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  • 1
    Electronic Resource
    Electronic Resource
    Ion transport and enteric nervous system (ENS) in rat rectal colon: Mechanical stretch causes electrogenic Cl-secretion via Plexus Meissner and amiloride-sensitive electrogenic Na-absorption is not affected by intramural neurons (1989)
    Springer
    Pflügers Archiv 414 (1989), S. 216-221 
    Details
    ISSN: 1432-2013
    Keywords: Amiloride ; Bumetanide ; Cl-secretion ; Electrical field stimulation ; Large intestine ; Na-absorption ; Rat ; Stripping ; Submucosal plexus ; Tetrodotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The initial phase of in vitro experiments in Ussing-type chambers on large intestine is characterized by short-circuit currents (ISC) declining from high starting values to a lower plateau within 0.5 h. The origin of this “initial ISC-transient” was investigated by ISC measurements on partially stripped segments of rat rectal colon. Transport was pre-stimulated in vivo by keeping animals in barbiturateanesthesia for 5 h prior to tissue preparation. This procedure caused by endogenous aldosterone-liberation amiloride-sensitive Na-absorption to become the predominant electrogenic transport. The initial ISC-transient was abolished by tetrodotoxin (TTX, 1 μM), indicating a neuronal mediation of this phenomenon. In order to identify the transport which was subject to neuronal control, the amiloride-sensitive Na-absorption was measured during electrical field stimulation (bipolar rectangular pulses: 5 Hz, 1 ms, ±6 mA). There was no difference to unstimulated controls. In contrast, the initial ISC-transient was dependent on Cl in the bath following Michaelis-Menten-kinetics (K M=20 mM) and could be prevented by 10 μM serosal bumetanide. Then, initial filling of the Ussing-chamber was imitated during the course of the experiment by removal and immediate readdition of the bathing fluid. This procedure caused ISC-changes of similar appearance as the initial ISC-transient. To verify that indeed mechanical stretch is the sensory stimulus triggering the initial ISC-transient, the effect of small pressure oscillations was studied. This also produced an ISC-transient which was TTX-sensitive and was abolished after removal of the submucosal plexus Meissner by total stripping. It is concluded that amiloride-sensitive Na-absorption does not contribute to the initial transient and is not affected by the enteric nervous system. Initial ISC-transients asobserved during the first half hour of Ussing experiments are due to electrogenic Cl-secretion which is stimulated by mechanical stretch during tissue preparation and filling of the chamber via a submucosal neuronal reflex pathway. The possible biological meaning of this stretch-induced secretory process could be facilitation of transit during imminent stasis of the gut contents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00580966
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Three-day continuous drainage of pancreatic juice in the cortisone-treated conscious rat: Analysis of enzyme activities and ultrastructural changes (1985)
    Springer
    Cell & tissue research 242 (1985), S. 191-196 
    Details
    ISSN: 1432-0878
    Keywords: Exocrine pancreas ; Rat ; Cortisone ; Ultrastructure ; Enzyme secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We have investigated the short-term effects of hydrocortisone (60 mg/kg per day) and placebo on basal and stimulated pancreatic secretion in the conscious rat. Volume and enzyme secretion were determined; fine structural changes were examined simultaneously. The pancreatic and bile ducts were cannulated separately; pancreatic juice was drained via an isolated fistula, and bile was recirculated into the duodenum. The application of hydrocortisone led to an almost complete inhibition of the secretory response of the exocrine pancreas when stimulated with 0.25 U secretin in combination with 5 × 10-8 g caerulein per h. It strongly affected the secretion rates of volume, protein, lipase, chymotrypsin, trypsin and carboxypeptidase, whereas the secretion rate of alpha-amylase continued to show a slight increase after stimulation. After stimulation with secretin and caerulein, the hydrocortisone-treated animals showed a higher density of zymogen granules in the acinar cell and an increase in the number of autophagic vacuoles in comparison to the equally stimulated placebo-treated rats. It is concluded that the short-term inhibition of pancreatic secretion by hydrocortisone occurs largely as a result of an inhibition of cellular enzyme discharge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225576
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    Paper (German National Licenses)
    Fulltext
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