permeabilise the mammalian intestinal barrier has been previously demonstrated in vitro, leading to the hypothesis that membranolytic saponins may facilitate transfer to the tissues of otherwise excluded macromolecules. An enhanced uptake of, for instance, potentially allergenic species from the lumen is one of the factors that may affect the induction of food allergy, and its presentation in already sensitised individuals. In the experiments described here, an increase in the transmucosal uptake of the milk allergen beta-lactoglobulin (beta LG) was assessed in non-sensitised and sensitised Brown Norway rats in the presence of Gypsophila saponin. Isolated jejunal loops were exposed in vivo to either beta LG followed by saponin, saponin followed by beta LG or the two compounds simultaneously. Portal vein blood samples were collected and assayed for beta LG and rat mucosal mast cell protease (RCMP II) activity. Mucosal tissue was also examined histologically and assayed for histamine content. Sham-operated animals, exposed to physiological buffer alone, were included as controls and beta LG measurements corrected for this component which was negligible. No transfer of beta LG occurred in the absence of saponin in non-sensitised rats, whereas a significant enhancement was observed in the presence of saponin. beta LG was detected in the portal circulation of sensitised rats exposed to beta LG alone; however addition of saponin to the intestinal lumen further enhanced this uptake, possibly by an independent mechanism. Histological examination of the mucosal epithelium exposed to saponin revealed damage, especially at the villus tips. Mucosal histamine and serum RCMP II concentrations were consistent with the differences observed between sensitised and non-sensitised animals. It is concluded that exposure to food constituents capable of permeabilising the mucosal epithelium may increase the risk of sensitisation to dietary antigens.

Fermentable carbohydrate modulates postprandial enteroglucagon and gastrin release in rats

We studied the effects of a fermentable sugar-alcohol (lactitol) on the concentrations of enteroglucagon and gastrin in the blood of rats for 7.5 h after feeding. The control and treatment groups were fed on semi-purified diets containing either non-fermentable cellulose or lactitol respectively, at 100 g/kg. Compared with the cellulose-fed group, the animals fed with lactitol had higher levels of enteroglucagon (5-10 times higher than control; P < 0.05) and lower serum gastrin (70-80% of control; P < 0.05) for several hours after the withdrawal of feed. In contrast, varying the level of dietary lipid (maize oil) over a range of 8-120 g/kg had no effect on the release of either peptide. These results suggest that poorly absorbed fermentable dietary carbohydrate stimulates postprandial plasma enteroglucagon and inhibits serum gastrin release in the rat. The mechanism is uncertain but an endocrine response by the colon to fermentation products seems probable.