Variations in hepatic estradiol-17beta receptor concentrations during the annual reproductive cycle of diploid and triploid female catfish, Heteropneustes fossilis (Bloch).
Concentrations of hepatic estradiol-17beta (E2) receptors (ER) in cytosolic and nuclear fractions were evaluated in diploid and triploid female catfish Heteropneustes fossilis (Bloch) during four different reproductive periods of a complete reproductive cycle. Basal level of ER concentration was noted in the resting period of both diploids and triploids. Receptor level gradually elevated through the preparatory period and reached a peak in the pre-spawning period in both diploids and triploids. However, ER concentrations were overall reduced in triploid to that of diploid females. In a single point assay, in diploids, ER concentration showed about a 3-fold rise (p<0.001) in the cytosolic and a 4-fold rise (p<0.001) in the nuclear extracts from resting to the pre-spawning period. In triploids, only a 2-fold rise was observed both in cytosolic (p<0.01) and nuclear (p<0.05) ER concentration during the same span. Finally, a sudden fall of receptor level was observed in the spawning period in both the ploidy groups with a lower concentration in the triploids. The K(d) value did not differ between the females of diploids (cytosolic 1.12+/-0.21 nM and nuclear 6.9+/-0.9 nM) and triploids (cytosolic--1.13+/-0.17 nM, nuclear--6.8+/-2 nM). However, B(max) of the diploid showed about double the value than triploid females both in the cytosolic (diploid--367.4+/-33.24 pmol/mg protein, triploid--187.3+/-13.20 pmol/mg protein, p<0.001) and nuclear extracts (diploid--946+/-66 pmol/mg DNA, triploid-558+/-98 pmol/mg DNA, p<0.01) of liver. Lower E2 binding capacity and lower amount of E2 receptors of triploid catfish liver with a stunted vitellogenic status could be one of the major causes for reduced gonadal development and sterility in female triploids.
Biswas
Angshuman
A
Department of Animal Physiology, Bose Institute, Kolkata 700054, India.
Roy
Sumedha
S
De
Jhuma
J
Kundu
Samita
S
Pramanik
Mitali
M
Ray
Arun K
AK
D000818:Animals; D002397:Catfishes / Q000235:genetics / Q000254:growth & development*; D002467:Cell Nucleus / Q000737:chemistry; D003600:Cytosol / Q000737:chemistry; D004171:Diploidy; D004958:Estradiol / Q000032:analysis / Q000378:metabolism*; D005260:Female; D008099:Liver / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D011123:Polyploidy; D011959:Receptors, Estradiol / Q000032:analysis / Q000378:metabolism*; D012098:Reproduction
D011959:Receptors, Estradiol; D004958:Estradiol