[SEASONAL DIFFERENCES IN THE EFFECT OF MELATONIN ON THE MORPHO-FUNCTIONAL STATE OF THE THYROID GLAND SPONTANEOUSLY HYPERTENSIVE RATS].

Abstract

We studied the effect of exogenous melatonin on the indicators of thyroid gland condition of the young spontaneously hypertensive rats in spring and autumn. These data suggested that after 28-day of melatonin administration (5 mg/kg) in different seasons of the year there were divergent effects on the state of the thyroid gland. So, melatonin increased synthetic activity of the gland in the spring. It was indicated by a reduction in the area of the follicular colloid, the inner diameter of the follicles, the number of connective tissue elements, increasing the height of thyrocytes, follicular colloidal index and reduced index accumulation colloid. Spontaneously hypertensive rats were less sensitive to the effects of melatonin in autumn. A significant increase in the number of the connective tissue elements, reduction of the follicular epithelium area and follicular colloidal index showed a decline in the functional activity of the thyroid gland after of melatonin administration in the autumn.