Gonadotropins I and II in juvenile coho salmon.
The present study was designed to obtain basic endocrine information on GTH I and GTH II in previtellogenic and prespermatogenic coho salmon (immature). Levels of GTH II in pituitary extracts were 6.5 ± 2.0 and 6.7 ± 2.0 pg/μg pituitary protein in male and female fish, respectively. In contrast, the pituitary content of GTH I was approximately 100-fold higher than GTH II (1.302 ± .22 and 1.173 ± .21 ng/μg pituitary protein in male and female fish, respectively). Plasma levels of GTH II in immature salmon were not detectable by RIA whereas plasma GTH I levels were approximately 0.62 ± 0.12 and 0.78 ± 0.13 ng/ml in male and female fish, respectively. Highly purified coho salmon GTH I and GTH II stimulated testicular testosterone production and ovarian estradiol productionin vitro in a similar manner, though GTH II appeared more potent than GTH I. Therefore, it appears that although the salmon pituitary contains predominantly GTH I prior to puberty, the gonad can respond to both GTH I and GTH II.
School of Fisheries, Univ. of Washington, Seattle, WA, 98195, U.S.A..
P
P
Swanson
M
M
Bernard
M
M
Nozaki
K
K
Suzuki
H
H
Kawauchi
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Dickhoff