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Effect of Peptide Histidine Isoleucine on Water and Electrolyte Transport in the Human Jejunum

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Effect of Peptide Histidine Isoleucine on Water and Electrolyte Transport in the Human Jejunum Gut: first published as 10.1136/gut.25.6.624 on 1 June 1984. Downloaded from Gut, 1984, 25, 624-628 Alimentary tract and pancreas Effect of peptide histidine isoleucine on water and electrolyte transport in the human jejunum K J MORIARTY, J E HEGARTY, K TATEMOTO, V MUTT, N D CHRISTOFIDES, S R BLOOM, AND J R WOOD From the Department of Gastroenterology, St Bartholomew's Hospital, London, The Liver Unit, King's College Hospital, London, Department ofMedicine, Hammersmith Hospital, London, and Department of Biochemistry, Karolinska Institute, Stockholm, Sweden SUMMARY Peptide histidine isoleucine, a 27 amino acid peptide with close amino acid sequence homology to vasoactive intestinal peptide and secretin, is distributed throughout the mammalian intestinal tract, where it has been localised to intramural neurones. An intestinal perfusion technique has been used to study the effect of intravenous peptide histidine isoleucine (44.5 pmol/kg/min) on water and electrolyte transport from a plasma like electrolyte solution in human jejunum in vivo. Peptide histidine isoleucine infusion produced peak plasma peptide histidine isoleucine concentrations in the range 2000-3000 pmolIl, flushing, tachycardia and a reduction in diastolic blood pressure. Peptide histidine isoleucine caused a significant inhibition of net absorption of water, sodium, potassium and bicarbonate and induced a net secretion of chloride, these changes being completely reversed during the post-peptide histidine isoleucine period. These findings suggest that endogenous peptide histidine isoleucine may participate in the neurohumoral regulation of water and electrolyte transport in the human jejunum. http://gut.bmj.com/ Peptide histidine isoleucine, isolated originally from INTESTINAL PERFUSION mammalian small intestine, is a 27-amino acid After an eight hour fast, each subject swallowed a peptide having close amino acid sequence homology double lumen intestinal perfusion tube, incorpo- to vasoactive intestinal peptide and secretin. ' rating a proximal occluding balloon, a 30 cm test Peptide histidine isoleucine-like immunoreactivity segment and a mercury bag.9 The tube was on September 27, 2021 by guest. Protected copyright. has recently been shown in intestinal intramural positioned under fluoroscopic control such that the neurones of the dog, pig and mouse4 and also balloon was situated at the ligament of Treitz with throughout the human gastrointestinal tract.5 The the infusion orifice located in the first 5 cm of inhibitory effect of peptide histidine isoleucine on jejunum. Using a peristaltic pump, a plasma like fluid absorption in pig and rat7 small intestine and electrolyte solution at 37°C was perfused through in guinea pig gall bladder8 has led us to investigate the infusion orifice at a rate of 15 ml/min. The its effect on water and electrolyte transport in the solution contained (mmol/l): Na, 135; K, 5; Cl, 110; human jejunum. HCO3, 30; polyethylene glycol (PEG), 2 5 g/l and 1,uCi/l of [14C]PEG as a non-absorbable marker. Methods The solution was continuously oxygenated throughout each experiment with 95% 02-5% CO2- SUBJECTS After a 30 minute equilibration period, during which Six healthy volunteers (three men, three women), the aspirates were discarded, serial 10 minute each aged 21 years, gave written informed consent aspirates were collected by siphonage. Aliquots for the study which was approved by the Ethical were taken for immediate bicarbonate estimation Committee of King's College Hospital, London. and samples for determination of other electrolyte concentrations were stored at -20°C before analysis. Address for correspondence: Dr K J Moriarty. Department of Gastro- cnterology. St Bartholomew's Hospital. West Smithfield. London ECIA 7BE. COURSE OF PERFUSION EXPERIMENTS Received for publication 27 September 1983 Natural porcine peptide histidine isoleucine 624 Gut: first published as 10.1136/gut.25.6.624 on 1 June 1984. Downloaded from Effect ofpeptide histidine isoleucine on water and electrolyte transport in the human jejunum 625 (Gastrointestinal Hormone Laboratory, Karolinska Results Institute, Stockholm)3 was dissolved in sterile isotonic sodium chloride containing 0-5% human PLASMA PEPTIDE HISTIDINE ISOLEUCINE serum albumin immediately before use in order to CONCENTRATIONS minimise peptide degradation and adherence to the Plasma peptide histidine isoleucine concentrations glass and plastic used in its preparation and intra- rose from 20-110 pmol/l in the pre-peptide histidine venous administration. The peptide used was highly isoleucine period to 2000-3000 pmol/l during purified, containing only trace amounts (<1%) of peptide histidine isoleucine infusion (Figure). porcine secretin. Peptide histidine isoleucine was Thereafter, plasma peptide histidine isoleucine infused into a peripheral vein in the left arm of each concentrations decreased, returning to pre-peptide subject at a rate of 44*5 pmol/kg/min during the histidine isoleucine levels 60 minutes after discontin- second hour of the perfusion period. The peptide uation of the infusion. histidine isoleucine vehicle (sodium chloride containing human serum albumin) was infused EFFECT OF PEPTIDE HISTIDINE ISOLEUCINE ON intravenously for the first (pre-peptide histidine WATER AND ELECTROLYTE TRANSPORT isoleucine) and third (post-peptide histidine Peptide histidine isoleucine caused a significant isoleucine) hours. The infusion rate for each period reduction in the net jejunal absorption of water, was 50 ml/h. Pulse and blood pressure were potassium and bicarbonate, virtually abolished net recorded at 15 minute intervals throughout each sodium absorption and reversed the direction of net experiment. Venous blood samples were collected chloride absorption to a net secretion (Table). at 15 minute intervals from an indwelling cannula These effects of peptide histidine isoleucine into heparinised tubes containing 0-2 ml Trasylol/10 developed within 10 minutes of starting peptide ml blood, centrifuged immediately, and the plasma histidine isoleucine infusion and reversed equally stored at -20°C. rapidly after its discontinuation. For each of the pre-peptide histidine isoleucine, peptide histidine ANALYSIS OF SAMPLES AND CALCULATIONS isoleucine and post-peptide histidine isoleucine The concentration of sodium, potassium, chloride, periods, net transport of water and ions achieved bicarbonate, and [14C]PEG was determined in each steady state values after an equilibration period of was in an LKB aspirate. [14C]PEG measured 1210 30 minutes. Therefore, the results represent the http://gut.bmj.com/ Ultrobeta liquid scintillation counter.'( Sodium and mean net transport values calculated from analysis potassium concentrations were measured using an of three consecutive aspirates collected during 30-60 EEL 227 flame photometer (Evans Electroselenium minutes of each of the three study periods. Ltd, Halstead, Essex) and chloride by an EEL chloridometer. Bicarbonate concentrations were derived from measurement of pCO2 using an automated Corning 965 CO2 analyser (Corning Ltd, on September 27, 2021 by guest. Protected copyright. Halstead, Essex). Absorption rates of water and 3000- solutes from the test segment were calculated from their measured concentrations in the perfusate and aspirates." Net absorption (+) indicates a net transfer of water or solute from the lumen; net 2000. secretion (-) indicates net transfer of water or solute into the lumen. PEPTIDE HISTIDINE ISOLEUCINE 1000* RADIOIMMUNOASSAY Plasma samples for determination of peptide histidine isoleucine were stored at -20°C until PHI assayed in one batch. The specific radioimmuno- 0- 4 assay used showed no cross-reactivity with VIP, r- E s secretin, glucagon or gastric inhibitory polypeptide -30 0 30 60 90 12120 and had a lower limit of detection of approximately (minm) 10 pmol/1.5 Figure Plasma peptide histidine isoleucine concentrations in pmolll are represented on the vertical axis and time in STATISTICAL METHODS minutes on the horizontal. Peptide histidine isoleucine was Statistical analyses were performed using the paired infused at a rate of44-5 pmollkglmin. Results are the means Student's t test.12 ± SEMfor six subjects. Gut: first published as 10.1136/gut.25.6.624 on 1 June 1984. Downloaded from 626 Moriarty, Hegarty, Tatemoto, Mutt, Christofides, Bloom, and Wood Table Effect ofpeptide histidine isoleucine on jejunal The effects of peptide histidine isoleucine in human water and ion transport jejunum are similar to those previously reported in the small intestine of the and rat,7 Peptide pig6 and in guinea Pre- histidine Post- pig gall bladder.8 Similar changes in water and ion peptide isoleucine peptide transport in human jejunum were produced by histidine (44-5pmoll histidine infusion of VIP.13 14 While peptide histidine isoleucine kglmin) isoleucine isoleucine appears to be less potent than VIP in the Net water transport human jejunum, studies in guinea pig gall bladder (ml/30 cm/h) 192.3±29.4 48-7+13-7* 181-7±27-7 have shown that the two peptides are equipotent Net sodium transport inhibitors of fluid absorption.8 l5 (mmol/30 cm/h) 23 5±4-6 0-5±2-4* 20 5±4-3 Secretagogues may influence jejunal water and Net potassium transport (mmol/30 cm/h) 1-12±0-15 0-51±0-10t 1-10±0-17 electrolyte absorption by a variety of mechanisms. Net chloride transport Vasoactive intestinal peptide has been reported to in- (mmol/30 cm/h) 10-6±2.7 -6-3±2-3t 9-3±2.0 hibit both active bicarbonate absorption and passive Net bicarbonate transport movement of sodium
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