Ultrastructural evaluation of the radioprotective effect of sodium selenite on submandibular glands in rats

Abstract

The aim of this study was to evaluate the radioprotector effect of sodium selenite on the ultrastructure of submandibular glands in rats. Fifty-seven male albino Wistar rats were randomized to 4 groups: control, irradiated, sodium selenite and irradiated/sodium selenite. The animals in the sodium selenite and irradiated/sodium selenite groups received intraperitoneal injections of sodium selenite (0.5 mg/kg body weight) 24 h before irradiation. The animals belonging to the irradiated and irradiated/sodium selenite groups were submitted to 15 Gy of gamma radiation in the head and neck region. The submandibular glands were removed at 4, 8, 12, 24, 48 and 72 h after irradiation. The ionizing radiation induced damage to the secretory cells, especially the serous cells, right from the first period. Vacuolization, lysis of cytoplasmic inclusions and nuclear alterations occurred. The sodium selenite group also presented cellular alterations in the study periods, but with less damage compared to that caused by radiation. There was greater similarity between the irradiated/sodium selenite group and the control group than with the other groups treated in all study periods. Despite the alterations observed in the sodium selenite group, sodium selenite presented a radioprotective action on the secretory cells of submandibular glands.

FIGURE 1. Transmission electron microscopy of the control group and irradiated submandibular salivary gland tissue 4 h after gamma ray irradiation. (A) Control group: convoluted granular tubules with serous cells presented secretion granules (white arrow). (B) Irradiated group: convoluted granular tubules with serous cells presented serous secretion granules with bonds (white arrow) and decreased electrodensity of contents (black arrow). (C) Control group: mucous cell presented mitochondria (black arrow), secretion granules (SG), nuclei (N) and rough endoplasmatic reticulum (white arrow). (D) Irradiated group: acini with mucous cells presented fibril-like condensations (arrow) in mucous granules. (E) Control group: serous cell presented nuclei (N) and secretion granules (SG). (F) Control group: serous cell presented nuclei (N), rough endoplasmatic reticulum (white arrow) and Golgi complex (black arrow). (G) Irradiated group: pleomorphic nucleus with thickened membrane (black arrow) and chromatin condensation, surrounded by degenerated organelle (white arrow) and free polyribosomes. (H) Irradiated group: vacuoles with varying content of nucleus and cytoplasm (arrow).

FIGURE 2. Transmission electron microscopy of submandibular gland tissues for each groups at 4 h. (A) Mucous cells from the irradiated group. (B) Serous cells from the irradiated group presenting greater degranulation than the mucous cells. (C) Serous cells from the sodium selenite group. (D) Serous cells from the sodium selenite/irradiated group.

FIGURE 3. (A) Serous cells from the irradiated group 12 h (A,B) and 24 h (C,D) after irradiation. (B) Serous cells from the sodium selenite group at 12 h. (C) Serous cells from the sodium selenite/irradiated group at 12 h. (D) Serous cells from the irradiated group at 24 h. (E) Serous cells from the sodium selenite group at 24 h. (F) Serous cells from the sodium selenite/irradiated group at 24 h.

FIGURE 4. (A) Serous cells from the irradiated group at 72 h after irradiation. (B) Serous cells from the sodium selenite group at 72 h. (C) Serous cells from the sodium selenite/irradiated group at 72 h. (D) Serous cells from the control group.