D Kosik-Bogacka | PubMed Health

PubMed2004

Ion transport in rabbit caecum at 12 and 36 months of age.

The aim of this study was to investigate the effect of aging on sodium and chloride ions transport in the isolated rabbit caecum. The experiment consisted in measuring PD- transepithelial electrical potential difference mV SM-mechanical stimulation and mechano-sensitivity (dPD) in collected from 12- and 36-month-old rabbits. A modified Ussing system was used for the experiment. Under the incubation in Ringer solution the values of PD and dPD of young rabbit caecum were, respectively, -3.0 +/-0.4 mV and -1.2 +/-0.3 mV. In 36-month rabbits, on the other hand, the values of these parameters were lower, PD by about 90% whereas dPD by about 83%. Incubation of young rabbits caecum with the presence of amiloride resulted in a reduction of PD by about 17 % and dPD by about 50%, while it did not influence the electrophysiological parameters of caecum in 36-month rabbits. Incubation with bumetanide on young rabbits caecum resulted in PD dropped by about 70% and dPD by about 83%. In the same incubation conditions as those applied for incubation of 36-month rabbits caecum, the level of PD decreased by about 67% while dPD by about 50%. Incubation of young rabbits caecum at the presence of both transport inhibitors resulted in PD decreased by about 87% and dPD by about 83%, whereas that applied for the old rabbits' caecum reduced PD by about 90%, without influencing dPD. Presented data demonstrate that the process of organism ageing inhibits sodium ion transport as well as reduces caecum epithelium sensitivity to mechanical stimuli. Probably, it is a consequence of a reduced with age release of neurotransmitter from sensory terminals; these neurotransmitters modify transepithelial ion transport.

Age Factors↗

PubMed2001

[Model experiments of physiologic and pharmacologic interactions with epithelial ionic currents induced by stimulation of sensory receptors ].

The present experiments were conducted to reveal regulatory mechanisms that control the stable electric potential (PD) and reversible changes in this potential during mechanical stimulation (dPD). The aim of the present work was to determine the role of C fibre endings and adrenergic and cholinergic receptors in the regulation of ion transport and to assess the applicability of frog skin as a model for physiological and pharmacological analysis of sodium and chloride currents. The experimental material consisted of 413 fragments of frog skin from 139 animals. Cross-epithelial electric potential (PD in mV) and electric resistance (R in ohms) of isolated frog skin placed in Ussing apparatus were measured. Mechanical stimulation of sensory receptors resulted in reversible hyperpolarisation (Tab. 1, Fig. 1). Preincubation of frog skin in the presence of amiloride (AMI) completely inhibited this reaction (Tab. 1, Fig. 2a), whereas incubation in bumetanide (BUME) lowered PD and did not induce hypersensitivity to mechanical stimuli (Tab. 1). Addition of capsaicin (KAPSA) to the preparations incubated in Ringer's solution (RH) and in Ringer's solution reinforced with BUME resulted in depolarisation (Tab. 1). On the other hand, incubation with KAPSA caused hyperpolarisation in the AMI group. KAPSA supplementation influenced the sensitivity to mechanical stimulation in all experimental groups. It was found that ambroxol (ABX) added to the preparations incubated in RH solution and in BUME, inhibited the hyperpolarisation and did not affect the magnitude of the reaction in the AMI group (Tab. 2, Fig. 3). ABX administration caused a decrease in the reactivity to mechanical stimuli in the RH group. Blocking of both adrenergic and cholinergic receptors with a solution containing thymolol, benextramine, hexamethonium, and atropine (ABHT) inhibited the hyperpolarisation in all groups studied and was without effect on the magnitude of mechanical stimulation in AMI and BUME groups (Tab. 2). In the RH group, ABHT weakened the reaction to mechanical stimulation. Changes in the pH of Ringer's solution (pH 6.4) caused a decrease in the electric potential and in the reactivity to mechanical stimuli, without altering resistance (Tab. 3). Addition of toluene diisocyanate (TDI) to preparations incubated in RH solution and in AMI increased the hyperpolarisation (Tab. 4). TDI also led to changes in the reaction to mechanical stimulation, i.e. induced depolarization in both groups. On the other hand, TDI administration to frog skin incubated with BUME did not cause any reaction change. The following conclusions were drawn from the present findings: 1. Hyperpolarisation caused by physiological and pharmacological stimuli is effected principally through increased sodium flux. 2. Stimulation of C fibre endings, as well as of adrenergic and cholinergic receptors, inhibits ion transport. 3. Isolated frog skin is a useful model for studying sodium and chloride transport through mammalian epithelium.

Amiloride↗