Korfüggő glükó-, és mineralokortikod hatások vizsgálata vazopresszin hiányos Brattleboro patkányban

Abstract

Previously we proved that vasopressin takes place an age-related manner in the regulation of the hormone levels of the hypothalamo-pituitary-adrenal axis. The effector molecules of the axis are glucocorticoids, which are structurally very similar to mineralocorticoids, and they can act on the same receptors. Therefore the aim of our present work was to examine the agerelated influence of vasopressin on gluco- and mineralocorticoid levels and their receptors. Perinatal (10 days old) and adult (10 weeks old) male rats were used. We compared vasopressin deficient Brattleboro rats to their heterozygote littermates. Corticosterone (glucocorticoid) and aldosterone (mineralocorticoid) levels were measured by radioimmunoassay under resting conditions and after hypoglycemic stress. Gluco- (GR) and mineralocorticoid receptor (MR) mRNA levels were measured by quantitative PCR in the hypothalamus and liver. Independetly from the genotype the smaller rats showed only minimal corticosterone increase to stress, while their aldosterone elevation was more expressed compared both to adults and to corticosterone levels. The level of GR and MR mRNA were smaller in the hypothalamus and liver of 10 days old rats. In 10 days old vasopressin deficient rats the corticosterone levels were higher, while their GR and MR mRNA levels were lower in the liver (weeker effect) and higher in the hypothalamus (stronger feedback) compared to heterozygous animals. Our results supports the existence of stress hyporesponsive period, while 10 days old rats showed smaller glucocorticoid elevations with lower receptor levels compared to adult. The opposite (stress hyperresposibility) was true for the pups' aldosterone levels. In general the consequences of vasopressin deficiency was more pronounced in 10 days old animals supporting the view that vasopressin plays a more considerable regulatory role in the perinatal age.