Gonadal regulation of gonadotropin secretion in male monkeys

Abstract

The gonadotropin re leas ing hormone (GnRH) is though t to cont rol both pituitary FSH and LH sy nth esis and sec re tion. As the go nads res pond to FSH and LJ-I during the prepubertal and adult periods subtle feed back signals f rom the tes tis or ovaries are tran sduced by the cen tral ne rvous sys tem a nd/or the pitui tary to reg ul :lIe spermatogenesis and ovarian folli c le turnover. Aim of this thesis was to study the acute e ffects of tes tostero ne on FSI-I and LI-I sec ret ion in go na cl:llly intac t and long- term orc hidectom ized adult monkeys, and to in ves t igate: - the poss ible e f fec t of testos te rone on go nadotrop in reg ulation at the pi tuitary or the hypo thalamic level. - the possibi li ty of causing a re lease of go nadotropi ns through Gn Rl1 stilll ul:ltion in animals und er tes tostero ne t reatme nt. - d iffe re nces in the bioacti vity and immunoreac tivity of Lli under tes tos te rone trealment and to inves ti gate the phys iological significa nce of gonadal sec re t ions in the feedback regu lation of gonadotropins in adu lt ma le monk eys. Attempts have been made 10 control male ferti lity by hormonal or c hellli cal rn e:l IlS in volvi ng nega ti ve feedback suppress ion of pituit:lry go n:ldotropin sec reti on by tes tostero ne. On the ba sis of chemical similarities be tween go n:ldo t ro pi ns of non human and hUnl:ln primates, and re lated morphology of Ihe cell types from which they :lre secre ted mo nkeys wcre used in these studies as a model to Study patt e rns or c ircul:l ting go nado tropins which ma intai n reproduction in the mature male prirn:lIe. GnRH stimul:l tion tests wcre performed to assess the poss ible s ite of ac tion of tes tostero ne i.e. at the hypot ha lamic or pilUil3. ry level ane! in vivo modulat ion of pitui tary GnR H rece ptors unde r tes toste rone nnc! GnRl1 :ln ta go nist Ircannell!.