FSH-, LH-, and TSH-expressing cells during development of Sparus aurata L. (Teleostei). An immunocytochemical study.

Follicle-stimulating hormone-like gonadotropin (FSH), luteinizing hormone-like gonadotropin (LH), and thyrotropin (TSH) cells were detected in adult and developing pituitary gland of gilthead seabream. Antisera obtained against the alpha- and beta-subunits of FSH (anti-My FSH) and the beta-subunit of LH (anti-My LHbeta), respectively, of the teleost Mediterranean yellowtail, and an antiserum against the beta-subunit of human TSH (anti-h TSHbeta), were applied to identify and follow these cells during ontogeny using light microscopy. FSH cells were immunoreactive to anti-My FSH serum, LH cells were immunoreactive to anti-My LHbeta and anti-My FSH sera, and TSH cells were immunoreactive to anti-h TSHbeta and anti-My FSH sera. In adult specimens, FSH and LH cells were located in both the proximal pars distalis (ppd) and the pars intermedia (pi) in strands or compact groups and as isolated cells. FSH cells were less numerous than LH cells. Some FSH and LH cells had a vacuolated appearance. TSH cells were mainly arranged as a mass in the anterior ppd, although some isolated cells could also be observed. FSH, LH, and TSH cells appeared at different times during development. FSH cells were observed for the first time in 22-day-old larvae and LH cells in juvenile specimens when the gonad was still undifferentiated. No vacuolated FSH and LH cells were present in larvae or juveniles. TSH cells were observed for the first time at hatching. As the fish developed, FSH, LH, and TSH cells progressively increased in number and showed the same distribution as in adult specimens.