Odes H S, Hogan D L, Steinbach J H, Ballesteros M A, Koss M A, Isenberg J I
Dept. of Medicine, UCSD Medical Center.
Scand J Gastroenterol. 1992 Oct;27(10):829-36. doi: 10.3109/00365529209000149.
Human gastric bicarbonate secretion has been measured by back-titration, from pH and pressure of carbon dioxide (PCO2) determinations (using the Henderson-Hasselbalch formula), and from equations based on gastric juice osmolality and [H+] (osmolality-[H+] method). Since these methods show large quantitative differences in their estimations of gastric bicarbonate secretion, we examined each to define the reasons for these discrepancies and establish guidelines for future work in this area. Bicarbonate recovery from 'non-parietal' secretions (0 to 80 mM HCO3) reacting with 'pure parietal secretion' (160 mM HCl) was studied both in vitro and in the pylorus-occluded healthy human stomach during acid suppression, exogenous acidification, and pentagastrin stimulation. The pH/PCO2 method estimated HCO3- accurately under anaerobic conditions in vitro, whereas the osmolality-[H+] method (with correction factors for osmolality incorporated by us) was accurate under aerobic conditions. In the acid-suppressed stomach back-titration was significantly more accurate than the pH/PCO2 method. In the exogenously acidified and pentagastrin-stimulated stomachs the pH/PCO2 method underestimated bicarbonates, and the osmolality-[H+] method was spuriously elevated in the low range and diminished at high bicarbonate concentrations. Estimates of 'basal' bicarbonate secretion (at zero added bicarbonate) were severalfold higher by the osmolality-[H+] method (5.26 +/- 0.33 mmol/h) than by the pH/PCO2 method (1.20 +/- 0.23 mmol/h) or back-titration (0.65 +/- 0.14 mmol/h). In conclusion, gastric bicarbonate was determined most correctly by back-titration in the acid-suppressed stomach, whereas measurement of bicarbonate in the acid-secreting stomach was not accurate with any method.
回滴法、根据酸碱度和二氧化碳分压（PCO₂）测定值（使用亨德森 - 哈塞尔巴尔赫公式）以及基于胃液渗透压和[H⁺]的公式（渗透压 - [H⁺]法）。由于这些方法在估计胃碳酸氢盐分泌量时存在较大的定量差异，我们对每种方法进行了研究，以确定这些差异的原因，并为该领域未来的研究制定指导方针。在体外以及幽门闭塞的健康人胃中，分别在胃酸抑制、外源性酸化和五肽胃泌素刺激期间，研究了“非壁细胞”分泌物（0至80 mM HCO₃）与“纯壁细胞分泌物”（160 mM HCl）反应时碳酸氢盐的回收率。pH/PCO₂法在体外厌氧条件下能准确估计HCO₃⁻，而渗透压 - [H⁺]法（我们纳入了渗透压校正因子）在需氧条件下是准确的。在胃酸抑制的胃中，回滴法比pH/PCO₂法显著更准确。在外源性酸化和五肽胃泌素刺激的胃中，pH/PCO₂法低估了碳酸氢盐，而渗透压 - [H⁺]法在低浓度范围内假性升高，在高碳酸氢盐浓度时降低。“基础”碳酸氢盐分泌量（添加碳酸氢盐为零时）的估计值，渗透压 - [H⁺]法（5.26±0.33 mmol/h）比pH/PCO₂法（1.20±0.23 mmol/h）或回滴法（0.65±0.14 mmol/h）高出数倍。总之，在胃酸抑制的胃中，通过回滴法能最准确地测定胃碳酸氢盐，而在胃酸分泌的胃中，任何方法都无法准确测量碳酸氢盐。
