Histochemical and immunohistochemical evidence for a gradient in gastric juice production in the greater horseshoe bat, Rhinolophus ferrumequinum (Schreber, 1774)

Histochemical and immunohistochemical investigations were performed on the gastric mucosa of the greater horseshoe bat, Rhinolophus ferrumequinum (Schreber, 1774) to estimate the presence of a gradient of pepsinogen and hydrochloric acid along an oro-aboral axis of the stomach, similar to that found in some non-mammals. Paraffin sections were stained with DBA-lectin binding, Bowie and fluorescent anti-H+/K+- ATPase α-subunit immunostaining to detect the chief and parietal cells in the gastric mucosa. The stomach of the bat presents a short cardias, a wide fundus and a small pylorus. Chief and parietal cells were found in the fundic glands and their number varied from the oral to the aboral region of fundus. In the oral region several chief cells with Bowie-positive pepsinogen granules were observed in the basal part of glands, whereas parietal cells positive to DBA-lectin binding and immuroreactive with anti-H+/K+-ATPase α-subunit were concentrated in the the upper part of the glands. In the aboral fundus chief cells were lacking, whereas the number of parietal cells increased and they were distributed along the glands. A gradient of pepsinogen and hydrochloric acid secretion similar to that found in some non-mammals can be hypothesised. The possibility that this gradient is the ancestral condition in Chiroptera and Eutheria and its functional meaning are discussed.