Summary
Comparative in vitro studies on the release of LH and FSH by pituitary-hypothalamus complex (PHC) with
intact portal plexus and whole pituitary (PI) from adult male rats showed that PHC
released LH at a greater rate and in larger amounts than PI. PHC and PI released FSH
in comparable amounts and rates. Attempts were made to correlate serum gonadotropin
levels to that released by PHC and PI at 1, 3, 7, 14, 21 and 46 days of post-castration
(PC). Sham operated animals served as controls. Castration increased serum LH and
FSH levels but in different profiles. CPHC and CPI (PHC and PI from castrated rats)
released less LH than NPHC and NPI (PHC and PI from sham operated controls) till day
14 PC after which CPHC and CPI released more LH than NPHC and NPI respectively. Castration
abolished the intrinsic capacity of PHC to secrete more LH than PI. CPHC and CPI secreted
significantly less FSH than NPHC and NPI at 1, 3 and 7 days PC. At days 14 and 21
of post-castration PCNCP or CPI and NPHC or NPI released similar amounts of FSH. Administration
of 5 α-dihydrotestosterone (DHT, 1 mg/rat/day) or estradiol valerate (EV, 1 μg/rat/day)
immediately following castration prevented the rise in serum LH and FSH but increased
the amounts of LH and FSH released by CPHC and CPI. The treatment caused a marked
stimulation of FSH released by CPI. DHT or EV administered from day 41 to day 46 PC
reduced the circulating levels of LH and FSH but markedly stimulated the release of
gonadotropins by CPHC and CPI. It is suggested that discretely separate mechanisms
control the release of LH and FSH by the pituitary.
Key-Words:
Castration
-
Pituitary
-
Hypothalamus
-
In Vitro
-
LH
-
FSH
