EFFECTS OF VARIOUS REPRODUCTIVE HORMONES ON THE PENETRATION OF LHRH ACROSS THE BLOOD-BRAIN-BARRIER

A previous study has shown bidirectional saturable transport of LHRH across the blood-brain barrier. Here, the effects of the steroids progesterone and beta-estradiol and the pituitary glycoproteins luteinizing hormone (LH) and follicle stimulating hormone (FSH) on the bidirectional transport rate were determined. No statistically significant difference in brain to blood transport of I-125-LHRH was found in mice given ICV progesterone (1 and 100 pmol/mouse), beta-estradiol (1 and 100 pmol/mouse), FSH (10 and 1000 pmol/mouse) or LH (100 and 1000 pmol/mouse). Blood to brain transport of I-125-LHRH, tested in rats with a carotid artery perfusion method, was not affected by inclusion of progesterone (100 nmol/ml), beta-estradiol (100 nmol/ml), LH (2 and 10 nmol/ml), or FSH (10 nmol/ml) in the perfusate. We conclude, therefore, that unlike its release from the hypothalamus, the exchange of LHRH between the CNS and blood is unlikely to be influenced by reproductive hormones.