The distribution and frequency of endocrine cells in the splenic lobe of grass lizard (Takydromus wolteri): An immunohistochemical study

The regional distribution and frequency of the pancreatic endocrine cells in the splenic lobe of grass lizard, Takydromus wolteri, were studied by immunohistochemical (PAP) method using six types of specific mammalian antisera against bovine Sp-1/chromogranin (bCG), serotonin, insulin, glucagon, somatostatin and human pancreatic polypeptide (hPP). The pancreas was subdivided into two regions – islet kike and exocrine regions. The frequency of each immunoreactive (IR) endocrine cells was calculated as mean number/total 100 islet cells and as mean number/total 1000 cells (including exocrine and endocrine cells) using automated image analysis process. In addition, the percentage of each IR cell was also calculated. All of six endocrine cells were demonstrated. They were dispersed in the whole pancreatic parenchyma between exocrine acinar cells, or they were also observed as islet like clusters. In islet-like regions, bCG-, insulin- and glucagon-IR cells were detected as one or two cell layer cords and they were located between this cell-cords with 14.30±5.62, 61.50±9.76 and 26.50±9.31/100 cells frequencies, respectively. However, somatostatin-IR cells were mainly located in the peripheral parts not in cell-cords with 12.40±4.86/100 cells, and no serotonin- and hPP-IR cells were demonstrated. In exocrine regions, all of bCG-, serotonin-, insulin-, glucagon-, somatostatin- and hPP-IR cells were detected and they occurred mainly among the exocrine parenchyma as solitary cells with 10.30±2.54, 0.80±0.63, 15.50±5.30, 5.80±2.66, 3.10±1.29 and 11.00±3.33/1000 cells frequencies, respectively. In addition, serotonin-IR cells were mainly located between epithelia and connective tissue of pancreatic duct. Overall, there were 0.58±0.49% serotonin–, 56.44±9.35% insulin–, 23.73±8.22% glucagon–, 11.28±3.03% somatostatin– and 7.97±2.02% hPP-IR cells