SECRETORY RESPONSE OF PANCREATIC ACINI AND ISLETS OF LANGERHANS IN ALBINO RAT AFTER PILOCARPINE INJECTION (HISTOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY)
Aly A.M. Shaalan1, Khaled S.H. El- Mousalamy2 and Mohammed S.A. Khalifa2
Departments of Histology, Faculty of Medicine,1 Seuz Canal and 2Zagazig University
The cholinesters and muscarinic alkaloids stimulate secretion of glands that receive parasympathomimetic or sympathetic cholinergic innervation including pancreas, lacrimal and salivary glands. This study included ten adult albino rats aged about 3-5 months and weighed from 200-250 gm. They were divided into two groups, the control group which included five rats that received 1 ml. of 0.9% NaCl solution intraperitonealy (i.p). The treated group included five rats that received pilocarpine 4 mg/100 gm/body weight in 1 ml. of 0.9% NaCl solution (i.p). The animals were sacrificed after four hours of injection and pancreas was removed, parts of pancreas were fixed in 10% neutral buffered formol saline solution and processed for immunostaining. The other parts were fixed in 2.5% gluteraldehyde in phosphate buffer and then processed for light and transmission electron microscope examination. The pancreatic acini of treated group by light microscope examination showed that some cells still contain many granules while others degranulated or contained little granules. The connective tissue septa between lobes and lobules were infiltrated with mast cells. Also, islets of Langerhans showed infiltration with mast cells and the nuclei of islet cells were darker than that of control. By immunostaining, chromogranin A (CgA) in control group appeared brown in colour in most of islet cells, while, acinar cells appeared negatively stained. On the other hand, CgA granules appeared abundant in cells of islets of treated group. Ultrastructurally, the pancreatic acinar cells of treated group contained nuclei with irregular contour, extensive rough endoplasmic reticulum (rER) profile. Secretory granules of many cells were less electron-dense. Mitochondria became numerous and elongated. Islets of Langerhans of treated group examined by electron microscope showed some nuclei with cloudy chromatin and less prominent nucleoli while other nuclei were electron dense. The cytoplasm contained dilated cisternae of rER in some cells and vacuoles in others. Mitochondria appeared elongated and numerous in some cells. Granules appeared in all cells, these granules had central electron dense core varied in size and electron densities and surrounded by electron lucent halo that widened more than those of control. In conclusion, the use of pilocarpine and other cholinomimetic agents, especially for long time, must be put under strict precautions to prevent exhaustion of pancreatic acini and islets of Langerhans which may lead to other complications.