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  • Stripping  (2)
  • Bumetanide  (1)
  • Corticosterone plasma concentration  (1)
  • 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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  • 2
    Electronic Resource
    Electronic Resource
    Time course of aldosterone and corticosterone plasma levels in rats during general anaesthesia and abdominal surgery (1983)
    Springer
    Pflügers Archiv 399 (1983), S. 249-254 
    Details
    ISSN: 1432-2013
    Keywords: Aldosterone plasma concentration ; Corticosterone plasma concentration ; Anaesthesia ; Barbiturates ; Abdominal surgery ; Large intestine ; Transepithelial potential difference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The transepithelial voltage (Ψ ms) of rat rectum in vivo increases for several hours in experiments under general anaesthesia. So far this was attributed by indirect evidence to increasing aldosterone plasma levels during the course of the experiment. We performed direct measurements of aldosterone and corticosterone plasma concentrations during intestinal perfusion experiments on barbiturate anaesthetized rats. Experiments were terminated for blood sampling at 10, 75, 300, 400, 800, or 1,800 min, respectively. (i) After 75 min of anaesthesia, surgical preparation was finished and plasma levels of aldosterone and of corticosterone were found increased by the factors 5 and 3, respectively, as compared to conscious controls. (ii) During the following 12 h, aldosterone further increased to levels 10 times as high as those of controls. In contrast, during the same period corticosterone slowly decreased but still remained elevated as compared to controls. (iii) The increase of both hormones was attenuated when abdominal surgery was omitted. (iv) The use of pentobarbital (Nembutal) instead of thiobarbital (Inactin) did not influence the adrenal response. (v) In adrenalectomized rats a continous substitution with 65 ng·h−1·kg−1 BWT aldosterone resulted in plasma levels as high as in conscious intact animals. (vi) RectalΨ ms started to move to higher lumen-negative values with a time delay of 1–1 1/2 h as compared with the increase of hormone levels.Ψ ms then stayed elevated until to the end of the experiments. We conclude that in vivo experiments of several hours duration in thio- or pentobarbital anaesthetized rats take place under conditions of aldosterone and corticosterone plasma levels which are high as compared to those of conscious unstressed animals. The different time course of aldosterone and corticosterone plasma levels after the end of surgery would be in accord with a stimulatory effect of anaesthesia on both renin and ACTH, plus an additional stimulatory effect of abdominal surgery on ACTH alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652747
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Epithelial and subepithelial resistance of rat large intestine: segmental differences, effect of stripping, time course, and action of aldosterone (1986)
    Springer
    Pflügers Archiv 407 (1986), S. 632-637 
    Details
    ISSN: 1432-2013
    Keywords: Colon ; Rectum ; Epithelial resistance ; AC impedance ; Stripping ; Subepithelial resistance ; Aldosterone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Epithelial and subepithelial electrical resistances of rat large intestine were measured by means of a 4-electrode AC impedance technique in three segments, colon ascendens, colon descendens and rectum. (i) Epithelial resistance of colon ascendens and colon descendens was about 35 Ω · cm2 and not different between these two segments. It was, however, about 3 times higher in rectum (99 Ω · cm2). This finding is in accord with our previous observation of about 3-fold higher net fluxes of ions and water in colon ascendens and colon descendens than in rectum. It confirms the concept of a main functional difference between the terminal part of the large intestine (rectum) and the more proximal segments (colon). (ii) The acutely (within hours) varied level of aldosterone by keeping the rats for 7 h in anaesthesia caused in the rectum a more than 10-fold increase in short circuit current (I SC) and transepithelial voltage but no significant decrease in resistance. Similarly, the decline inI SC, as regularly observed in the early phase of in vitro measurements on partially stripped large intestine, was paralleled by voltage changes but not by changes in resistance. We conclude that the wide range of resistance values published so far was caused to a great extent by including various portions of colon or rectum. (iii) By comparing intact (not stripped) and partially stripped preparations (muscularis propria removed) of the rectum it was shown that partial stripping did not alter the epithelial resistance but reduced the subepithelial resistance in this segment from 26 to 8 Ω · cm2, or by 68%. Subepithelial resistances of stripped rectum, colon ascendens and colon descendens were 8, 12 and 13 Ω · cm2, respectively. Based on these figures,I SC of conventional voltage clamp measurements is underestimated due to subepithelial tissue layers in intact rectum by 23% and in the partially stripped preparations of rectum, colon ascendens and colon descendens by 9%, 34%, and 37%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582644
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    Paper (German National Licenses)
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