ABSTRACT
The effects of feeding inorganic tin on the gastrointestinal tract were examined in rats. Three groups of male weanling Wistar rats were fed a diet to which 0, 250, or 500 ppm Sn2+ had been added as SnCl2. A fourth group was subjected to feed restriction by pair feeding with the 500-ppm group. Comparison of the data from the tin-fed groups with both the control and the reduced diet groups allowed discrimination between effects of reduced feed intake and Sn2+ effects. Independent of the reduced feed intake, Sn2+ affected hemoglobin concentration in the blood and several small intestine parameters. Total length of the small intestine, as well as absolute and relative weights, was increased. An increase was also observed in the migration of epithelial cells along the villus, as revealed by [3H]thymidine incorporation and autoradiography in rats fed 900 ppm Sn2+ for 4 weeks. Stereo-light microscopy and scanning electron microscopy revealed the formation of ridge-like villi due to Sn2+ feeding and a decreased number of villi per unit surface. These data suggest that an increase in cell turnover in the small intestine, due to Sn2+, was responsible for these changes.
Subject(s)
Digestive System/drug effects , Tin Compounds , Tin/toxicity , Animals , Body Weight/drug effects , Cell Cycle/drug effects , Diet , Digestive System/anatomy & histology , Hemoglobins/metabolism , Intestine, Small/anatomy & histology , Intestine, Small/drug effects , Male , Microscopy/methods , Microscopy, Electron, Scanning , Organ Size/drug effects , Rats , Rats, Inbred StrainsABSTRACT
The pancreatic endocrine cells of Barbus conchonius are concentrated in a large (principal) islet, located near the gall bladder, and in a number of smaller islets. Five types of endocrine cells can be distinguished in there pancreatic islets: B cells, A1 (or D cells), 2 types of A2 cells (A2r cells with round granules; and A2fl cells with flocculent granules) and a scarce 5th cell type. The hormones produced by B and A2fl cells are probably insulin and glucagon respectively. The A2r cell contains granules with the same diameter as the granules of the enteroendocrine type III cell of the gut. Both cell types may resemble the enteroglucagon-producing EG cell of mammals. The function of the A1 cells, which are frequently found without secretory granules, and of the 5th cell type, will be discussed. The pancreastic islets of B. conchonius are strongly innervated, which suggests thatpresence of a direct nervous control system. Some intermediate or mixed cells containing exocrine and endocrine A2r granules are found continguous with the principal islet. The origin of pancreatic endocrine cells is also the subject of discussion.
