BRITISH MEDICAL JOURNAL
`
`20 JANUARY 1973
`
`143
`
`Effect of Orally Administered Prostaglandin E2 and its
`15-Methyl Analogues on Gastric Secretion
`
`S. M. M. KARIM, D. C. CARTER, D. BHANA, P. ADAIKAN GANESAN
`
`British Medical Journal, 1973, 1, 143-146
`
`Summary
`The effect of orally administered prostaglandin E2 and
`its synthetic 15-methyl analogues on gastric secretion in
`man was studied. The parent E, compound did not
`inhibit basal secretion,whereas both the 15 (S) 15-methyl-
`E, methyl ester and its isomer, 15 (R) 15-methyl-E,
`methyl ester inhibited basal acid secretion. This action is
`likely to be a direct one on the parietal cell, and it could
`prove of value in the treatment of peptic ulcer.
`
`Introduction
`The inhibition of gastric acid secretion in man by intravenous
`infusion of prostaglandins El (PGE,), E2 (PGE,), and Al
`(PGA1) has been reported by several investigators (Classen
`et al., 1970; Wada and Ishizawa, 1970; Wilson et al., 1971).
`While PGE1 in contact with gastric mucosa inhibited acid
`production in anaesthetized rats (Ramwell and Shaw, 1968)
`and in isolated bullfrog mucosa preparations (Way and Durbin,
`1969) there have been no reports of locally administered prostag-
`landins having a similar effect in man. On the contrary, Horton
`et al. (1968) found that in man orally administered PGE1 had no
`effect on pentagastrin-induced acid secretion.
`A possible explanation for the lack of effect of orally ad-
`ministered naturally occurring prostaglandins on acid secretion
`is their rapid enzymatic inactivation and metabolism. One of the
`most important points in the metabolism of naturally occurring
`dehydrogenation at carbon 15, which is
`prostaglandins is
`brought about by the enzyme prostaglandin 15-OH dehydro-
`genase. This metabolism occurs very readily and the resulting
`compounds possess a greatly reduced biological activity. Prost-
`aglandin analogues modified at carbon 15 have now been
`synthesized (Bundy et al., 1971; Yankee and Bundy, 1972).
`Two such compounds are prostaglandin 15 (S) 15-methyl-E,
`methyl ester and its isomer 15 (R) 15-methyl-E2 methyl ester
`(fig. 1). These analogues are not substrates for enzyme prostag-
`landin 15-OH dehydrogenase and consequently enzymic de-
`gradation at carbon 15 is prevented. The increase in some of the
`biological actions of analogues with modification at carbon 15
`has been confirmed (Karim and Sharma, 1972; Karim et al.,
`1972a; Kirton and Forbes, 1972).
`The present study was undertaken to assess the effect of
`PGE2 and its synthetic analogues 15 (S) 15-methyl-E, methyl
`ester and 15 (R) 15-methyl-E, methyl ester on basal human
`gastric acid secretion when administered orally to normal
`healthy male volunteers. This screening study represents only
`one part of a larger survey, but because of the implications of the
`early results it was considered of value to publish them in this
`preliminary form.
`
`Makerere University Medical School, P.O. Box 7072, Kampala,
`Uganda
`S. M. M. KARIM, PH.D., Professor of Pharmacology
`D. C. CARTER, F.R.C.S., Lecturer in Surgery
`D. BHANA, F.R.C.S., Senior Lecturer in Surgery
`P. ADAIKAN GANESAN, Senior Research Technician in Pharmacology
`
`0
`
`10.*'\_
`
`0
`
`OH
`
`~~HO
`
`COOCH
`-0
`
`12 . '
`
`PG l(R) 1-mI
`COOH
`b20
`
`~17
`
`19
`
`PG E2
`
`PG15H3( -EPG 15(R) 15-me-E2
`
`me Ester
`
`OH
`
`3O~OH"
`
`0
`
`PG15 (S) 15-me-E2
`--.me Ester
`
`COH
`
`OH
`
`HO
`
`CH3
`
`FIG. 1-Chemical structure of prostaglandin E2 and synthetic analogues
`15 (R) 15-methyl-E2 methyl ester and 15 (S) 15-methyl-E2 methyl ester.
`
`Materials and Methods
`A total of 26 tests were carried out in healthy male volunteers
`using the above prostaglandins. In 7 tests the parent PGEs was
`given orally, in 15 tests the 15 (R) analogue was given orally,
`and in the remaining 4 tests the 15 (S) analogue was similarly
`administered. For 20 of these tests data were available from
`control studies in the same individuals where the vehicle was
`given without the prostaglandin.
`After a 12-hour overnight fast a nasogastric tube (F.G. 14-16)
`was passed into the stomach. The fasting residue was discarded
`and the tube position adjusted to allow the ready recovery of a
`trial 20 ml instillate of water. Although continuous suction was
`applied tube patency was also ensured by periodic air insuffla-
`tion. Specimens of gastric juice were collected every 15 minutes
`and assessed in terms of volume (ml), pH, acid concentration
`(mEq/l.), and acid output (mEq). Titrations were performed to
`end-point pH 7 by using a glass electrode and 0-05N NaOH
`solution. After a basal period of two 15-minute collections the
`prostaglandin was given by instillation down the nasogastric
`tube in 10 ml of water. Aspiration was discontinued for 30
`minutes to allow contact with the gastric mucosa. Collection
`was then restarted for a further three hours. The control studies
`differed only in that prostaglandins were excluded from the
`instillate.
`Subjects were questioned specifically about untoward gastro-
`intestinal and other side effects during the test and asked to
`report any alterations in bowel habit in the succeeding 24
`hours.
`
`Results
`
`PROSTAGLANDIN E2
`Of the seven tests carried out with the parent compound three
`were performed using 2-5 mg orally and four with a dose of
`4 mg. In view of the recognized side effects of oral PGE2 it was
`deemed unwise to use a higher dosage (Karim, 1971). In none of
`the tests was a consistent or even transient inhibition of acid
`secretion obvious either in absolute terms or relative to the
`
`

`
`144
`Comparison between Acid Output in Control Studies and Output after Locally Administered Prostaglandins
`
`BRITISH MEDICAL JOURNAL
`
`20 JANUARY 1973
`
`Dose of Prostaglandin
`
`2-5 mg (1 test):
`Prostaglandin.
`Control.
`4 0 mg (3 tests):
`Prostaglandin.
`Control.
`
`100 ,ug (3 tests):
`Prostaglandin.
`Control.
`150 jig (2 tests):
`Prostaglandin.
`Control.
`200 ,ug (5 tests):
`Prostaglandin.
`Control.
`
`25 ,ug (2 tests):
`Prostaglandin.
`Control.
`50 tg (2 tests):
`Prostaglandin.
`Control.
`
`Effect of Prostaglandin on Mean Hourly Acid Output (mEq/hr)*
`2nd Hour
`3rd Hour
`1st Hour
`PGE2
`2-98 (51)
`3-41 (99)
`2-83 (91)
`1-83 (69)
`15 (R) 15-methyl-E2 Methyl Ester
`1-95 (65)
`2-02 (62)
`0-42 (49)
`1-99 (77)
`0-44 (98)
`2-24 (85)
`15 (S) 15-methyl-E2 Methyl Ester
`1-63 (86)
`1-94 (77)
`0-01 (66)
`1-28 (35)
`
`4-98 (108)
`2-41 (126)
`2-99 (128)
`2-28 (92)
`
`2-17 (96)
`3-38 (113)
`0-67 (59)
`406 (96)
`0-63 (104)
`3-08 (99)
`
`070 (68)
`406 (96)
`040 (90)
`5-32 (95)
`
`Effect of Prostaglandin on Mean
`Three-hour Acid Outputt
`
`10-56 (251)
`7 90 (325)
`8-66 (279)
`5-68 (231)
`
`6-50 (214)
`7 70 (238)
`2-11 (176)
`7-57 (226)
`1-71 (283)
`8 09 (259)
`
`4-27 (232)
`7-57 (226)
`1-47 (225)
`8-12 (172)
`
`2 60 (92)
`2-08 (100)
`2-83 (60)
`1-57 (70)
`
`2-48 (53)
`3-31 (63)
`1-02 (67)
`1-52 (53)
`0-65 (81)
`2-73 (75)
`
`1-94 (78)
`1-51 (54)
`1-06 (70)
`1-52 (42)
`
`Mean hourly volume of aspirate is given in parentheses.
`tMean total volume of aspirate is given in parentheses.
`
`control data available for four of the subjects (see table). No
`side effects were reported from the use of this compound at
`these dose levels.
`
`for 90 minutes after instillation. In the two subjects where
`control data were available the three-hour output after prostag-
`landin was 51 6% and 7-8% respectively of the control values.
`
`3
`
`PG 15 (R) 15-me- E2me Ester
`
`a E
`
`09 2
`
`-E
`
`m
`
`._-
`
`u
`
`PROSTAGLANDIN 15 (R) 15-METHYL-E2 METHYL ESTER
`Dose 100 sg (5 tests).-As shown in fig. 2 the acid output in
`mEq/30 min fell in all cases after instillation of the prostag-
`landin. In three subjects the reduction was marked and sustained
`for the duration of the test, whereas in one subject the output
`rose again to basal levels within one hour of restarting aspiration.
`3
`
`01 s
`0
`BoasalI
`
`2
`Time (hr)
`
`3
`
`4
`
`FIG. 3-Effect of oral dose of 150 pLg prostaglandin 15 (R) 15-methyl-E,
`methyl ester on basal acid secretion.
`
`Dose 200 Fg (7 tests).-Five of the seven tests carried out with
`200 ILg of the analogue showed a profound and sustained
`reduction in acid production, the aspirate remaining alkaline
`for at least 120 minutes (fig. 4). In the other two tests a marked
`fall in acid secretion was also noted but the pH did not rise
`above 7 in either case. Control data were available for five ofthese
`tests and the comparison with the acid output after prostag-
`landin is summarized in the table. The reduction in mean three-
`hour acid output effected by this dose of prostaglandin was
`again achieved by a fall in acid concentration while the volume
`of aspirate appeared unaffected.
`No untoward side effects were noted during or in the 24 hours
`after any of the tests using the 15 (R) 15-methyl-E, methyl ester.
`
`PROSTAGLANDIN 15 (s) 15-METHYL-E2 METHYL ESTER
`Dose 25 iLg (2 tests).-In both tests a transient fall in acid
`output was observed (fig. 5), and although the aspirate became
`
`aE a
`
`'
`*u
`E
`
`0
`Basal
`
`2
`Time (hr)
`
`3
`
`4
`
`FIG. 2-Effect of oral dose of 100 tg prostaglandin 15 (R) 15-methyl-E.
`methyl ester on basal acid secretion.
`
`A repeat test in this individual showed a similar pattern of
`secretion. The fall in output in all cases was due primarily to a
`reduction in the acidity rather than volume of secretion. The
`comparison of the acid output after prostaglandin with control
`values is summarized in the table.
`Dose 150 jig (3 tests).-In the three individuals tested at this
`dose level inhibition of acid secretion was noted in all cases
`(fig. 3). As with the lower dose the effect was mediated pri-
`marily by a reduction in acid concentration and was reflected in a
`sustained rise in pH. In two cases the aspirate remained alkaline
`
`

`
`145
`
`compound. The reduction in acid secretion was mediated
`primarily by a fall in acid concentration as no consistent altera-
`tion in the volume of the aspirate was noted. It was a subjective
`impression that viscosity of the gastric mucus was increased
`after exposure to the analogue, and it is possible that the in-
`hibitory effect on acid production did not extend to the non-
`parietal component of gastric secretion.
`Although the 15 (S) 15-methyl-E2 methyl ester compound
`showed a similar effect on basal secretion its use in this context
`is limited by its recognized excitatory effect on smooth muscle,
`in particular that of the uterus. Even in the limited dose range
`explored some unpleasant gastrointestinal symptoms were
`reported, and for these reasons the compound was not examined
`further once the broad pattern of response had been established.
`The 15 (R) analogue, on the other hand, appeared free from side
`effects and its uterine actions by the oral route are also known
`to be less marked.
`The failure of the parent E2 compound to inhibit basal acid
`secretion is probably due to its rapid metabolism and inactiva-
`tion. The 15-methyl derivatives are some 100 to 500 times more
`active and their duration of action on the uterus is longer by a
`factor of 3 to 4 when compared with the parent prostaglandin
`(Karim and Sharma, 1972; Karim et al., 1972 a). When given in
`high doses by intravenous infusion PGE, has been reported as
`having an inhibitory effect on acid production but only at the
`expense of an appr&iable incidence of undesirable sequelae
`(Wada and Ishizawa, 1970). It is therefore highly unlikely that
`PGE2 will ever enjoy a therapeutic role in the suppression of
`acid secretion.
`It has been suggested that the inhibition of gastric secretion
`by prostaglandins is due to a reduction in mucosal blood flow.
`While it is accepted that both the A and E series of compounds
`have a peripheral vasodilatory action the doses used in the
`present study had no effect on the blood pressure recorded by
`brachial artery cannulation (Karim et al., 1972 b). In addition
`Jacobson (1970), working with dogs, showed that the inhibitory
`effect of PGE1 was not due to a primary action on mucosal blood
`flow. While inhibition may result from changes in cyclic AMP
`concentrations it is also possible that there may be a direct
`action on the parietal cell. This last mechanism is supported
`by the observations that other prostaglandin fractions are
`capable of suppressing the secretion induced by histamine,
`pentagastrin, and vagal excitation (Ramwell and Shaw, 1968;
`Robert et al., 1968 a; Main, 1969; Wilson et al., 1971). These
`mechanisms of inducing acid secretion are currently being
`challenged in our laboratory by the 15 (R) 15-methyl-E.
`methyl ester and the results will be published in detail
`separately. Our preliminary experience is that the compound
`is very effective in the reduction of pentagastrin-induced acid
`secretion.
`The main interest in the present report lies in the fact that
`for the first time an oral preparation of prostaglandin has been
`shown to inhibit acid production. Of the two synthetic analo-
`gues the 15 (R) isomer shows the greater promise in that the
`effect is apparently free from side effects. The oral route of
`administration has obvious advantages if the analogue is to have
`therapeutic application to the problem of peptic ulceration, and
`we have had similar results after giving the dose in a hard gelatin
`capsule. The vehicle of 10 ml of water described here was used
`to ensure adequate contact with the secretory mucosa although
`it is possible that the contact time of 30 minutes does not allow
`complete absorption. In this context we have not attempted to
`measure the amount of prostaglandin returning with the aspirate,
`and it is possible that the doses used may give an artificially high
`impression of the. amount of prostaglandin producing the
`observed effect.
`In experimental animals Robert et al. (1968 b, 1971) showed
`the ulcer-sparing effect of PGE1 in experimentally induced
`gastric and duodenal ulceration in short-term experiments. It is
`conceivable that the 15 (R) analogue used in our studies could
`produce a similar beneficial effect in the human peptic ulcer
`situation. If the compound is to be assessed in this context it is
`
`20 JANUARY 1973
`BRITISH MEDICAL JOURNAL
`6 PG 15(R) 15-me-E2meEster
`
`I
`
`r-
`.P
`
`a0
`
`9E
`
`0-
`
`:2
`
`2
`
`0
`
`FIG. 4-Effect of oral dose of 200 gig prostaglandin 15 (R) 15-methyl-E2
`methyl ester on basal acid secretion.
`
`PG 15(S)15-me-E2me Ester
`
`25,uq
`o-o 50,ug
`
`3
`
`a-
`
`E
`
`0
`
`2
`Time (hr)
`FIG. 5-Effect of 25 and 50 iLg of orally administered prostaglandin 15 (S)
`15-methyl-E2 methyl ester on basal acid secretion.
`
`0
`Basal
`
`3
`
`4
`
`aLkaline in one case for 45 minutes the pH in the other subject
`did not rise above 4. As with the 15 (R) compound the varia-
`tions in output resulted from a fall in acidity rather than
`volume.
`Dose 50 jg (2 tests).-Complete inhibition of acid secretion
`occurred in both of these tests and was sustained for 90 minutes
`5). Once more little or no fluctuation in volume was
`(fig.
`observed and the pH rose in both instances to remain higher
`than 7 for at least 90 minutes.
`Comparative control data were available for all four tests
`performed with the 15 (S) analogue (see table). No adverse
`side effects were reported after 25 i&g, but after 50 Fg one of the
`subjects complained of nausea, and borborygmi were apparent
`during the procedure.
`
`Discussion
`The inhibition observed in response to oral administration of
`prostaglandin 15 (R) 15-methyl-E, methyl ester was both
`striking and sustained after 200 iLg, although a less marked
`inhibitory effect was also apparent after 100 and 150 Fg of this
`
`

`
`146
`
`inhibition extends
`important to ascertain whether the
`pepsin secretion, and this aspect is currently under review.
`
`to
`
`We wish to thank Professor S. K. Kyalwazi for his support and
`encouragement, and Mr. E. Zirimabagabo for technical help. The
`prostaglandins used in this study were either synthesized by Dr.
`W. P. Schneider in our laboratory or supplied by the Upjohn
`Company of Canada. We gratefully acknowledge the financial
`support of the Upjohn Company, Kalamazoo, Michigan, U.S.A.
`During the performance of this work D. C. C. was on secondment
`from the Department of Clinical Surgery, Edinburgh.
`
`References
`Bundy, G., Lincoln, F., Nelson, N., Pike, J., and Schneider, W. (1971).
`Annals of New York Academy of Sciences, 180, 76.
`Classen, M., Koch, H., Deyhle, P., Weidenhiller, S., and Demling, L.
`(1970). Klinische Wochenschrift, 48, 867.
`Horton, E. W., Main, I. H. M., Thompson, C. J., and Wright, P. M. (1968).
`Gut, 9, 655.
`
`BRITISH MEDICAL JOURNAL
`
`20 JANUARY 1973
`
`Jacobson, E. D. (1970). Proceedings of the Society for Experimental Biology
`and Medicine, 133, 516.
`Karim, S. M. M. (1971). Journal of Obstetrics and Gynaecology of the British
`Commonwealth, 78, 289.
`Karim, S. M. M., and Sharma, S. D. (1972). Journal of Obstetrics and
`Gynaecology of the British Commonwealth, 79, 737.
`Karim, S. M. M., Sharma, S. D., and Filshie, G. M. (1972 a). Proceedings
`of Brook Lodge Symposium on Prostaglandins.
`Karim, S. M. M., Somers, K., and Adaikan, Ganesan P. (1972 b). In pre-
`paration.
`Kirton, K. T., and Forbes, A. D. (1972). Prostaglandin, 1, 319.
`Main, I. H. M. (1969). British Journal of Pharmacology, 36, 214P.
`Ramwell, P., and Shaw, J. E. (1968). Journal of Physiology, 195, 34P.
`Robert, A., Phillips, J. P., and Nezamis, J. E. (1968 a). Gastroenterology,
`54, 1263.
`Robert, A., Nezamis, J. E., and Phillips, J. P. (1968 b). Gastroenterology,
`55, 481.
`Robert, A., Stowe, D. F., and Nezamis, J. E. (1971). Scandinavian Journal of
`Gastroenterology, 6, 303.
`Wada, T., and Ishizawa, M. (1970). Japanese Journal of Clinical Medicine,
`28, 2465.
`Way, L., and Durbin, R. P. (1969). Nature, 221, 874.
`Wilson, D. E., Phillips, C., and Levine, R. A. (1971). Gastroenterology,
`61, 201.
`Yankee, E. W., and Bundy, G. L. (1972). Journal of the American Chemical
`Society, 94, 3651.
`
`Multiple Renal Silica Calculi
`
`A. M. JOEKES, G. ALAN ROSE, JUNE SUTOR
`
`British Medical Journal, 1973, 1, 146-147
`
`Summary
`Investigation of a patient with a history of renal colic,
`who had taken the equivalent of 2 g magnesium trisilicate
`after every meal for many years, showed that he was
`forming silica calculi. The nature of the stone was
`diagnosed only after quantitative analysis.
`
`Introduction
`Silica stone was first described by Herman and Goldberg (1960)
`in the U.S.A. and was attributed to the ingestion of magnesium
`trisilicate for treatment of oesophagitis. Five more cases, also
`in the U.S.A., were reported by Lagergren (1962). Few cases
`have been described since then, and none in this country.
`Herring (1962) did not report any in his survey of 10,000 urinary
`calculi analysed by crystallographic and x-ray diffraction
`techniques. It was therefore thought appropriate to report a
`case of recurrent silica stones in this country.
`
`Case Report
`A 68-year-old man was first seen in November 1971 with a history of
`two episodes of presumed renal colic in 1940 with no precise diagnosis
`made at the time. After a fall in 1966 he developed a severe left-sided
`renal colic and radiography showed a large stone in the lower end of
`the left ureter with a much smaller stone immediately below it.
`Shortly afterwards a small stone weighing 100 mg was passed. At the
`beginning of 1969 he started having a series of renal colics affecting
`both the left and the right side. In June a stone was apparently removed
`from a diverticulum in the bladder. Some months later a small stone
`about 4 mm long was passed. This was slightly yellowish and very
`hard. He was free of any further colic until the beginning of 1971,
`
`St. Peter's Hospitals and Institute of Urology, University College,
`London WC2H 9AE
`A. M. JOEKES, B.M., F.R.C.P., Nephrologist
`G. ALAN ROSE, M.R.C.P., M.R.C.PATH., Consultant Chemnical Pathologist
`JUNE SUTOR, M.SC., PH.D., Research Fellow
`
`when he passed two small stones. He again passed a small stone after
`a renal colic in September 1971. On no occasion was the passage of
`stones accompanied by macroscopic haematuria.
`On examination he was an active, well-preserved man. Blood
`pressure was 190/90 mm Hg lying and standing. There was a healthy,
`rather wide, left paramedian scar. No other significant abnormal
`physical signs were found.
`Investigations were: haemoglobin 12 7 g/100 ml, white cell count
`7,000/mm3, packed cell volume 41%, E.S.R. 25 mm in 1 hr, plasma
`urea 46 mg/100 ml, creatinine 1 1 mg/100 ml, sodium 140 mEq/l.,
`potassium 4 0 mEq/l., bicarbonate 26 mEq/l., total protein 7-6 g/100
`ml, calcium 9-6 mg/100 ml, phosphate 2-4 mg/100 ml, uric acid 8-1
`mg/100 ml, 24-hour creatinine clearance 75 ml/min, 24-hour calcium
`excretion 85 and 84 mg, 24-hour urinary uric acid excretion 370 and
`360 mg.
`An intravenous pyelogram showed that the kidneys concentrated
`well and that the upper urinary tract was normal. There was a 1-cm
`low density calculus in the pelvic portion of the left lower ureter.
`The bladder was slightly trabeculated with a moderate residue after
`micturition.
`A radioactive renogram with 20 ,uCi of 1311 Hippuran and a urine
`flow rate of 4 ml/min showed a normal curve for the right kidney
`with no excretory abnormality. The left kidney showed considerably
`less good function with evidence of an obstructive lesion with a very
`slow excretory phase.
`The day after the intravenous pyeolography the patient had a
`severe suprapubic pain eventually radiating to the left flank. This
`continued for two days and he then passed the calculus that we had
`seen in the pelvic portion of the left ureter.
`
`STONE ANALYSIS
`Quantitative stone analysis was carried out by using the system of
`Westbury and Omenogor (1970), but as extended by Westbury (1972)
`to include oxalate determination. In addition, the usual qualitative
`tests were performed (see table). It was also noted that the powdered
`material was insoluble in dilute HCI but was soluble in dilute NaOH,
`and could be precipitated from this solution on acidification with
`HCI, and that the fresh precipitate was soluble in further excess HC1.
`These reactions are those of silica, the presence of which was therefore
`suspected. The confirmation of this suspicion was sought by x-ray
`crystallography. Silica occurs in calculi in the opaline state which is
`non-crystalline, but on heating it can be transformed into various
`crystalline forms depending on the temperature of ignition. The x-ray
`powder diffraction method was therefore used to determine if any
`crystalline material was present in the stone. Small samples from