Changes in the Expression of Genes Encoding Steroidogenic Enzymes in the Channel Catfish (Ictalurus punctatus) Ovary Throughout a Reproductive Cycle

• Published in: Biology of reproduction Vol. 63; no. 6; pp. 1676 - 1682
• Main Authors: SAMPATH KUMAR, R, IJIRI, Shigeho, TRANT, John M
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01.12.2000
• Subjects: Animal aquaculture; Animal productions; Animals; Biological and medical sciences; Estradiol - metabolism; Female; Fundamental and applied biological sciences. Psychology; Ictaluridae - metabolism; Non mammalian vertebrate reproduction; Nuclease Protection Assays; Ovary - enzymology; Ovary - growth & development; Pisciculture; Reproduction - physiology; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; RNA, Messenger - isolation & purification; Seasons; Steroids - biosynthesis; Testosterone - metabolism; Vertebrate aquaculture; Vertebrates: reproduction; Breeding season; Androgen; Enzyme; Estrogen; 17β-Estradiol; Gene expression; Ictalurus punctatus; Ovarian hormone; Freshwater environment; Ovary; Testosterone; Vertebrata; Seasonal variation; Pisces; Animal; Female genital system; Steroidogenesis; Testicular hormone; Sex steroid hormone; Reproductive cycle; Ovarian follicle; Aquaculture; Oocyte maturation
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod63.6.1676

In vertebrates, the growth and maturation of the ovarian follicle is dependent on the appropriate dynamics of sex steroid secretion, which is dictated by gene expression of the steroidogenic enzymes. The molecular aspects of steroid regulation are poorly understood in fishes, so as a first step we determined the pattern of expression of four key steroidogenic genes throughout the ovarian cycle in an annually spawning teleost, the channel catfish ( Ictalurus punctatus ). The abundance of transcripts encoding 3β-hydroxysteroid dehydrogenase (3β-HSD) and cholesterol side chain cleavage (P450 scc ), 17α-hydroxylase/lyase (P450 c17 ), and aromatase (P450 arom ) were determined by rtqRT-PCR or ribonuclease protection assay and correlated to ovarian growth and plasma titers of estradiol (E 2 ) and testosterone (T) in two populations of catfish. Elevations in transcript abundance for P450 c17 , P450 scc , and P450 arom were observed at the onset of ovarian recrudescence and during early vitellogenic growth of the oocytes; however, all three decreased precipitously with the completion of vitellogenesis. Changes in the expression of these genes strongly suggest a direct correlation to E 2 and T titers. Alternatively 3β-HSD transcript abundance was relatively stable throughout the year. This study suggests that the genes encoding the three steroidogenic cytochrome P450s have a similar regulatory mechanism.