Revyakina H. Hypophysis-thyroid system status and physiologic calorigenesis in white rats during acute exposure of cold.

It was revealed that exogenous epinephrine administration in conditions in situ increases the heat formation function of muscle of white rats due to energetic effectiveness decrease of contractility. This mechanism of thermogenic validity increase of muscle contraction is the most effective in physiologic cooling model and together with hypothermic condition development is gradually inactivated. It disappears totally in deep hypothermia. It was shown that regulation of thyroid hormones secretion does not yield to the law " plus - minus interaction" in thermoneutral zone conditions in physiologic fluctuations of serum thyrotropin. The regulation is carried out mainly by a principle of positive feedback. On the borders of physiological range of thyrotropin the negative feedback as a regulation principle in the system is activated. It was shown by means of parallel immunoenzyme and morphometric analysis that during increase of hypothermic exposure the activity of hypophysis-thyroid system undergoes appropriate phases: initial activation - hyperactivity - total oppression of secretion function.