Thyroid hormone-induced protein (TIP) gene expression by 3,5,3(')-triiodothyronine in the ovarian follicle of perch (Anabas testudineus, Bloch): modulation of 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4)-isomerase enzyme by TIP

Novel 3beta-hydroxysteroid dehydrogenases from gonads of the Nile tilapia: phylogenetic significance and expression during reproductive cycle

Multiple forms of 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD) and their differential tissue expression pattern have not been shown in any lower vertebrates. In the present study, we report cloning of two novel 3beta-HSDs and two variants from gonads of the Nile tilapia. 3beta-HSD cDNAs encode two peptides of 375 (3beta-HSD type-I/variant 1) and 367 (3beta-HSD type-II/variant 1) amino acid residues that share 31.9% homology. 3beta-HSD type-I/variant 1 shared high homology with other piscine counterparts while 3beta-HSD type-II/variant 1 exhibited homology to mammalian DeltaC27-3beta-HSD and multifunctional viral 3beta-HSD. The latter seems to be ancient form among vertebrates. Transiently transfected 3beta-HSDs' open reading frames in COS-7 cells converted exogenous pregnenolone/androsta-5-ene-3beta-17beta-diol to progesterone/testosterone. Tissue distribution pattern of 3beta-HSDs by RT-PCR revealed varied expression pattern. Northern blot analysis of 3beta-HSDs demonstrated steady or gradual rise in transcripts level at different gonadal stages. These data revealed the importance of novel 3beta-HSDs in teleosts and also provided phylogenetic significance.

Habitat-related variation in reproductive endocrine condition in the coral reef damselfish Acanthochromis polyacanthus

Spiny damselfish Acanthochromis polyacanthus are brood protectors with no larval dispersal stage, with the result that characteristics of local populations are likely to reflect local habitat conditions. In order to assess the possible effect of habitat on reproductive characteristics, spiny damselfish were captured by divers in 1999 and 2001 from reefs around Lizard Island in the northern section of Australia's Great Barrier Reef, chosen to represent a range of coral cover characteristics. Fish were bled underwater immediately after capture, then blood and fish were placed on ice at the end of the dive for transport to the laboratory where plasma was separated for subsequent measurement of testosterone (T) and 11-ketotestosterone (11KT) in males, and T and 17beta-estradiol (E2) in females. Ovaries from fish captured in 2001 were dispersed to isolate vitellogenic follicles, fecundity and follicle size were determined, then follicles were incubated in Leibowitz L15 medium alone or with human chorionic gonadotropin (hCG), to assess steroidogenic capacity. In 1999 there were significant site to site variations in plasma T and E2 levels in females, and in 2001, in E2 in females, and in T and 11KT in males. Highest hormone levels were recorded from sites of both low and high coral cover (a measure of presumptive habitat quality), but there was consistently low steroid production in fish from a site of high coral cover and fish density. An initial expectation that poor reproductive condition might be associated with degraded coral sites was not met. Vitellogenic follicles from fish captured in 2001 showed increased in vitro production of E2 and to a lesser extent, T, with increasing follicle size, and this was further augmented by treatment with hCG. Comparison of regression slopes of log E2 production versus follicle size showed that fish from sites where there were generally low levels of plasma steroids also had impaired in vitro steroidogenic capacity, and that this effect partially disappeared when follicles were stimulated with hCG. Reduced steroidogenic capacity was strongly associated with low fecundity, indicating that low in vitro and in vivo E2 production were reflected in reduced reproductive capacity. As the effect was most consistent at a site where fish density (and subsequent competition for planktonic food) was high, it is suggested that nutritional status associated with habitat characteristics may regulate reproductive endocrine condition in spiny damselfish. It is clear that local factors other than coral cover can generate site variation in reproductive performance.

Molecular cloning and characterization of 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase cDNAs from Japanese eel ovary

3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3beta-HSD) is a crucial steroidogenic enzyme which catalyzes an essential step in the biosynthesis of all classes of steroid hormones. Two closely related cDNAs, encoding Japanese eel ovarian types I and II 3beta-HSD, were cloned and characterized. Both cDNAs putatively encoded 375 amino acid residues sharing high sequence homology with those of rainbow trout (71%) and mammalian (approximately 45-50%) 3beta-HSD. Transient expression of types I and II 3beta-HSD in COS-7 cells revealed that both proteins possess 3beta-hydroxysteroid dehydrogenase as well as Delta(5)-Delta(4) isomerase activity for both pregnenolone and dehydroepiandrosterone, with the preference of pregnenolone over dehydroepiandrosterone as substrate, although the type I protein is more active than the type II. By northern blot analysis, a single band of the 3beta-HSD transcript of approximately 1.5kb in length was observed in ovarian tissue and the total transcript abundance of both 3beta-HSDs remained constant throughout ovarian development artificially induced by gonadotropin-rich salmon pituitary homogenate. This lack of change in 3beta-HSD transcript abundance during ovarian development did not correlate with the fluctuation of its enzymatic activity reported previously, which may suggest that changes in 3beta-HSD activity during ovarian development may be, in part, post-transcriptionally regulated in the Japanese eel ovary.