MORPHO-FUNCTIONAL CHANGES IN SMALL INTESTINE EPITHELIUM OF FROG <i>RANA TEMPORARIA </i>DURING HIBERNATION
Structure and function of small intestinal epithelium were studied in overwintering frogs <i>Rana temporaria </i>at various stages of hibernation. In the process of testing of absorption of arginine vasotocin (AVT) in experiments <i>in vitro </i>it is established that at the period of hibernation there is preserved the capability of the epithelium for absorption of this nonapeptide without hydrolysis. However, as compared with October-December, in January-February and later, a decrease of the AVT absorption takes place, which is the most pronounced in March-April. Changes in epithelial structures appear by the middle of winter and are progressing by spring. In April-May, as compared with the beginning of hibernation, the height of enterocytes, the length of microvilli, and the number of microvilli decrease by 33 %, 40 %, and 57 %, respectively. The absence of features of destruction indicates an adaptive character of the observed changes. Dynamics of the studied parameters indicates morphological plasticity of the small intestine epithelium of <i>R. temporaria </i>at the period of hibernation.