Parvalbumin 5 potentially regulates Fsh cells but not Lh cells in the pituitary of ricefield eels

Parvalbumins (Pvalb) are members of the EF-hand protein superfamily which have been shown to play important roles in the nervous system and muscle. In the present study, the expression and potential roles of parvalbumin 5 (Pvalb5), a member of Parvalbumin subfamily, was characterized in a teleost the ricefield eel. RT-PCR analysis revealed a very restricted tissue distribution of pvalb5 mRNA, with dominant expression in the pituitary and eye of both female and male ricefield eels. Specific antisera against ricefield eel Pvalb5 were generated, and immunohistochemical analysis showed the presence of Pvalb5 in the adenohypophysis of adult fish but not of juveniles (about 4-month-old). Dual immunofluorescent immunostaining indicated the expression of Pvalb5 in Fsh cells but not in other pituitary tropic hormone-producing cells including Lh, Tsh, Gh, or Prl. Overexpression of pvalb5 increased Fsh release but not Lh release in primary pituitary cells. Results of the present study suggest that Pvalb5 may be specifically involved in the regulation of Fsh release in the pituitary of ricefield eels, which advances our understanding of the mechanisms underlying the differential regulation of Fsh and Lh release in vertebrates.