Villanger O, Veel T, Raeder M G
Institute for Experimental Medical Research, University of Oslo, Norway.
Gastroenterology. 1995 Mar;108(3):850-9. doi: 10.1016/0016-5085(95)90460-3.
BACKGROUND/AIMS: Secretin stimulates pancreatic ductules to secrete HCO3- into pancreatic juice and H+ into interstitial fluid. The aim of the present study was first to examine whether ductular H+ secretion is inhibited by micromolar concentrations of bafilomycin A1, which blocks vacuolar H(+)-adenosine triphosphatase by specific action, and secondly to test for evidence of ductular Na+/HCO3- cotransport.
Ductular H+ secretion was estimated from the rate of intracellular pH recovery after acid-loading (24 mmol/L NH4Cl) microdissected pancreatic ductules from pig, mounted in a flow-through perfusion chamber on the stage of a fluorescent microscope. Intracellular pH was measured using the fluorescent pH indicator 2'7'-bis (carboxyethyl)-5,6-carboxyfluorescein and dual-wave-length excitation of fluorescence. The ducts were superfused perfused with either HCO3(-)-free HEPES-containing buffers or HCO3(-)-containing buffers.
Secretin (10(-8) mol/L) induced a net H+ secretion of 1.87 +/- 0.23 mumol.mL cell vol-1.min-1 that was blocked by 10(-6) mol/L bafilomycin A1 and was unaffected by Na+ substitution with choline using HEPES superfusion buffers. Secretin-stimulated ductules superfused with bicarbonate-containing, Cl(-)-free buffers showed Na(+)-dependent and 4,4'-diisothiocyanostilbene-2, 2'-disulfonic acid-inhibitable alkalinization of intracellular pH.
Secretin causes H+/HCO3- secretion from pancreatic ductules by a mechanism involving vacuolar-type H(+)-adenosine phosphatase. Pancreatic ductules also show Na+/HCO3- cotransport, which may account for a small fraction of secreted bicarbonate.
背景/目的：促胰液素刺激胰腺小导管向胰液中分泌HCO3-，并向细胞间液中分泌H+。本研究的目的首先是检测微摩尔浓度的巴弗洛霉素A1是否抑制小导管H+分泌，巴弗洛霉素A1通过特异性作用阻断液泡H(+)-腺苷三磷酸酶；其次是检测小导管Na+/HCO3-协同转运的证据。
通过酸负荷（24 mmol/L NH4Cl）后细胞内pH恢复速率来估计小导管H+分泌，酸负荷后的猪胰腺小导管在荧光显微镜载物台上的流通灌注室中进行显微解剖。使用荧光pH指示剂2'7'-双（羧乙基）-5,6-羧基荧光素和双波长荧光激发来测量细胞内pH。小导管用不含HCO3(-)的含HEPES缓冲液或含HCO3(-)的缓冲液进行灌流。
促胰液素（10(-8) mol/L）诱导净H+分泌为1.87±0.23 μmol·mL细胞容积-1·min-1，该分泌被10(-6) mol/L巴弗洛霉素A1阻断，并且在使用HEPES灌流缓冲液用胆碱替代Na+时不受影响。用含碳酸氢盐、不含Cl(-)的缓冲液灌流的促胰液素刺激的小导管显示细胞内pH呈Na(+)依赖性且可被4,4'-二异硫氰基芪-2,2'-二磺酸抑制的碱化。
促胰液素通过涉及液泡型H(+)-腺苷磷酸酶的机制引起胰腺小导管分泌H+/HCO3-。胰腺小导管也显示Na+/HCO3-协同转运，这可能占分泌的碳酸氢盐的一小部分。
