I. F. Stamford

Metabolites of arachidonic acid formed by human gastrointestinal tissues and their actions on the muscle layers.

1 Gas chromatography‐mass spectrometry demonstrated the presence of arachidonic acid (AA), 6‐keto‐prostaglandin F1α and thromboxane B2 (TxB2) in all extracts of homogenized muscle or mucosa from human stomach, terminal ileum or sigmoid colon. Prostaglandin D2 (PGD2), PGE2 or PGF2α were usually found more often in the mucosal extracts. The 12‐hydroxy‐derivative of AA (12‐HETE) was detected in all extracts of the colon but in only some of the other tissues 2 Most prostanoids tested contracted the longitudinal muscle, the order of potency being U‐46619 (an epoxymethano analogue of PGH2)>PGE2>PGF2α>PGD2; PGI2 usually caused relaxation, whereas its breakdown products or TxB2 had weak and variable effects 3 U‐46619 or, less potently, PGF2α contracted the circular muscle, whereas PGI2 and usually PGE2 caused relaxation. PGD2, 6‐keto‐PGF1α, 6, 15‐diketo‐PGF1α or TxB2 usually had little or no effect 4 PGI2 antagonized contractions to some excitatory prostanoids, without greatly affecting contractions to acetylcholine 5 For both muscle layers there was a gradient in sensitivity to prostanoids along the gastrointestinal tract. The sensitivities were stomach>distal ileum>sigmoid colon 6 The results are discussed in relation to gastrointestinal physiology and pathophysiology.

Cancer growth, response to treatment and survival time in mice: beneficial effect of the prostaglandin synthesis inhibitor flurbiprofen.

Adult mice were injected subcutaneously with cells from a syngeneic metastasizing mammary cancer. Daily treatment with flurbiprofen starting before injection of the cancer cells reduced tumour growth and lengthened the survival of mice whose tumours were excised at 3 weeks. When low doses of radiotherapy and chemotherapy were given, additional treatment with flurbiprofen starting 25 days after injecting the cancer cells substantially inhibited tumour growth.

Estimation and characterization of prostaglandins in the human gastrointestinal tract.

1 Prostaglandin‐like material was extracted from muscle and mucosa of surgically removed human stomach, ileum and colon and assayed against prostaglandin E2 on strips of rat gastric fundus. Superfused human isolated gastric mucosa released prostaglandin‐like material and release was increased by stretching or clamping the tissue. 2 The relative amounts of extracted biological activity were broadly as follows: gastric antral mucosa > colon muscle > gastric body mucosa ≅ ileal mucosa > colon mucosa ≅ gastric muscle ≅ ileal muscle. 3 Prostaglandin E and F were tentatively identified by chromatography and sensitivity to inactivation by alkali. 4 Prostaglandin E apparently contributed most to the biological activity, possibly because the assay tissue is more sensitive to prostaglandin E than to F. Chromatography of gastric body mucosal extracts located material running with prostaglandin E2 and a little with E1. Colonic muscle and mucosal extracts contained material with RF values of prostaglandins E1, E2, E3 and F1α, whereas F2α and F3α‐like substances were found only in the mucosa. The proportions of prostaglandin F varied between specimens. 5 The amount of extracted prostaglandin‐like activity was increased by adding cofactors and arachidonic acid, and lessened by homogenization with acid‐ethanol. 6 The type and amount of activity generated from arachidonic acid by partly purified colonic mucosal prostaglandin synthetase depended on the substrate concentration. 7 The possible relationships of prostaglandins to mucus secretion and other physiological and pathological gut functions are discussed.

Bone destruction by breast tumours

Abstract In 1975 we reported preliminary evidence that normal human breast tissue and benign breast tumours contain and synthesise little PG- like material, whereas malignant breast tumours contain significantly more. Those tumours synthesising most PG were associated with spread to bone (1), possibly because some PGs are potent bone resorbing agents (2,3). Our further data re-inforce the correlation between tumour PG levels and the incidence of bone metastases.

Studies on the mechanism by which indomethacin increases the anticancer effect of methotrexate

1 The effect of indomethacin on the response of the NC carcinoma to methotrexate has been examined in vivo and in vitro. 2 Survival was prolonged in mice treated with indomethacin 1.25 mg kg−1 twice daily plus methotrexate 4 mg kg−1 daily, compared to mice given either drug alone or controls. 3 Indomethacin 1 μg ml−1 increased the killing of cultured NC cells by methotrexate. This was not due to displacement of methotrexate from binding sites on the serum proteins. Nor was it due (entirely) to inhibition of prostaglandin synthesis, since flurbiprofen did not mimic the effect. Inhibition of cyclic AMP phosphodiesterase seems unlikely to explain the effect of indomethacin since theophylline had little or no effect on NC cell killing by methotrexate. 4 Indomethacin 1 μg ml−1 increased the accumulation of tritium in NC cells incubated with [3H]‐methotrexate. 5 In contrast, with normal epithelial cells from human embryonic intestine, indomethacin 1 μg ml−1 did not alter the cytotoxicity of methotrexate or the accumulation of tritium during incubation with [3H]‐methotrexate. 6 The beneficial interaction between indomethacin and methotrexate may have therapeutic potential in man.

Studies of three non-peptide cholecystokinin antagonists (devazepide, lorglumide and loxiglumide) in human isolated alimentary muscle and guinea-pig ileum

1 Three recently described non‐peptide cholecystokinin (CCK) antagonists (devazepide, lorglumide, loxiglumide) have been studied for their antagonism of the contraction to cholecystokinin‐octapeptide (CCK‐OP) in human alimentary muscle and guinea‐pig intestine. 2 Each antagonist caused a concentration‐dependent inhibition of the contraction induced by CCK‐OP, regardless of regional and species differences. 3 The potencies of each drug, estimated by use of an adaptation of the Cheng & Prusoff equation, were similar in the different regions of human alimentary tract (weighted mean apparent pKB, ± s.e.mean: devazepide, 5.76 ± 0.08, n = 20; lorglumide, 5.82 ± 0.04, n = 25; loxiglumide, 5.87 ± 0.07, n = 24). 4 In contrast, the potencies differed markedly in the guinea‐pig ileum. Apparent pKB values obtained by the same method as with human tissues were, mean ± s.e.mean: devazepide, 10.61 ± 0.61; lorglumide, 7.43 ± 0.20; loxiglumide, 6.67 ±0.12. pKB values obtained from classical competition experiments were: devazepide, 10.09 ± 0.09; lorglumide 7.70 ± 0.12; loxiglumide 6.08 ± 0.22. 5 The CCK receptors in human gut muscle from different regions seem to be similar, but there appear to be species differences.

Treatment of mouse carcinoma in vivo with a prostaglandin E2 analogue and indomethacin

WHT/Ht mice transplanted s.c. with NC carcinoma were treated with 16,16-dimethyl prostaglandin E2 methyl ester (di-me-PGE2) and/or indomethacin. Each primary tumour was excised under anaesthesia 3 weeks after transplantation, weighed and extracted for prostaglandins. Mouse survival time and tumour recurrence were measured. Di-me-PGE2 10 micrograms, injected at the tumour site on alternate days from day 1 to 19, indomethacin 2.5 mg kg-1 daily by mouth, or both drugs together resulted in lighter tumours (respectively 45, 45 and 52% less, n = 18 to 20 per group, P less than 0.02) compared with vehicle-treated controls. Indomethacin reduced the tumour prostaglandin yield, but the biological activity in extracts of tumours from mice given di-me-PGE2 was high. The median survival time was longer in mice receiving indomethacin alone (61 days from tumour transplantation compared with 50 days in controls P less than 0.02). Di-me-PGE2 alone had little or no effect on survival (median 48 days) but counteracted the increase with indomethacin (di-me-PGE2 + indomethacin, 49 days median survival). There were no obvious effects of the treatments on tumour recurrence at the excision site, but there was a higher incidence of involved lymph nodes in mice given di-me-PGE2.WHT/Ht mice transplanted s.c. with NC carcinoma were treated with 16,16-dimethyl prostaglandin E2 methyl ester (di-me-PGE2) and/or indomethacin. Each primary tumour was excised under anaesthesia 3 weeks after transplantation, weighed and extracted for prostaglandins. Mouse survival time and tumour recurrence were measured. Di-me-PGE2 10 micrograms, injected at the tumour site on alternate days from day 1 to 19, indomethacin 2.5 mg kg-1 daily by mouth, or both drugs together resulted in lighter tumours (respectively 45, 45 and 52% less, n = 18 to 20 per group, P less than 0.02) compared with vehicle-treated controls. Indomethacin reduced the tumour prostaglandin yield, but the biological activity in extracts of tumours from mice given di-me-PGE2 was high. The median survival time was longer in mice receiving indomethacin alone (61 days from tumour transplantation compared with 50 days in controls P less than 0.02). Di-me-PGE2 alone had little or no effect on survival (median 48 days) but counteracted the increase with indomethacin (di-me-PGE2 + indomethacin, 49 days median survival). There were no obvious effects of the treatments on tumour recurrence at the excision site, but there was a higher incidence of involved lymph nodes in mice given di-me-PGE2.

The effects of various peptides on human isolated gut muscle

Abstract— The effects of eleven peptides of gastrointestinal origin have been studied on the contraction, relaxation and spontaneous activity of circular and longitudinal muscle strips from different regions of the human gastrointestinal tract. The effects varied with the peptides and sometimes with the region and muscle layer. There was either contraction, no effect, or relaxation and/or inhibition of an acetylcholine‐induced contraction. Responses to some peptides are consistent with the possibility that they may contribute directly to the control of motility: galanin, neurotensin and substance P might be involved in contraction, and vasoactive intestinal peptide, peptide histidine isoleucine and peptide histidine methionine might be inhibitory transmitters.

The effects of cholecystokinin octapeptide on human isolated alimentary muscle.

1 We studied cholecystokinin octapeptide (CCK‐OP) for its motor effects and sites of action on human isolated muscle from stomach, small intestine and colon. 2 CCK‐OP induced a concentration‐dependent contraction of all the longitudinal muscles and of circular muscle from the stomach and large intestine. The peptide acted directly on these muscles at a site not involving muscarinic receptors. 3 CCK‐OP relaxed the circular muscle of the small intestine and/or reduced the contractions to acetylcholine, by stimulating intramural postganglionic inhibitory neurones.

Carbenoxolone and deglycyrrhized liquorice have little or no effect on prostanoid synthesis by rat gastric mucosa ex vivo.

1 Rats were given either carbenoxolone 50 mg kg−1, deglycyrrhized liquorice 1 g kg−1 or vehicle by gastric tube. The doses were repeated 16 h later, and the stomachs removed after another 2 h. 2 The amounts of prostaglandin E (PGE), 6‐keto‐PGF1α and thromboxane B2, measured by radioimmunoassay in extracts of the gastric corpus and antrum mucosa, were similar in the treated animals and the controls. 3 We conclude that in rats, carbenoxolone and deglycyrrhized liquorice may exert their anti‐ulcer effect by a non‐prostaglandin mechanism. This contrasts with the mechanism thought to occur in man with carbenoxolone.