PANCREATIC ISLETS OF REGENERATING PANCREAS AFTER CHRONIC ADMINISTRATION OF THYROXINE

Abstract

Objective - to characterize some parameters of the endocrine epithelium of the in a part pancreas remote from the site of resection during chronic administration of thyroxine. Materials and Methods. The experiment was conducted on 163 Wistar male rats. Fifty-six animals from the experimental group after partial pancreatectomy were given daily subcutaneous injections of dl-thyroxin (Reanal, Hungary) at a dose of 0,001 μg/g of BW. The part of the pancreas remote from the site of partial resection was analyzed morphometrically (weight of the head and body of the gland, total islet volume, B/A-cell islet volume ratios, sizes of nuclei and cells), autoradiographically (3H-thymidine), cytospectrophotometrically (amount of cytoplasmic RNA), and by electron microscopy. Results. After 30 days of experiment, the weight of the residual pancreas and the volume of islet tissue in it increased. The capillarization of pancreatic islets (PI) increased dramatically. B/A-cell volume ratio changed due to an increase in the proportion of the B-cell component. The incorporation of 3H-thymidine into the PO cells nuclei was reduced at the early stages of observation and returned to the control levels by the end of the observation period. During the experiment the ultrastructural characteristics of islet cells in animals of the experimental group changed from predominating on the 15th day «dark B-cells II» (actively synthesizing, containing a large number of secretory granules, with extensive spaces occupied by a Golgi apparatus, with a large number of ribbon-like «tightly conjugated» mitochondria) to «light B-cells I» (with expanded perinuclear spaces, expanded membranes of the granular cytoplasmic reticulum, well-pronounced Golgi apparatus with maturing secretory granules in its cisterns), prevalent after 30 days of experience. At all periods of observation, insulin cells demonstrated active endo-and paracrine secretion. In conditions of hyperthyroidism, the core of many secretory B-granules had the mulberry-like appearance both in the control and in the experiment. Conclusions. Thyroid hormones can become an important factor in the repair of pancreatic epithelium.

Keywords

pancreatic islets / reparative regeneration / hyperthyroidism / autoradiography / ultrastructure

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Utekhin V.I., Fedotkina T.V., Churilov L.P.