Immunohistochemical study on the endocrine cells in gut of the stomachless teleost, Zacco platypus (Cyprinidae)

The regional distribution and relative frequency of neurohormonal peptides-producing cells were demonstrated in the gut of the stomachless teleost, Zacco platypus (Temminck et Schegel), using 10 types of specific antisera raised against mammalian regulatory peptides. The gut of Z. platypus was divided into five portions from proximal to distal (segment I-V). Most of immunoreactive cells in the epithelial lining portion, between epithelial cells, were generally spherical or spindle shape having long cytoplasmic process that was reached via the lumen while cells round in shape were found in the basal portions of epithelial lining occasionally. Serotonin-, somatostatin-, glucagon-, cholecystokinin (CCK)-8 and pancreatic polypeptide (PP)-immunoreactive cells were observed in this study. However, no chromogranin A-, secretin-, vasoactive intestinal peptide (VIP)-, substance P- and bombesin-immunoreactive cells were found. Serotonin-immunoreactive cells were demonstrated throughout the entire gut tract and occurred more frequently than other cells. Somatostatin-immunoreactive cells were restricted to proximal segments of the gut (segment I-III) with rare frequencies, and glucagon-immunoreactive cells were demonstrated in the proximal segments of the gut (segment I, II) with moderate to few occurrences. CCK-8-immunoreactive cells were found throughout the whole intestinal tract except for most proximal segment (segment I) with moderate to few frequencies and PP-immunoreactive cells were demonstrated in the proximal to middle segments, segment I-III, with a few, rare and rare frequencies, respectively.