Demasculinisation of sexually mature male common carp, Cyprinus carpio, exposed to 4-tert-pentylphenol during spermatogenesis

Sexually mature male common carp (Cyprinus carpio) were exposed for a 3-month period to sublethal concentrations of 4-tert-pentylphenol (TPP) and to 17 beta-estradiol (E2) during spermatogenesis. This was part of a broad research programme investigating the effects of TPP on the life stages of the carp which might prove susceptible to endocrine disruption. Exposure of adult male carp to the pseudo-estrogen TPP, or to E2 during sexual maturation, led to elevated plasma levels of vitellogenin (P < 0.001), a typically female protein and to the inhibition of the spermatogenesis. The histological examination of the testes showed the progressive disappearance of spermatozoa and spermatogenic cysts, and a higher incidence of pathological alterations with time at all TPP and E2 concentrations (e.g. fibrosis, vacuolation and atrophy of the germinal epithelium). A reduced diameter of the seminiferous lobules (P < 0.001) was measured in fish testes exposed to all TPP concentrations for 3 months and in some TPP exposures, after 1 and 2 months. After a 3-month exposure, the spermatocrit values of fish exposed to the highest TPP concentration were significantly lower than those of the control (P < 0.01), whilst those fish exposed to the highest E2 concentration did not produce any milt. The occurrence of early ovo-testes in some fish with completely regressed testes suggests that oogenesis may proceed in testes which have first been inhibited (demasculinised) following estrogenic stimulus. (C) 1998 Elsevier Science B.V. All rights reserved.