Regulation of ovarian hyperluteinization.

Adult female rats with neonatally damaged posterior hypothalamus, made by a transversal cut, were investigated. Plasma levels of prolactin (PRL), gonadotropic hormones (GTH) and female gonadal steroids (GS) were determined by radioimmunoassay. The animals were sacrificed, at the ages of 4 and 6 months and their hypothalamus, pituitary gland, ovary and uterus were examined using light microscopy. The results can be summarized as follows: body mass of animals, with damaged posterior hypothalamus, was significantly reduced. Masses of luteinized ovaries were increased and uterine tissues decreased. Serum levels of PRL were significantly increased and luteinizing hormone (LH) decreased. Ultrastructural changes in the corpora lutea (CL), previously described, showed clear signs of their reduced capacities to produce GS, both estradiol (Oe) and progesterone (Pg) per total ovarian mass. However, prostaglandin 2 alfa (PGF2alpha) known as a luteolytic factor, was also diminished in the evidently retarded endometrium. As a result of decreased plasma values of LH, Pg and PGF2 alpha, luteolysis of CL in hyperluteinized ovaries did not occur, and their new generations were accumulated during subsequent cycles. The character of interruption and recovery of aminergic and peptidergic neurons, involved in regulation of hypothalamic-pituitary gonadal axis and feed-back effects of steroid hormones, require further studies.

The effects of continuous light and darkness on the activity of monoamine oxidase A and B in the hypothalamus, ovaries and uterus of rats.

For assessing monoamine oxidase (MAO-A and -B) activities in the hypothalamus, ovaries and uterus, mature female rats were exposed to either continuous light or dark over 6 weeks. Confirming previous studies, continuous light induced constant estrus in all animals. The majority of animals kept under continuous dark during the six weeks remained mostly in diestrus with estrus appearing sporadically. The endocrinological function of the ovaries was disturbed by continuous light, which resulted in the development of polycystic ovaries, their morphological appearance being not significantly affected by continuous dark. Hypothalamic MAO-A activity was markedly reduced under the influence of both light (p < 0.05) and dark (p < 0.01). The activity of hypothalamic MAO-B was reduced only under the influence of dark (p < 0.01). In the ovaries, no significant differences were detected in either MAO-A or -B activity as a result of these environmental manipulations. In the uterus of rats exposed to continuous light which developed polycystic ovaries, MAO-A activity was significantly lower (p < 0.05) in comparison to either intact controls or rats exposed to continuous dark. These results demonstrate that chronic changes in photoperiodicity may considerably influence MAO-A activity and to a lesser extent MAO-B activity dependent on the tissue studied.

Basal and stress induced concentrations of adrenal gland catecholamines and plasma ACTH during aging.

Basal and stress levels of catecholamines (CA) in the adrenal glands, and circulatory levels of adrenocorticotropic hormone (ACTH) were examined in female Wistar rats aged 1, 3, 10 and 24 months. Our data showed reduction in basal dopamine (DA) concentration in adrenal glands and an increase in this catecholamine in response to stress at all ages (1, 3, 10, 24 months). The greatest levels of basal norepinephrine (NE) and epinephrine (E) concentrations in the adrenal glands were noted in intact rats at the age of 24 months. On the other hand, the stress response of NE and DA had a tendency to fall, reaching basal values at the age of 10 and 24 months of age. Basal circulatory levels of ACTH showed a reduction with age. The stress response of ACTH was reduced in animals aged 10 and 24 months. Reduced basal values of adrenal DA and increased NE and E values, suggest that there is increased adrenomedullar activity at the age of 24 months. On the other hand, the reduced or even absent stress response of NE and E observed in the adrenals, in 10 and 24 months old rats, may be of interest in considering the ability of these animals for adaptation. Basal and stress values of plasma ACTH are significantly reduced with the onset of senescence in female rats.

The effect of constant light on the concentration of catecholamines of the hypothalamus and adrenal glands, circulatory hadrenocorticotropin hormone and progesterone.

The participation of adrenocorticotropic hormone (ACTH) in the control of adrenal glands and the regulation of ACTH secretion in female rats exposed to constant light for six weeks were studied. A significant increase of plasma ACTH (p < 0.05) in rats exposed to constant light is in correlation with an increase of epinephrine (E) synthesis in adrenal gland (p < 0.05) when compared to intact controls. On the other hand, ACTH secretion is in inverse relation with a significantly reduced concentration of dopamine (DA) and norepinephrine (NE) in hypothalamus (p < 0.05). In addition, higher concentration of plasma ACTH in rats exposed to constant light through its effect on the adrenal cortex is responsible for the appearance of polycystic ovaries. As a contribution to this assumption is the result showing an increased concentration of serum progesterone in rats exposed to constant light when compared to corresponding controls which is probably of adrenal origin. These results indicate an inverse relationship between plasma ACTH concentrations and DA and NE concentrations in hypothalamus and that the hypothalamo-pituitary-adrenal axis has a significant role in the regulation of ovarian function.