Regulation of fluid secretion and intracellular messengers in isolated rat pancreatic ducts by acetylcholine.

Abstract

SUMMARY1. We have studied the effects of acetylcholine (ACh) on fluid secretion and intracellular messengers in interlobular ducts isolated from the rat pancreas and maintained in short-term tissue culture.2. Ductal fluid secretion was measured using micropuncture techniques.Intracellular free calcium ([Ca2+]1) and cyclic AMP concentrations were measured in single ducts using fura-2 microspectrofluorimetry and radioimmunoassay techniques respectively. Changes in the levels of these intracellular messengers were correlated with fluid secretion.3. ACh stimulated ductal fluid secretion. The dose required for a half-maximal response was about 0 4 ,/M and maximal secretion was achieved with 10 /LM ACh.These effects of ACh were blocked by atropine and by removal of extracellular Ca2". 4. ACh was about four orders of magnitude less potent as an activator of ductal fluid transport than the hormone secretin; however, the maximal rates of fluid secretion evoked by these two agonists were similar.5. ACh caused a dose-dependent rise in duct cell [Ca2+]i, but had no effect on cyclic AMP. In contrast, secretin increased duct cell cyclic AMP, but had no effect on [Ca2+]1. tTo whom reprint request should be sent.

Local uncaging of caged Ca 2+ reveals distribution of Ca 2+ -activated Cl − channels in pancreatic acinar cells

“…Therefore, the maximal rate of pancreatic fluid secretion stimulated by ACh or cholecystokinin is several orders of magnitude less (per unit of gland weight) than that achieved by, for example, the salivary glands (5). The difference becomes even more significant when one considers that part of the ACh-elicited pancreatic fluid secretion comes from the duct cells (39). The pancreatic acinar fluid secretion is nevertheless important for the washout into the duct system of the secreted acinar enzymes.…”

Evidence for a Na+−Ca2+ exchanger in rat pancreatic ducts

“…In the past few years, the number of ductal agonists has grown to include those that act via the Ca"+ transduction pathway, such as acetylcholine and ATP. Indeed, these agonists evoke marked Ca"+ transients in duct cells of rat pancreas [2,12,13,32]. Furthermore, pancreatic ducts have a rather high resting level of intracellular Ca*+ activity ([Ca"+]i), possibly correlating with the resting Clconductance [2 11, and spontaneous secretion [ 1,181.…”

Molecular and Functional Identification of a Ca2+ (Polyvalent Cation)-sensing Receptor in Rat Pancreas

“…The duct lumen was then perfused at a flow rate of 10 -20 l/min, while the chamber was perfused at a flow rate of 3.0 ml/min. Duct cell [Ca 2ϩ ] i or intracellular pH (pH i ) was estimated by dualexcitation wavelength microfluorometry as described previously (15,16). An optical diaphragm in the emitted light path limited fluorescence collection to a small region of the ductal epithelium (10 -20 cells ] i in isolated ducts contained (mM): 140 NaCl, 5 KCl, 10 D-glucose, and 10 HEPES, and was equilibrated with 100% O 2 .…”