Vpyl.=volume passing pylorus and Vabs.= volume absorbed. The volume. sulphaguanidine. This substance has been shown (Hunt, 1947) only to be

Transcription

1 134 J Physiol. (1949) I09, I34-I4I 6I :6I2.0I4.46I THE SIMULTANEOUS ESTIMATION OF THE ABSORPTION OF WATER AND SULPHAGUANIDINE FROM THE STOMACH OF MAN BY J. N. HUNT From Guy's Hospital Medical School, London (Received 7 October 1948) The absorption of water from the stomach of man has been established by the observations of Penner, Hollander & Post (1940). However, no estimates of the volume absorbed appear to have been made in man, although Sleeth & Van Liere (1937) have made measurements in anaesthetized cats. These authors showed that a mean of about 6-5 % of 200 ml. of water instil,ed into the stomach was absorbed in 3 hr. Since the rate of absorption was not influenced by the death of the animal, the process is presumably passive. There is support for this view in the work of Bandes, Hollander & Glickstein (1940) who showed that water was not absorbed when the gastric contents of dogs were isosmotic with plasma. This paper describes experiments in which the absorption of water from the stomach of man has been estimated simultaneously with the absorption of sulphaguanidine. This substance has been shown (Hunt, 1947) only to be absorbed when the osmotic pressure of the gastric contents is less than that of plasma. Thus, since the absorption of water and sulphaguanidine are both influenced by osmotic pressure, it appeared possible that their absorption might be related. If this were so an estimate of the absorption of water might perhaps be made from a measurement of the absorption of sulphaguanidine which is technically the simpler measurement to make. THEORETICAL CONSIDERATIONS The plan of the experiment. If fluid is introduced into a stomach, and subsequently recovered, the following simple relationship holds: Vrec. = Vj1. + Vsec. - Vpy1. - Vabs., (I) where Vre,. = volume recovered, V111 = volume ingested, Vec. = volume secreted, Vpyl.=volume passing pylorus and Vabs.= volume absorbed. The volume recovered and the volume ingested are known values. To find the volume absorbed, it is necessary to estimate the volume of secretion and the volume passing through the pylorus.

2 MEASUREMENT OF GASTRIC ABSORPTION 135 The calculation of the volume of gastric secretion from the amounts of Cl- and acid secreted. It appeared possible that the volume of gastric secretion might be calculated from the amounts of Cl- and acid secreted by the stomach. lhre (1938) made a detailed study of the gastric secretion of man in twenty-four normal subjects, stimulating secretion first with histamine and then with insulin. In his results he gave the concentrations of Cl- and acid and the volume secreted/hr. for each of these stimuli. Using Ihre's values the amounts, expressed in milli-equivalents, of Cl- and acid associated with each volume of juice have been calculated. The difference between the amount of C1- and acid contained in each measured volume of juice has been found, and this has been taken as the amount of so-called neutral C1-, i.e. C1 not in electrical equilibrium with hydrogen ions. From these values a regression plane of volume of gastric juice (dependent variable) on amounts of acid and neutral chloride has been calculated by the method of least squares to pass through the origin. This gives an equation V = 5-798H + 7*448N, where V = vol. of juice in ml., H = amount of acid in m.equiv., N =amount of neutral chloride in m.equiv. The mean difference between the volume of juice actually recovered by Ihre from the stomach and the volume calculated from the amounts of acid and C1- recovered is 3-15 ml. irrespective of sign, with a standard error of an individual difference ml. Equation II has been used to calculate the volume of gastric secretion responsible for the amounts of C1- and acid secreted by the stomach during the experiments reported in this paper. The calculation of the volume of gastric contents passing through the pylorus. Since the volume passing through the pylorus could not be measured directly, it was calculated in the following way. Phenol red was incorporated in the test solution ingested. This dye has been shown by Penner, Hollander & Saltzman (1938), Shay, Gershon-Cohen & Fels (1939) and Hunt (1947) not to be absorbed, adsorbed or secreted- by the gastric mucosa. The difference between the amount of phenol red ingested and the amount later recovered from the stomach was taken to be the amount of phenol red which had passed through the pylorus. Assuming a reasonably steady rate of change in the concentration of phenol red in the gastric contents due to dilution by secretion, the mean concentration of the phenol red in the gastric contents was taken to be half the sum of the concentrations at the beginning and at the end of the experiment. The amount of phenol red lost through the pylorus divided by the mean concentration at which it was lost gave a volume which was taken as the volume of gastric contents passing through the pylorus during the 'experimental period. Using this volume, and the mean concentrations of chloride and acid, allowances have been made for the amounts of these constituents passing out of the stomach through the pylorus. (II)

3 136 J. N. HUNT Practical application of equation I. Let us reconsider the original simple relationship Vrec. = Vjn. + Vsec. - Vpyl. -Vabs. (I) For anatomical reasons it is difficult to empty the stomach completely. Thus from a practical standpoint equation I should be rewritten: Vrec. = Vin. + Vsec. + Vrem.L - Vpyl. - Vabs. - Vrem2X (III) where Vrem.i =volume remaining in the stomach immediately before the ingestion of the test solution, Vrem2 =volume remaining in the stomach after aspirating the gastric contents. cannot be measured directly. Vremi, and ViIm2 but allowances can be made for them in the following way. Vrem.1. This fluid would consist of so-called 'resting juice', a mixture of saliva, gastric secretion and possibly bile, and would represent an error of unknown and varying degree in the ingested meal. To eliminate this variable error, the stomach has been washed out before each meal with saline of a concentration equivalent to that of neutral gastric juice. This procedure permits of the calculation of (Vse + Vrem.), without their separate evaluation, from the amounts of Cl- and acid recovered. The strength of NaCl solution required for this preliminary washout can be determined from the following consideration of equation II: V=5*798H+7-448N. (II) If H=O, i.e. the gastric juice is neutral, V= 7'448N. If V= 1 ml. N= m.equiv. neutral Cl-. contains m.equiv. NaCl, the use of equatiqn II Thus, if each ml. of Vrem, will ensure that any value of (V.ec. + Vrem.1) will be correctly computed from the amounts of C1- and acid recovered plus the amounts calculated to have been lost through the pylorus. In other words, equation II is true not only of gastric juice but also of mixtures of gastric juice and a saline containing 134 m.equiv. Cl-/l. Vrem.12 After withdrawing the gastric contents, the stomach is immediately washed out with water, the phenol red content of this wash determined and its equivalent volume of gastric contents calculated. In this way the difficulty of emptying the stomach completely before and after the experiment began has been overcome. It is thus possible to estimate Vab. since it is the only unknown in equation III. In order that the volume available for absorption from the stomach should be kept as large as possible, use has been made of the effect of the intra-duodenal instillation of olive oil in delaying gastric emptying (Shay et al. 1939).

4 MEASUREMENT OF GASTRIC ABSORPTION 137 METHODS The following technique has been used to intubate the duodenum. The subject was given 2 m. of stiff rubber tubing 3 mm. in external diameter, and having several perforations a few cm. from one end. He swallowed about 1 m. of tube before his evening meal and a further 50 cm. during the subsequent hours. During the night the upper end was pinned on to his pyjamas whilst the lower perforated end was swept through the pylorus with his supper. On the following morning he came to the laboratory without breakfast and swallowed a soft rubber tube, 2 mm. external diameter. The subject sat in a chair, continuous aspiration of saliva from the mouth was begun and about 30 drops/min. of olive oil were then run continuously into the stiff rubber tube which was withdrawn until it was thought to be in the duodenum. After 10 min. the subject drank 400 ml. of a solution of NaCl (130 m.equiv./1.). (A later calculation gave 134 m.equiv./i.: the error is considered to be insignificant in this context.) As much as possible of this solution was drawn out through the soft tube at once. If no oil was recovered with this saline, ml. of a solution containing about 100 mg. of phenol red/l. and about 100 mg. sulphaguanidine/l. at a ph 6-5.were run into the stomach through the soft tube during a period of 5-8 min. This solution has a depression of freezing-point of about In five experiments 0 5 mg. histamine acid phosphate was then injected subcutaneously. One hour later the gastric contents, which were never contaminated with oil, were recovered through the soft rubber tube and their volume measured. The subject then drank 200 ml. of water which were recovered through the soft tube and the volume measured. This washout was then repeated. The concentrations of sulphaguanidine and phenol red in the original test solution and in the recovered gastric contents and washout solutions were determined by methods previously described (Hunt, 1947). The concentration of acid was determined in the sample first recovered by titrating to a ph of 6-5 determined electro-potentiometrically. Since the isoelectric point of one group of the buffers present in gastric juice is ph 6-5 (Hori, 1933) the titration is as far as possible independent of the concentrations of these substances if it is assumed that they are secreted at their isoelectric point. In any case the probable magnitude of the error from this source is small. The concentration of C1- ions was-then determined by titrating with 0-5N-silver nitrate in the presence of small amounts of nitric acid until the e.m.f. measured between a calomel half cell and a silver/silver chloride electrode showed a maximal rate of change/unit of silver nitrate added. Mathematical treatmenr of the results The percentages of Table 1 are expressed as mg. in the following calculation. Correction for incomplete emptying of stomach Concentration of phenol red in first recovery = 83-4 mg./l. Concentration of phenol red in first washout = 10.0 mg./l. Recovered volume of first washout = Amount of phenol red in recovered volume of first washout =0 190 x 10 mg. Volume of first recovery fluid equivalent to amount of phenol red in recovered washout (Vrm) = x 10 =23 ml. The second washout contained a negligible amount of phenol red. estimate Vrem.2 with some precision. Correction for gastric contents lost through the pylorus Volume of ingested fluid containing phenol red and sulphaguanidine =0-1. Concentration of phenol red in ingested solution = 100 mg./l. Amount of phenol red ingested=0- x 100 mg. Vrec. + Vrem.2 (see Table 1) = Concentration of phenol red in the sample first recovered= 83-4 mg./l. Amount of phenol red recovered =0-515 x 83*4 mg. In this way it was possible to

5 138 J. N. HUNT Amount of phenol red passing pylorus = amount ingested - amount recovered =0 x x 83-4 mg. Mean concentration of phenol red in gastric contents passing through the pylorus during the hour= = mg./l Volume of gastric contents passing through the pylorus Amount of phenol red lost through pylorus Mean concentration of phenol red in gastric contents 0- x x *7 = Thus of gastric contents passed through the pylorus. Calculation of volume ab8orbed By rearranging equation III, Vabs. = Vin. + ( V8ec. + Vreml) - VPYL - ( Vrm2 + Vre.)' (IV) On the right side of the equation the only unknown is (Vec. + Vrem.1). The calculation of (Ve, + Vrw,3l) from the calculated recovery of chloride and acid Concentration of chloride in first recovery=29*14 m.equiv./l. Amount of chloride recovered =29-14 x m.equiv. 29*14 Mean concentration of chloride in the passing through the pylorus= 2 m.equiv./l x0-349 Amount of chloride passing through pylorus = 2 m.equiv. Total amount of chloride = amount recovered + amount lost through the pylorus = m.equiv. Similarly, the total amount of acid secreted may be calculated to be m.equiv. From equation II it was found that this amount of Cl- and acid corresponded to 131 ml. of gastric secretion, i.e. V,,e. + Vm = 131. Substituting numerical values in equation IV Va,. = , therefore water absorbed = 17 ml., i.e. 2 7 % of the mean volume of the gastric contents. Calculation of the amount of 8ulphaguanidine absorbed Volume of test meal and secretion passing pylorus = (see above). Mean concentration of sulphaguanidine passing pylorus = mg./l. Amount of sulphaguanidine lost through pylorus-349 x g Amount absorbed =amount ingested - amount recovered - amount passing pylorus x -=0 x x mg. g = 1-63 mg. of sulphaguanidine. Mean amount of sulphaguanidine in stomach ( x ( ) =57 27 mg x100 Absorption of sulphaguanidine= %. Absorption of water (see above) =2-7 %. mg.

6 MEASUREMENT OF GASTRIC ABSORPTION 139 RESULTS Nine experiments on eight healthy students progressed as far as the successful withdrawal and washout of the gastric contents; the results are given in Table 1. One other experiment during which the subject complained of nausea was discarded as the gastric contents were stained with bile. The mean calculated absorption of water was 9-3 ml./hr. S.E. of mean ml. Expressed as a percentage of the mean volume of the gastric contents, a mean of 1-48 %, S.E. mean % was absorbed. Calculated by the use of 'Student's' ' t' test, the chance that this value would be found if there was in fact no water absorption is 1 in 20. The mean calculated absorption of sulphaguanidine expressed as a percentage of the mean amount of sulphaguanidine in the stomach was 1-41 %, S.E. mean + 060%. If there were no absorption of sulphaguanidine such a value might also be expected to arise once out of twenty times by chance. Thus considering the experiments as a group it appears that the absorption of water and sulphaguanidine are of the same order and are statistically significantly different from zero. However, when the values for each subject are considered separately, it is evident that no correlation between the absorption of sulphaguanidine and water has been demonstrated for individuals. TABLE 1. Subject Volume ingested (ml.) Volume recovered (ml.) The absorption of water and sulphaguanidine from the stomach of man No histamine 0 5 mg. histamine phosphate A A,r A... Vorc + Vrm,- Conc. phenol red recovered as % of cone. ingested Conc. sulphaguanidine recovered as % of conc. ingested Conc. C1- m.equiv./l. in recovered gastric content Cone. acid m.equiv./l. in recovered gastric content Volume gastric content passing through pylorus Volume secreted calculated from amounts of C1- and acid secreted (ml.) (Vse. + vrmld Water absorbed (ml.) Water absorbed expressed as % of mean vol. gastric contents Sulphaguanidine absorbed expressed as % of mean amount in the stomach -4 E. # Eq 530 E4 705 v Ez * * *5 86* * * Nil *17 Nil * * * * 't *7

7 140 J. N. HUNT DISCUSSION Let us consider the sources of error in the calculations given for subject W.V.J. (1) The calculation of the volume of secretion from the amounts of Cl- and acid secreted has a mean error of ml. and S.D. of an individual difference ml. (2) The sum of the standard errors of estimations of the concentrations of phenol red and sulphaguanidine have been shown to be / (Hunt, 1947). If an error is made in the estimation of sulphaguanidine such that the true concentration is 82-1 mg./l. instead of 81.1mg./l., the absorption of sulphaguanidine may be calculated to be 0 95 mg. This is 1-6% of the mean amount of sulphaguanidine in the stomach instead of 2-8 % calculated from the results of the experiment. Thus an error of about 1% in the estimation of the concentration of sulphaguanidine would in this case reduce the calculated absorption of sulphaguanidine by one-third. (3) The assumption is implicit throughout that mixing in the stomach is complete. Although the sum of these errors is probably random about zero for a group of subjects, it was apparent that a considerable improvement in technique would be necessary to demonstrate any correlation between the absorption of water and sulphaguanidine in an individual. It was thought possible that the low rates of secretion seen in the first three experiments might be associated with a low gastric blood flow and that this might be a factor in reducing the absorption of water. For this reason a further five experiments were made with the addition of a subcutaneous injection of histamine. Whilst this was effective in causing an increase in the rate of secretion there was no apparent effect on the absorption of water. It is perhaps worthy of note that subject R.C.B.D., who showed minimal absorption of water, had on two previous occasions been shown not to absorb sulphaguanidine when this was measured without the concurrent absorption of water being estimated. This accords with the experience of Wilhelmj, Finegan & Hill (1937) who found that individual dogs were consistent in their absorption or non-absorption of water. Thus, under the conditions of these experiments, water absorption of about 1-5 %/hr. appears to have taken place. This agrees well with the 6-5 %/3 hr. i.e. 2-2 %/hr., found by Sleeth & Van Liere (1937) in cats, especially if the relatively smaller surface area presented by the larger volume contained in the stomach of man is borne in mind. The conditions of these experiments are unlike those existing in an actively motile digesting stomach, so that the results do not warrant the uncritical acceptance of the assumption that the stomach of man never absorbs significant quantities of water. Penner et al. (1940), who noted significant absorption of water, used much smaller volumes than were given in the present research. Corresponding to their findings, when smaller volumes of fluid were retained in

8 MEASUREMENT OF GASTRIC ABSORPTION 141 the stomach during an earlier investigation of the absorption of sulphaguanidine (Hunt, 1947) it was found that up to 12% of the calculated mean total amount of sulphaguanidine in the stomach was absorbed. The olive oil instilled into the duodenum had a most remarkable delaying effect on gastric evacuation. Shay et al. (1939) found that olive oil instilled into the duodenum caused the stomach completely to retain 200 ml. of fluid for 30 min. It is, nevertheless, rather surprising that the same method should be so successful in inhibiting for 1 hr. the emptying of a stomach containing up to four times this volume. SUMMARY 1. A technique is described for estimating the water and sulphaguanidine absorbed by the stomach. 2. In nine experiments on eight healthy human subjects the mean absorption of water was 15 %/hr. of the mean volume of water in the stomach. The absorption of sulphaguanidine was 1.4%/hr. of the mean amount of sulphaguanidine in the stomach. These values are statistically significantly different from zero. 3. Olive oil instilled into the duodenum was in every case very effective in slowing the emptying of the stomach containing more than 500 ml. of test solution. My thanks are due to the students who enthusiastically took part in these experiments. I am greatly indebted to Dr R. B. Fisher for advice and help with the statistical calculations and to Prof. W. R. Spurrell for encouragement and many helpful suggestions in the preparation of the manuscript. REFERENCES Bandes, J., Hollander, F. & Glickstein, J. (1940). Amer. J. Physiol. i13, 470. Hori, M. (1933). Jap. J. Gastroent. 5, 13. Hunt, J. N. (1947). GUy'8 Hosp. Rep. 96, 248. lhre, B. (1938). Acta med. scand. Suppl. no. 95. Penner, A., Hollander, F. & Post, A. (1940). Amer. J. digest. Dis. 7, 202. Penner, A., Hollander, F. & Saltzman, M. (1938). Amer. J. digest. Di8. 5, 657. Shay, H., Gershon-Cohen, J. & Fels, S. S. (1939). Amer. J. digest. Di8. 6, 361. Sleeth, C. K. & Van Liere, E. J. (1937). Proc. Soc. exp. Biol., N.Y., 36, 571. Wilhelmj, C. M., Finegan, R. W. & Hill, F. C. (1937). Amer. J. digest. Dis. 4, 547.