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Does the ostrich (Struthio camelus) coprodeum have the electrophysiological properties and microstructure of other birds?

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  • 1Department of Anatomy and Physiology, Royal Veterinary and Agricultural University, DK-1870 Copenhagen, Denmark.

Abstract

The ostrich is unique among birds in having complete separation of urine and faeces. The coprodeal epithelium is thus during dehydration exposed to a fluid 500 mOsm hyperosmotic to plasma. We have investigated whether the coprodeum is adapted like a mammalian bladder. The coprodeal epithelium was studied by electrophysiology in the Ussing chamber, and the anatomy by light microscopy and scanning electron microscopy.

ELECTROPHYSIOLOGY:

The short-circuit current (SCC) and open circuit electrical potential difference were recorded. The change induced by 0.1 mmol mucosal amiloride was recorded. An average basal SCC of 162+/-29 microA/cm(2) was observed, and a resistance of 297+/-34 Omega cm(2) calculated. These values are as observed in other avian coprodea. The resistance is much lower than in mammalian bladders (10000 Omega cm(2)). The amiloride-sensitive SCC, equal to net sodium absorption, was approximately 5 micromol/cm(2)h as observed in other avian species.

ANATOMY:

The mucosal membrane is composed of broad irregular folds with very short intestinal glands containing an unusually high proportion of goblet cells.

CONCLUSION:

The ostrich coprodeum is not adapted like a mammalian bladder. The abundance of goblet cells results in a copious secretion of mucus that establishes a thick unstirred layer giving effective osmotic protection.

PMID:
12814783
[PubMed - indexed for MEDLINE]
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