Gastroesophageal tube of the Iguana iguana (Iguanidae): histological description, histochemical and immunohistochemical analysis of 5-HT and SS cells

Tubo gastroesofágico da Iguana iguana (Iguanidae): descrição histológica, histoquímica e análise imunohistoquímica de células 5-HT e SS

Abstract

The work aims were to describe the histological and histochemical structure of the gastroesophageal tube of Iguana iguana and verify the occurrence and distribution of immunoreactive serotonin (5-HT) and somatostatin (SS) cells. Fragments of the gastrointestinal tract (GIT) of five iguanas were which underwent standard histological and immunohistochemistry technique. Immunoreactive cells for 5-HT and SS were quantified using the STEPanizer. The oesophagus has ciliated columnar pseudostratified epithelium with staining Alcian blue (AB) + and goblet cells highly reactive to periodic acid Schiff (PAS). In the cervical oesophagus, the numerical density of 5-HT cells per unit area (QA [5-HT cells]/µm²) was 4.6x10^-2 ± 2.0 and celomatic oesophagus presented QA = 4.0x10^-2 ± 1.0. The epithelium of the stomach is simple columnar, PAS and AB +. The cranial and middle regions of the stomach presented (QA [5-HT cells]/µm²) = 6.18x10^-2 ± 3.2 and the caudal region, QA = 0.6x10^-2 ± 0.2. The SS cells were only observed in the caudal stomach, with numerical density (QA [SS cells]/µm²) = 1.4x10^-2 ± 0.9 In I. iguana, variation was observed in terms of the distribution of mucus secretions and the pattern of occurrence of serotonin and somatostatin-secreting enteroendocrine cells in the TGI, which possibly will result in an interspecific adaptive response.

Keywords:  serotonin; somatostatin; stomach-oesophagus; morphology; reptilian