Neurohumoral control of esophageal epithelial electrolyte transport D. D. BOYD, C. N. CARNEY, AND D. W. POWELL (With the Technical Assistance of D. R. Etheridge) Departments of Medicine and Pathology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27514 BOYD, D. D., C. N. CARNEY, AND D. W. POWELL. Neurohu- moral control of esophagealepithelial electrolyte transport. Am. J. Physiol. 239 (Gastrointest. Liver Physiol. 2): C5-Gll, 1980.-The neurohumoral control of epithelial esophageal elec- trolyte transport was investigated by studying the effect of various hormones and neuroeffector agents on the potential difference (PD). in vivo or on the electrical parameters or electrolyte transport in vitro. The rabbit esophagus, which has no submucosal esophageal glands, demonstrated no effect of pentagastrin, cholecystokinin octapeptide, or synthetic secretin in vivo, and no effect of these hormones or of vasopressin, aldosterone, carbachol, epinephrine, or CAMP in vitro. The rabbit esophagus did respond to metabolic substrates (glucose) in vitro by increasing sodium absorption. In contrast, the opos- sum esophagus, which contains extensive submucosal glands, had a lower electrical resistance, PD, short-circuit current, and sodium absorption with higher chloride secretion. This esoph- agus responded to carbachol and epinephrine by sodium and chloride secretion. We believe that only the submucosal glands of the esophagus are under significant neurohumoral control while the sodium transporting function of the stratified squa- mous epithelium of this organ is important in maintaining its barrier function. rabbit; opossum; hormones; neuroeffector agents; gastrin; cho- lecystokinin; secretin; vasopressin; aldosterone; carbachol; epi- nephrine; sodium and chloride transport; stratified squamous epithelium EPITHELIA, regardless of type or location, have two gen- eral functions: first, to serve as a protective barrier, and second, to transport substances (usually nutrients, elec- trolytes, or water) from one side of the barrier to the other. Study of the transport functions of epithelia have been particularly rewarding in the past 50 yr, and the gastrointestinal tract has been fertile ground for such research. We have recently demonstrated that the strat- ified squamous epithelium of the rabbit esophagus trans- ports electrolytes and water (9). The physiological signif- icance of this transport function has remained obscure. It seems unlikely that the esophagus plays any funda- mental role in water and electrolyte conservation because its electrolyte and water transport rates are extremely low, and because the residence time is extremely short for any fluid and electrolyte in the esophagus. Electrolyte transport by this organ could, however, be a vestigial function of any foregut epithelium. Alternatively, electro- lyte and water transport may be important in maintain- ing the architecture of this epithelial barrier. Seeking further insight into the physiology and control of this transport function, we have investigated the effect of various hormones and neuroeffector agents on Na and Cl transport by the esophageal mucosa of both rabbit and opossum. METHODS The methods of study of the transport function of the esophageal epithelium ,have been outlined previously in detail (9). In in vivo experiments, male New Zealand Albino rabbits weighing 2-3 kg were anesthetized with intravenous pentobarbital sodium (20 mg/kg) and main- tained with small periodic doses of a 1:l mixture of pentobarbital(65 mg/ml) and diazepam (5 mg/mI). Body temperature was mainlined at 38OC with a heating pad. A tracheostomy was performed and the esophagus can- nulated at the level of the thyroid cartilage and at the gastroesophageal junction. At the time of cannulation, an agar bridge (PE-205 containing 4% agar dissolved in Ringer solution) was passed into the esophagus. A ref- erence bridge of similar type was placed outside the esophagus at either the thoracic inlet or in the region of the gastroesophageal junction. Both free ends of the agar bridges were inserted into beakers of saturated KC1 so- lution containing calomel reference electrodes connected to a high-impedance voltmeter (Model 610-B electrome- ter, Keithly Instruments, Cleveland, OH). The esophagus was rinsed and perfused at the rate of 8 mI/min with a Ringer solution of the following composition: 140 mM Na, 5.2 mM K, 119.8 mM Cl, 25 mM HCOa, 1.2 mM Ca, 1.2 mM Mg, 2.4 mM HzP04, 6.4 mM HP04, and 10 mM mannitol. The electrical transmural potential difference (PD) was recorded every 15 ‘min during 180 min of perfusion. Forty-five and ninety minutes after the start of perfusion, the animals were given intravenous injec- tions, via the ear vein, of one of three gastrointestinal hormones over a l-min period. Five experiments were performed with pentagastrin at an initial intravenous bolus dose of 1.0 pg/kg and a second dose of 5.6 pg/kg. Four experiments were performed with synthetic secretin with an initial dose of 0.8 pg/kg and a second bolus dose of 4.0 pg/kg. Seven experiments were performed with the cholecystokinin octapeptide (CCK-OP) at doses initially of 50 rig/kg and then increased to 200 rig/kg. The first dose of each hormone used was that previously reported 0193-1857/80/0000-0000$01.25 Copyright 0 1980 the American Physiological Society G5 Downloaded from journals.physiology.org/journal/ajpgi at Univ of Texas Med Branch Lib (129.109.110.005) on August 26, 2022.