Differences in seasonal expression of neurohypophysial hormone genes in ordinary and precocious male masu salmon.
Our previous study showed the seasonal variations in expression of vasotocin (VT) and isotocin (IT) genes in preoptic magnocellular neurons of female masu salmon (Oncorhynchus masou). The changes in the level of VT mRNA were coincident with those in plasma testosterone and estradiol levels. In the present study, generality of this phenomenon in salmonid was verified in males. We examined changes in expression of VT and IT genes by an in situ hybridization technique and an immunohistochemical avidin-biotin complex method in the preoptic nuclei of ordinary and precocious male masu salmon. Plasma levels of testosterone and estradiol were measured by enzyme immunoassay. Fish were sampled in March, May, August, and November 1994 and January 1995. The intensities of hybridization signals for VT and IT mRNAs, as well as immunoreactivity of VT and IT, showed seasonal variations, although the profiles were different between the ordinary and precocious males. In the ordinary males, the intensities of hybridization signals for VT and IT mRNAs were high in January. These strong hybridization signals, representing elevation of VT and IT gene expression, were accompanied by increases in plasma levels of testosterone and estradiol. However, in precocious males, changes in VT and IT mRNA levels were not coincident with variation of plasma levels of sex steroid hormones. The sensitivity to sex steroid hormones of VT and IT gene expression may be different between the ordinary and precocious male masu salmon.
Ota
Y
Y
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Hokkaido, Sapporo, 060-0810, Japan.
Ando
H
H
Ueda
H
H
Urano
A
A
D000818:Animals; D001360:Avidin; D004958:Estradiol / Q000097:blood; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007231:Infant, Newborn; D008297:Male; D010121:Oxytocin / Q000031:analogs & derivatives* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D012474:Salmon / Q000378:metabolism*; D012621:Seasons; D013739:Testosterone / Q000097:blood; D014668:Vasotocin / Q000235:genetics*
D012333:RNA, Messenger; D001360:Avidin; D013739:Testosterone; D004958:Estradiol; D010121:Oxytocin; C008215:isotocin; D014668:Vasotocin