AJP - Gastrointestinal and Liver Physiology, Vol 253, Issue 5 690-G696, Copyright © 1987 by American Physiological Society
Secretagogue-induced changes in intracellular pH and amylase release in mouse pancreatic acini
K. J. Carter, P. L. Rutledge, M. L. Steer and W. Silen
Department of Surgery, Beth Israel Hospital, Boston, Massachusetts 02215.
The response of the intracellular pH (pHi) to stimulation of enzyme
secretion in pancreatic acini was measured using the fluorescent dye
2'-7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Acini suspended in pH 7.40
buffer demonstrated cytoplasmic alkalinization of 0.17, 0.14, and 0.15 pH
units 2 min after addition of the secretagogues carbachol (10(-5) M),
caerulein (10(-10) M), and bromo-A23187 (10(-6) M). Corresponding net
stimulated amylase secretion over 30 min was 9.2, 10.3, and 5.6% of total
content, respectively. Pretreatment of acini with atropine blocked the pHi
rise induced by carbachol; addition of atropine 2 min after the carbachol
did not reverse the alkalinization. Acini suspended in Ca2+ free buffer
containing 0.1 or 0.2 mM ethylene glycol tetraacetic acid showed 0.21 and
0.10 pH unit alkalinization in response to caerulein (10(-10) M) and
carbachol (10(-5) M) but no change in pHi after addition of bromo-A23187.
Amylase release in response to increasing concentrations of caerulein was
maximal at 10(-10) M, with decreasing rates of amylase release at higher
drug concentrations (10(-8), 10(-7) M). Alkalinization in response to
stimulation of secretion was maximal at 10(-8) M caerulein (0.30 pH units
at 2 min) but was of lesser magnitude at 10(-7) M. Pancreatic acini
demonstrated autoregulation of pHi over a range of external pH from 7.4 to
7.1. Net amylase release over 30 min in response to 10(-5) M carbachol was
sustained at normal levels in buffers of pH varying between 7.7 and 6.5. In
contrast, cytoplasmic alkalinization in response to carbachol occurred only
in buffers with pH values between 7.40 and 7.10. These results indicate
that amylase release occurs over a wide range of pHi and is not invariably
associated with secretagogue-induced alkalinization.
