Effects of irradiation on intestinal cells in vivo and in vitro.

The effects of irradiation on intestinal epithelial cells were analyzed in vivo and in vitro. The in vivo study was carried out on the rat small intestine and for the in vitro study the intestinal crypt cell-line IEC-6 was used. Rat intestine and IEC-6 cells were irradiated with X-ray doses ranging between 1-16 Gy. Energy-dispersive X-ray microanalysis was used for detection of the elemental changes in the cells. Cell morphology was investigated in the scanning electron microscope, DNA-synthesis by autoradiography of 3H-thymidine incorporating nuclei and proliferation by cell counting. Our results indicate that in vivo, in the crypt cells, the increasing doses of irradiation led to increased sodium and lowered potassium and phosphorus concentrations. Corresponding ion shifts were found in the irradiated IEC-6 cells. Cells continued to proliferate up to the dose of 8 Gy, although the proliferation rate became lower with increasing dose of irradiation. The increasing dose of irradiation significantly reduced DNA-synthesis (16 Gy decreased DNA-synthesis by 50%) which resulted in a complete inhibition of cell proliferation. Analysis of goblet cells also showed characteristic radiation-dependent elemental changes. Scanning electron microscopical investigation of cells in culture revealed that most of the control cells were flat and had rather smooth cell membranes. Irradiation led to the appearance of numerous different membrane manifestations (microvilli of varying length and distribution, and blebs). Frequency of differences in the topology of the cells was related to the dose of irradiation. Our study clearly demonstrates that even low doses of irradiation cause changes in the ionic composition of the cells and inhibit DNA-synthesis and cell proliferation. The effects observed in the crypt cells in vivo were the same as in the intestinal cell line in vitro, which indicates that IEC-6 cells can be used for investigation of side effects of radiation to the abdomen.

Dose-time-dependent histological changes following irradiation of the small intestine of rats.

The distal ileum of 48 male Sprague-Dawley rats was exteriorized and irradiated either with low dosis (9-12 Gy, N = 18 rats), moderate dosis (15-18 Gy, N = 18 rats) or high dosis (21-24 Gy, N = 12 rats). A shielded segment of the ileum in the same animals as well as the sham-irradiated exteriorized ileum of 10 rats served as controls. The animals were allowed to survive for 3, 10, or 30 days. A total of 16 histologic parameters were found to be relevant for this study. Cell necrosis, loss of goblet cells, crypt abscesses, structural changes of the crypts, loss of Paneth cells, decreased number of mitoses, appearance of clear basal cells, loss of margination of lymphocytes, increased colagen in the submucosa, muscularis propria and subserosa, ectopic mucosal glands, as well as mucosal ulcerations, were found to be dose-time-dependent irradiation changes. Racket-shaped superficial epithelial cells, capillary congestion, and an increased number of round cells in the lamina propria mucosa were found to be time-dependent histological parameters. Preparations from the shielded ileum or from the sham-irradiated control animals showed normal histology. This study appears to be the first in which the systematic analysis of several postirradiation histologic changes have been found to be dose- and/or time-dependent. The knowledge that some radiation changes are dose-time-depeendent, whereas others are exclusively time-dependent, may open new vistas on the study of postradiation enteritis in the rat.

Distribution of sodium, magnesium, phosphorus, sulphur, chlorine, potassium, calcium and iodine in mammalian thyroid gland.

Anhydrous specimen preparation techniques and X-ray microanalysis were used to study the elemental composition of the rat thyroid follicular cells and colloid in the follicular lumen. Analysis were performed in morphologically defined follicular cells and adjacent colloid. Use of semithin cryosections allowed us to selectively analyze cell nucleus and dense vesicles in the cytoplasm of follicular cells. The analytical results indicate that the basolateral and apical cell membrane of follicular cells act differently in the transport of iodine and other ions, thus creating ionic gradient in the follicular lumen as compared to that found in the follicular cells. High potassium levels were found in the colloid. This finding indicates an active secretion of potassium from the apical plasma membrane into the follicular lumen. High sulphur and calcium levels were also found in the colloid. Dense vesicles found in the cytoplasm of follicular cells varied in size and had different elemental composition.