OCCURRENCE OF PROSTAGLANDIN E2 IN THE HUMAN STOMACH, AND A STUDY OF ITS EFFECTS ON HUMAN ISOLATED GASTRIC MUSCLE

We have previously shown the presence of an unidentified smooth-muscle stimulating factor in human stomach mucosa (Murray & Wyllie, 1964, 1965).The work described in the present paper has shown that the material is prostaglandin E2 (PGE2) and that it is present in moderately high concentration.We have also found that PGE1 is remarkably active on human stomach muscle, a tissue generally unreactive to pharmacological agents (Bennett & Whitney, 1966). METHODS MaterialExcised portions of human stomach, taken at least 6 cm from any macroscopic pathological lesion, were obtained fresh in the operating theatre.They were taken in cold Krebs solution to the laboratory where the mucosa and submucosa were dissected from the muscle.The mucosa was either extracted immediately or was stored at -200 C, usually for less than a week.The muscle was studied the same day or was stored overnight in Krebs solution at 4' C. Extraction procedureExtracts were made initially with 80% acetone by the method of Parratt & West (1957) and subsequently by the method of Samuelsson (1963).The latter procedure involves ethanol extraction followed by partition firstly between diethyl ether and an aqueous phase acidified to pH 3, and secondly between petrol and aqueous ethanol.Parallel experiments showed that the initial stages of the two methods yielded approximately equal amounts of prostaglandins from the same sample of mucosa.In a few experiments tissues were extracted with Krebs solution by homogenization in a Potter-Elvehjem homogenizer or by grinding with sand. ChromatographyChromatography of acetone extracts on Whatman No. 1 paper with butanol:acetic acid:water (60:15:25 vol.) was used to separate prostaglandins from 5-hydroxytryptamine.The E and F series of prostaglandins were separated by the method of Samuelsson (1963), using a 1 g column of silicic acid, and were also distinguished by thin layer chromatography using the solvent Al of Green & Samuelsson (1964).Plates impregnated with silver nitrate (0.5 g AgNO3/15 g silica gel G, Mallinkrodt) were used with solvent system All of Green & Samuelsson (1964) to distinguish prostaglandins with different numbers of double bonds.