EFFECTS OF DIETARY DEPRIVATION ON SMALLAND LARGE INTESTINAL ION TRANSPORT IN THE MOUSE

Abstract

The aim of this work is to investigate the effects of nutritional levels on the secretory functions of the small and large intestine in the mouse. The study was carried out on male swiss strain adult mice (of approximate 700) weighing 2040 gr. Mice starvedfor 48h refed after 48h starvation allowing themfood ad lib. Mice were also undernourishedfor 4d with 50% (3grlper mouselper day) of the fed control adult daily food intake. Experimental data was collectedfrom mice smaIl (midjejunum and proximal ileum) and large intestine (proximal, mid and distal colon). In mid jejunum and proximal Ueum, funetionaIly distinct differences were observed by their bioelectric properties [i.e potential difference (PD.), tissue resistance (R) and basal short-circiuit current (Isc)). These were altered by changes in nutritional status in the mid jejunum, while those of the proximal ileum remained unchanged. Three functionaIly distinet eolonie segments (proximal, mid and distal) were identified by their bioeleetrie properties (P.D., R and basal Ise) which varied along the eolon. These properties were altered by changes in nuıritional status. When stimulated to secrete the 48h starved mid jejunum and proximal ileum did not exhibit a hypersecretory response to the Ca2+ acting secretory agonists (bethaneehol, 5-HT) and DbeAMP. In the eolon, after 48h starvation bethaneehol aetivated a higher eleetrogneic seeretion that in the fed controls. The response of the distal colon to bethaneehol was biphasic. In the proximal and mid colon, in the case of food deprivation, cye/ic nue/eotide acting secretory agonists (DbcAMP, theophylline) did not aetivate a hypersecretory response compared to the fed colons. In the starved proximal colon, atropine potentiared 5-HT-indueed inerease in Ise and this was significantly larger than that in thefed. In the sma// and large intestine, CI. replaeement by glueonate in vitro, indicated that the basa i and eholinergie secretagogue stimulated seeretion were mainly carried by the C]- ion. In the ease of starvation, in the sma// intestine in vivo, the basal and bethanechol-stimulated fluid transport eonflrmed the lack of secretion obtained in vitro. In the colon, however, the in vivo results did not confirm the hypersecretion induced by bethanechol in vitro.