Vol. 279, Issue 2, R389-R393, August 2000
Effect of 17
-estradiol on the expression of
somatostatin genes in rainbow trout (Oncorhynchus
mykiss)
Alison C.
Holloway1,
Gregory T.
Melroe2,
Melissa
M.
Ehrman2,
P. Konda
Reddy1,
John F.
Leatherland1, and
Mark A.
Sheridan2
1 Department of Biomedical Sciences, Ontario Veterinary
College, University of Guelph, Guelph, Ontario N1G 2W1, Canada; and
2 Department of Zoology and Regulatory Biosciences Center,
North Dakota State University, Fargo, North Dakota 58105
In the present
study, the effects of 17
-estradiol (E2) treatment on the
expression of preprosomatostatin (PPSS) I, PPSS II', and PPSS II" mRNA
in the hypothalamus and endocrine pancreas (Brockmann body), as well as
the effects of E2 treatment on plasma somatostatin (SS)-14
and -25 concentrations in sexually immature rainbow trout
(Oncorhynchus mykiss), were investigated. E2
treatment significantly (P < 0.001) depressed both
plasma SS-14 and SS-25. In the hypothalamus, E2 treatment
significantly (P < 0.001) decreased the levels of PPSS
I and PPSS II" mRNA. However, there was no effect of E2
treatment on PPSS II' mRNA levels. In the pancreas, E2
treatment had no significant effect on the levels of either PPSS II'
mRNA or PPSS II" mRNA. However, E2 treatment significantly (P < 0.005) decreased levels of PPSS I mRNA. These
data suggest that E2 acts, in part, to increase plasma
growth hormone levels in rainbow trout by decreasing the endogenous
inhibitory somatostatinergic tone by inhibiting plasma levels of both
SS-14 and SS-25 and hypothalamic levels of mRNA encoding these proteins.
differential gene regulation
