Seasonal patterns of basal and GnRH-induced LH, FSH and testosterone secretion in Eld's deer stags (Cervus eldi thamin).
Plasma LH, FSH and testosterone were measured in blood samples collected via remote catheterization from six adult Eld's deer stags every 10 min for 8 h before and 2 h after GnRH (1 microgram kg-1, i.v.) administration. Blood samples were collected within 2 weeks of the summer solstice (21 June), autumn equinox (22 September), winter solstice (21 December) and spring equinox (20 March). Marked seasonal variations in basal LH, FSH and testosterone concentrations were observed. From autumn, well-defined LH pulses were temporally associated with small, but detectable pulses in testosterone. During the winter transition into the breeding season, episodic LH pulses were also temporally associated with corresponding testosterone surges that lasted 2-3 h. High amplitude, low frequency testosterone surges were also observed during the spring, but often in the absence of detectable LH pulses. Basal LH and testosterone concentrations decreased during the summer and, although LH pulses were detected, associated testosterone pulses were absent. Only 37% of LH pulses occurred coincidentally with FSH pulses, and FSH pulses were generally less prominent. The increases in LH and FSH above basal concentrations after GnRH treatment were significant (P < 0.05) for all seasons. Increases in testosterone after GnRH treatment were greatest during the winter and spring, but testosterone also increased to a lesser extent during the autumn (P < 0.05). In contrast, testosterone concentrations were not different before and after GnRH treatment during summer.(ABSTRACT TRUNCATED AT 250 WORDS)
Monfort
S L
SL
Department of Animal Health, Smithsonian Institution, Front Royal, VA 22630.
Brown
J L
JL
Wood
T C
TC
Wemmer
C
C
Vargas
A
A
Williamson
L R
LR
Wildt
D E
DE
D000818:Animals; D003670:Deer / Q000097:blood / Q000502:physiology*; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects; D012621:Seasons; D012636:Secretory Rate / Q000502:physiology; D013739:Testosterone / Q000097:blood / Q000378:metabolism*
D006065:Gonadotropins, Pituitary; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone