Sex steroids and the initiation of puberty in male African catfish (Clarias gariepinus).
The effects of sex steroids on spermatogenesis and testicular androgen secretion were studied in juvenile (spermatogonia present in testes) African catfish. Fish were implanted with Silastic pellets containing 11-ketotestosterone (KT), 11beta-hydroxyandrostenedione (OHA), androstenetrione (OA), androstenedione (A), testosterone (T), 5alpha-dihydrotestosterone (DHT), or estradiol-17beta (E2). Control groups received steroid-free pellets. Two weeks later, testis tissue fragments were incubated with African catfish luteinizing hormone (LH) and the amount of OHA secreted in vitro (the main androgen produced by African catfish testes) was quantified. Tissue fragments were then fixed for histological analysis of spermatogenesis. Treatment with KT, OHA, and OA stimulated testicular growth and spermatogenesis (spermatocytes and spermatids were found), whereas T, DHT, A, or E2 had no such effects. All steroids, except for DHT and E2, reduced OHA secretion in the absence and presence of LH to approximately 10% of the control values. Previous studies have shown that KT, OHA, and OA have little effect on circulating LH levels in juvenile male African catfish, so that these androgens probably had direct effects on the testis. Inasmuch as OHA, OA, and KT have largely similar effects and because OHA and OA are converted to KT in vivo, we suggest that KT is physiologically the most relevant androgen for the initiation of spermatogenesis in African catfish.
Cavaco
J E
JE
Utrecht University, Faculty of Biology, Department of Experimental Zoology, Research Group for Comparative Endocrinology, 3584 CH Utrecht, The Netherlands.
Vilrokx
C
C
Trudeau
V L
VL
Schulz
R W
RW
Goos
H J
HJ
D000735:Androstenedione / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D002397:Catfishes / Q000502:physiology*; D005837:Genitalia, Male / Q000033:anatomy & histology; D012739:Gonadal Steroid Hormones / Q000097:blood / Q000494:pharmacology*; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000494:pharmacology; D008297:Male; D009929:Organ Size / Q000502:physiology; D012727:Sex Characteristics; D013091:Spermatogenesis / Q000187:drug effects / Q000502:physiology; D013737:Testis / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
D012739:Gonadal Steroid Hormones; D000735:Androstenedione; C003582:11-hydroxyandrostenedione; D007986:Luteinizing Hormone