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PubMed1965

MUCUS IN INTESTINAL CONTENTS OF GERMFREE RATS.

The fecal excretion of total nitrogen and of total hexosamines has been determined in germfree and conventional rats. Germfree rats excreted more hexosamines than the conventional rats, while no difference in the nitrogen excretion was found. Infection of the germfree rats with a normal flora resulted in a temporarily increased excretion of hexosamines and nitrogen over a period of 2 to 3 days after which they reached the level of the conventional animals. The contents of the germfree cecum contained 65 to 137 mg of hexosamines and 57 to 127 mg of nitrogen as compared to 1.2 to 5.3 and 7.4 to 23 mg in conventional animals. The high figures for hexosamines were due to an increase in the total amount of contents in the cecum and to a fivefold increase in the concentration of hexosamine-containing material. Studies on the distribution of hexosamine-containing cecal contents between sediment and supernatant after centrifugation at 20,000 g for 2 hours demonstrated that 5 to 10 per cent of the hexosamines occurred in the sediment in the germfree rats, while 75 to 85 per cent was found in this fraction in the conventional rats. The soluble part of the cecal contents in germfree as well as in the conventional rats contained 70 per cent of hexosamines in molecules with a molecular weight above approximatively 100,000 as found by gel filtration experiments on sephadex gels. The higher weight of the germfree cecal wall was reflected in a high total amount of nitrogen and hexosamines. Isolated strains of bacteria capable of reducing the cecal size in vivo did not show any capacity to degrade the mucus in vitro in a test system, where a full intestinal flora was highly active.

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PubMed1990

Comparison of the neuropeptide Y receptor in the rat brain and intestine.

Neuropeptide Y (NPY) is widely distributed in the central and peripheral nervous systems where it serves neuromodulator and neurotransmitter functions. NPY is contained within intrinsic nerves of the small intestine and can be demonstrated to inhibit intestinal secretion when added to the serosal side of intestine mucosa mounted in Ussing chambers. When injected centrally it has potent effects on food intake, blood pressure, sexual activity and circadian rhythms. Using NPY radiolabeled with iodogen, lactoperoxidase, or the Bolton-Hunter reagent, we have localized high-affinity NPY receptors on brain membranes and on the serosal laterobasal membranes of the rat intestinal epithelial cell. We have demonstrated that enzymatic degradation may limit the ability to demonstrate NPY binding to brush border membranes. In other experiments NPY was cross-linked to its receptors in brain and intestine using disuccinimido suberate and the resulting complexes analyzed on SDS polyacrylamide gel electrophoresis followed by radioautography. We identified two main NPY receptor species in the intestine with molecular sizes of 52-59 kDa and 37-39 kDa. The 37-39 kDa species may possess a disulfide bond which gives the receptor a fixed conformation, or it may be composed of two subunits (37-39 kDa and approximately 5 kDa subunits). This conclusion is based on the different migration of the smaller band in the presence of the reducing agent, dithiothreitol. The intestinal NPY receptor exhibits differences from the rat brain receptor previously characterized by us using similar techniques. The brain receptor has a molecular weight of approximately 58 kDa with a smaller species of about 35 kDa which shows no differences in migration after exposure to dithiothreitol. The localization of NPY receptors on laterobasal membranes and brain membranes is consistent with previous anatomic and physiologic findings. The different characteristics of each receptor type provides physical evidence of receptor heterogeneity. However, it is possible that the greater enzymatic degradation observed in intestinal membranes might explain the differences in receptor sizes in the two organs.

Animals↗