COMPARATIVE EFFECTS OF GASTRIN II AND HISTAMINE ON PEPSIN SECRETION IN MAN

GASTROENTEROLOGY COpyright 1967 by The Williams & Wilkins Co. Vol. 52, No.5 Printed in U.S.A. COMPARATIVE EFFECTS OF GASTRIN II AND ISTAMINE ON PEPSIN SECRETION IN MAN G. M. MAKLOUF, M.B., PD., M.R.C.P., M.R.C.P. (ED.), J. P. A McMANUS, M.B., M.R.C.P. (ED.), AND W. 1. CARD, M.D., F.R.C.P., F.R.C.P. (ED.) Gastrointestinal Unit, Western General ospital, Edinburgh, and the University of Edinburgh, Edinburgh, Scotland In an earlier study, the effects of histamine and the penta peptide derivative of gastrin on the secretion of pepsin and total nitrogen in man were found to be substantially similar.1 In the present study the effects of gastrin II and histamine on the same constituents are investigated and the data obtained from man are compared with those obtained from whole stomachs in conscious dogs and cats. 2 Procedure and Methods Seven subjects (3 with duodenal ulcer, 2 with gastric ulcer, and 2 normal) were each tested on separate occasions with 4 /Lg per kg of histamine acid phosphate or 1 /Lg per kg of gastrin II administered subcutaneously. The choice of the gastrin dose was dictated by the need to obtain equivalent levels of acid secretion from the two stimulants: The procedures for the collection of secretion and avoidance of salivary contamination have been described in earlier communications.'-" Two 2-min samples of spontaneous secretion (basal) were collected prior to each test. Stimulated secretion was collected every 5 min for 8 min. Eight lo-min samples were obtained for analysis in each case. The following estimations were made: ion concentra- Received December 12, 1966. Accepted January 11, 1967. Address requests for reprints to: Dr. G. M. Makhlouf, Lemuel Shattuck ospital, 17 Morton Street, Boston, Massachusetts 213. This work was supported by a grant from the Medical Research Council, Great Britain, and by Research Grant AM-1377 from the National Institutes of ealth, United States Public ealth Service. The authors wish to express their gratitude to Professor R. A. Gregory for his gift of gastrin II, and to Miss Irene Newlands for technical assistance. tion by titration to the phenolphthalein end 787 point, pepsin by the method of unt, and biuret-reacting nitrogen by a modification of the method of Gornall et al.' Results Volume and acid output. Following both gastrin and histamine, peak volume and acid outputs occurred simultaneously during the third and fourth lo-min periods (fig. 1). The mean volume and acid outputs during the hour following stimulation were similar for the two stimulants. Output oj pepsin and nitrogen. The pattern of pepsin secretion was somewhat different from that of acid. Following both gastrin and histamine, the output of pepsin rose to an early peak in the second 1- min period but declined more rapidly with histamine (fig. 1). In each subject both peak output and the output during the hour following stimulation were noticeably higher after histamine than after gastrin (P <.2 by the Wilcoxon matched-pairs signed-rank tests) (table 1). The mean increase in pepsin output was 4-fold after histamine and 3-fold after gastrin. The output pattern of nitrogen followed that of pepsin (fig. 1). ere again the output after histamine was, in all subjects but one, higher than the output after gastrin (P <.4) (table 1). The mean increase in nitrogen output was 3-fold after histamine and 2-fold after gastrin. Concentration. The concentration levels are portrayed in figure 2. Following a short-lived initial rise, the concentration of pepsin fell rapidly with gastrin but more slowly with histamine to a level equivalent to half the basal concentration level. The concentration of nitrogen fell or rose approximately inversely to that of acid. Comparison and correlation oj the out-

788 MAKLOUF ET AL. Vol. 52, No.5 puts oj acid, pepsin, and nitrogen. Table 1 is a record of the outputs of acid, pepsin, and nitrogen in increasing order of magni- 1 c: 8 'e Q... IT.. 6 E 4 U <t 2 3 c: e Q 2....,. E N 1 z, /"x -,,:),x,! '\- G i ' / tude from left to right. Both the basal and stimulated outputs of acid and pepsin increased coincidentally, the larger outputs of acid being accompanied by correspondingly larger outputs of pepsin. -,12...... 8 + o 4 + ::c 6 z 8 4 : I- Z 2 8 eo 2 4 6 eo MINUTES FIG. 1. The mean outputs per 1 min of acid, pepsin, and nitrogen following stimulation by gastrin II (X ) and histamine ( ). 24 -'... :.: '" 16 Z iii 11. 8 11. }I.f,\- x x"'-- " '--- x-...x:::::""=i=i--' G eo 2 4 6 8 MINUTES FIG. 2. The mean concentration levels per 1 min of acid, pepsin, and nitrogen following stimulation by gastrin (X) and histamine (.). TABLE 1. The individual outputs of acid, pepsin, and nitrogen du1'ing the 1st hr following stimulation by gastrin II and histamine a Normal subjects Gastric ulcer patients Duodenal ulcer patients M.M. G.M. J. G. W.M. T.D. J.S. R.R. (F) (M) (F) (M) (M) (M) (M) ---- --- - - --- - ----- - -- Acid (meq/hr), gastrin-stimulated........,... 17.9 24.1 22. 45.1 45.2 6.24 77.5 Acid (meq/hr), histamine-stimulated.......... 2. 23.6 26.6 34. 45.4 54.4 83.6 Pepsin (kilounits/hr), gastrin-stimulated.... 15.7 17.2 2.6 36.2 35.3 43.1 61. 2 Pepsin (kilounits/hr) histamine-stimulated..... 24.3 22.9 25.7 43.9 48.3 5.6 11.3 Nitrogen (mg/hr), gastrin-stimulated.....'. 4.1 56.2 94.3 116.1 18.1 62.9 28.6 Nitrogen (mg/hr), histamine-stimulated... 59.7 52.8 114.6 141. 6 115.1 83.1 33.7 Acid (meq/hr), basal................. Pepsin (kilounits/hr), basal...... :\.5.9 2.2 2.9 5. 5.7 7.8......... 2.2 I 2.8 6.9 11.2 13.9 15.8 29.2 a The data are recorded in increasing order of magnitude from left to right.

May 1967 EFFECTS OF GASTRIN II AND ISTAMINE The following correlations were derived from the dat Basal secretion: Basal acid output was correlated with basal pepsin output (r =.97, P <.1), basal acid output with stimulated acid output (r =.98, P <.1), and basal pepsin output with stimulated pepsin output (r =.96, P <.1) (fig. 3). Stimulated secretion: The pepsin outputs, though on average some 3% lower after gastrin, were highly correlated with the corresponding pepsin outputs after histamine (r =.96, P <.1). The pepsin outputs on stimulation were also correlated with the corresponding acid outputs (for histamine, r =.97, P <.1; for gastrin, r =.99, P <.1) (fig. 4). As indicated by the slopes of the linear correlations in figure 4, the amount of pepsin secreted with each milliequivalent of acid was higher undeli basal conditions (3.3 kilounits) than after histamine (1.1 kilounits) or gastrin (.8 kilounits). The nitrogen outputs after gastrin were correlated with the corresponding outputs after histamine (r =.97, P <.1). The amount of nitrogen which accompanied the secretion of 1 meq of acid was also higher under basal conditions (13.3 mg) than after histamine (3.1 mg) or gastrin (2.3 mg). Discussion It is generally agreed that histamine stimulates the secretion of pepsin by the human stomach; continuous infusion of maximal 9 or half-maximal 1o doses of histamine results in a sustained increase in the output of pepsin. The nearly 4-fold increase in pepsin output over basal levels observed in this study following subcutaneous histamine is supported by a number of previous reports. 1-13 The significant difference between the outputs of pepsin and nitrogen after histamine and gastrin at a time when the volume flows from the two stimulants were similar should preclude an interpretation on the basis of a washout. The significant correlation between the acid and pepsin outputs similar to that found in an earlier studyl with histamine and the pentapeptide derivative of gastrin 3 "- " 2 <f) '"...J <: 1 <f) <: m 2 4 6 8 STIMULATED PEPSIN Ku/hr FIG. 3. Correlation between the basal and stimulated outputs of pepsin (r =.96, P <.1). For each subject the mean output of the two basal tests was plotted against the mean output of the histamine and gastrin tests. 1 8.c; -;; 6 z " iii :::; 4 o 2 6 8 ACID meq Ihr I I FIG. 4. Relationship between the outputs of acid and pepsin during basal secretion (.&.) (r =.97, P <.1), and following stimulation by gastrin (X) (r =.99, P <.1) and histamine (.) (r =.97, P <.1). suggests that the peptic and parietal cell masses are present in the same proportion in different individuals. The significant correlation between the basal and stimulated outputs for both acid and pepsin suggests that the main, though probably not the sole, determinant of basal output is the gastric cellular mass of the individual. The amount of pepsin which accompanied the secretion of one milliequivalent of acid was three to four times higher during spontaneous secretion. This observation bears some analogy to the findings

79 MA KLOUF ET AL. Vol. 52, N o. 5 in cats and dogs where the pepsin to acid ratio is highest in spontaneous secl'etion. 2 The parallel behavior of the pepsin and nitrogen outputs is further underlined by the fac t that the same amount of nitrogen accompanied the secretion of 1 kilounit of pepsin: 2.9 mg after histamine and 3. mg after gastrin. Although biuret-reacting nitrogen i s only a crude indicator of the combined activity of the peptic and mucous cellular masses, the parallelism in the behavior of pepsin and nitrogen suggests that the mucous cells share in the discrepancy of response to the two stimulants. On the other hand, the amount of intrinsic factor which accompanies the secretion of 1 meq of acid may be calculated from the data of Wangel and Callenderl4 and is similar for gastrin (.37 kilounits) and histamine (.39 kilounits) -appropriately s o perhaps, in view of the probable common cellular origin of these two constituents in man. l5 D espite the significant difference between the pepsin responses to histamine and gastrin at doses which elicit similar acid outputs, it cannot be firmly asserted that hist amine is the more potent pepsigogue. In an earlier studyl it was found that t he pepsin response to 6 p,g per kg sc of the pentapeptide derivative of gastrin was similar to that for histamine. The response showed, however, a tendency to dep/g 6 / s:.... 4 z in Q. 2 Q. o ' ACID meq Ihr FIG. 5. Relationship between the outputs of pepsin and acid during maximal or sub maximal stimulation of acid by gastrin (x) or histamine (. ). The gastrin and histamine s lopes a re similar to the corresponding slopes in figure 4. The symbols a and a' represent data on submaximal stimulation by histamine'7 and gastrin,' respectively. crease at the highest doses. Should a reversal of the pepsin response occur in man following large doses of gastrin II, then the 1 p,g per kg dose used in this study, while eliciting a near maximal secretion of acid, may have induced partial inhibition of the pepsin response. Conversely, the gastrin dose may have been insufficient to stimulate maximally the secretion of pepsin. Both these possibilities must be retained until dose-response curves for the effect of gastrin on pepsin secretion in man have been constructed. The evidence available to date, however, though indirect, suggests that the lower pepsin output after gastrin does not represent a diminution in response. If the mean pepsin outputs for gastrin obtained (a ) from the dat a of Johnston and Duthie,t6 who used a half-maximal infusion of gastrin II, and (b) from the present study with subcutaneous gastrin, are plotted aainst the corresponding mean acid outpu ts (fig. 5), they fall on a slope similar to the gastrin slope displayed in figure 4. Similarly, if the mean pepsin outputs for histamine obtained (a) from the data of unt,t7 who used a submaximal subcutaneous dose of histamine acid phosphate (1 p,g per kg), and (b) from the present and an earlier studyl with subcutaneous histamine, are plotted against the corresponding mean acid outputs, they fall on a slope similar to the histamine slope of figure 4. The recent report by Emits and Grossman 2 on the acid and pepsin responses to histamine and gastrin of conscious dogs and cats with gastric fistulae is of special significance in that it permits comparison with the data obtained in man. In both cat and dog, t he pepsin response to hist a mine reaches an early peak, with doses that are distinctly submaximal with respect to acid secretion; thereafter the response diminishes with progressive increases in the dose. In both animal species, the pepsin response to gastrin is much higher and appears to reach its maximum at doses which are also maximal with respect to acid secretion. Further increases in the dose of gastrin result in a measure of inhibition of acid and pepsin in the dog but not in the cat.

May 1967 EFFECTS OF GASTRIN II A N D ISTA MIN E 791 There appears to be no inhibition of the pepsin 9 1 output in response to large doses of histamine in man, while the data in this study show that, if anything, the pepsin response to gastrin is the lower of the two. In both these respects the pepsin response in man appears to differ from that in cats and dogs. As pointed out above, however, a more confident assertion of a true species difference must await the construction of dose-response curves for pepsin in man. Summary Seven subjects were tested with doses of gastrin II and histamine that elicited similar near-maximal outputs of acid. The outputs of pepsin after gastrin, though invariably lower, were significantly correlated with the corresponding outputs after histamine. The consistency ; of this effect was underlined by the significant correlation between the outputs of acid and pepsin for each stimulant. The parallel behavior of the outputs of nitrogen suggests that the discrepancy in response was also shared by the mucous cells. The contrast in the effect of the two stimulants on the secretion of pepsin in man and animals is discussed. REFERENCES 1. Makhlouf, G. M., J. P. A. McManus, and W. 1. Card. 1966. Action of t he pentapeptide (ICI 5123) on gastric secretion in man. Gastroenterology 51: 455-465. 2. E mas, S., and M. 1. Grossman. 1967. Comparison of gastric secretion in conscious dogs and cats. Gastroenterology 5 2 : 29-34. 3. Makhlouf, G. M., J. P. A. McManus, and W. 1. Card. 1964. The action of gastrin II on gastric acid secretion in man. Lancet 2: 485-49. 4. Makhlouf, G. M., J. P. A. McManus, and W. I. Card. 1964. Dose-response curves for the effect of gastrin II on acid gastric secretion in man. Gut 5: 379-384. 5. Makhlouf, G. M., J. P. A. McManus, and W. I. Card. 1965. A comparative study of the effects of gastrin, histamine, istalog and mechothane on the secretory capacity of the human stomach in two normal subjects over 2 months. Gut 6: 525-534. 6. unt, J. N. 1948. A m ethod for estimating peptic activity in gastric contents. Biochem. J. 42: 14-19. 7. Gornall, A. C., C. J. Bardawill, and M. M. David. 1949. Determination of serum proteins by means of biuret reaction. J. BioI. Chern. 177 : 751-766. 8. McCornack, R. L. 1965. Extended tables of the Wilcoxon matched-pair signed-rank statistic. Amer. Stat. Assn. J. 6: 864-871. 9. Wyllie, J.., nd a G. Smith. 1965. istamineinfusion test. Lancet 2: 823-824. 1. irschowitz, B. I. 1961. Electrolytes in human gastric secretion. Observations and a theory. Amer. J. Dig. Dis. (N.S.) 6: 199-228. 11. Piper, D. W. 196. The effect of histamine on pepsin secretion. Amer. J. Dig. Dis. (N.S.) 5 : 88-888. 12. Gillespie, I. E., and D. J. Bowen. 1962. The gastric secretion of pepsin in man. Gut 3: 255-259. 13. Ashford, C. A.,. eller, and G. A. Smart. 1949. The ac tion of histamine on hydrochloric acid and pepsin secretion in man. Brit. J. Pharmacol. 4: 132-136. 14. Wangel, A. G., and S. T. Callender. 1965. Effect of gastrin I and II on the secretion of intrinsic factor. Brit. Med. J. 1: 149-1411. 15. oedemaker, P. J. 1965. In Investigations on the site of production of Castle's gastric intrinsic factor, p. 25. Groningen. 16. Johnston, D., and. L. Duthie. 1965. Inhibition of gastric secretion in the human stomach. Effect of acid in the duodenum. Lancet 2: 132-136. 17. unt, J. N. 195. An interpretation of the histamine test of gastric secretion. Gastroenterology 16: 231-24.