title: Starvation-induced suppression of pituitary-testicular function in rats is reversed by pulsatile gonadotropin-releasing hormone substitution.
abstract: This study was carried out to test the hypothesis that reduced hypothalamic GnRH release is responsible for the suppression of reproductive functions during starvation. Adult male rats were kept for 4 days under total fasting (only water allowed) and injected during this time at 2-h intervals with 100 or 500 ng/kg BW of GnRH or vehicle. Serum levels of LH and FSH decreased by 30% during starvation (p less than 0.05), and these effects were fully reversed by either dose of GnRH treatment. Starvation reduced the pituitary mRNA contents of the gonadotropin common alpha- and FSH beta-subunits by 30% and 35% in starved animals (p less than 0.05 for both), but the LH beta-subunit mRNA was unaffected. The GnRH treatments partly or totally reversed these changes, but up-regulation of the mRNA levels by GnRH was seen only in controls fed ad libitum. Starvation reduced the testicular and serum levels of testosterone by 84% (p less than 0.01) and 42% (p less than 0.05), respectively. These changes were fully reversed by the 500-ng/kg dose of GnRH treatment during fasting, but only serum T was completely reversed by the 100-ng/kg GnRH treatment. To elucidate whether fasting per se had direct effects at the gonadal level, we blocked the secretion of gonadotropins by treatment with a GnRH antagonist, and replaced the gonadotropins by injecting of hCG (10 IU/kg BW once daily) and hFSH (75 IU/kg BW once daily). No differences were observed between starved and control animals in either testicular or serum levels of T, or in accessory sex gland weights.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology, University of Turku, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Bergendahl
authors.forename: A
authors.initials: A
authors.lastname: Perheentupa
authors.forename: I
authors.initials: I
authors.lastname: Huhtaniemi
mesh_terms: D000818:Animals; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage* / Q000378:metabolism; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012098:Reproduction / Q000187:drug effects / Q000502:physiology; D013217:Starvation / Q000503:physiopathology*; D013737:Testis / Q000187:drug effects / Q000502:physiology*
chemical_list: D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone