PERMEABILITY OF THE BLOOD-BRAIN-BARRIER AND BLOOD-TESTIS BARRIER TO LH, FSH, AND ALBUMIN IN YOUNGER AND OLDER MICE

Reproductive and sexual function depends on an integration of the brai n, pituitary, and gonads that is mediated, in part, by humoral communi cation. We compared the ability of radioactively labeled LH and FSH to cross the blood-brain barrier (BBB) and the blood-testis barrier (BTB ) with that of radioactively labeled albumin, which is restricted by t hese barriers, in younger and older mice. For the BTB, entry rates wer e LH > FSH > albumin with no age difference or saturable transport. Fo r the BBB, LH, but not FSH, crossed faster than albumin and had a satu rable component that was more readily inhibited in older mice. The res ults show that entry into the brain, but not into the testis, of LH, b ut not of FSH, is saturable and changes with age.