Abstract
The incorporation patterns of [14C]adenine ([14C]A) and, as control, [3H]thymidine ([3H]TdR) by proliferative cells in the intestinal mucosa of rats and mice were studied by the autoradiographic technique. The animals received 3 daily, subcutaneous injections of the isotopic markers (1μCi/g body weight each) and examinations were made 3hr after the last injection.
The most striking finding was a strong labeling with [14C]A of a portion of non-lymphoid lamina propria cells (LPC) in the core of jejunal villi, in contrast to weak labeling of the epithelial cells with this isotopic marker. Furthermore, the labeling of epithelial cells decreased in intensity to a large extent following RNase treatment. In contrast, the silver grains over the LPC did not markedly decrease in number after RNase treatment and the cells still remained heavily labeled. Following extraction of DNA with DNase treatment, the heavy labeling of LPC vanished completely. This provides evidence for the incorporation of [14C]A into DNA of the LPC to a great extent.
The overall patterns of [3H]TdR labeling of mucosal cells, on the other hand, was characterized by fairly uniform labeling of proliferative cells and no great difference in the labeling intensity was recognized between the epithelial cells and the LPC of jejunal villi.
The results mentioned above were discussed in relation to the peculiar adenine metabolism of the LPC. It was suggested that the LPC have a limited capacity for de novo adenine synthesis and because of this they were labeled with [14C]A to a greater degree.
The LPC which exhibited heaviest labeling with [14C]A had the same morphological characteristics as those of the primitive reticular (or reticulum) cells, which have been described by Maximow (9) and Marshall (8) as undifferentiated mesenchymal cells. The similarity of the former cells to the latter cells was discussed.
