Androgens induce renal synthesis of urinary lipocalin-family protein, a potential inter-sexual transmitter in viviparous rockfish

Abstract

In viviparous black rockfish (Sebastes schlegelii), the kidney of reproductive-phase males actively produces lipocalin-type prostaglandin D₂ synthase homolog (LPGDSh) protein, which is presumably involved in inter-sexual communication when emitted in the urine. The present study was undertaken to discover whether androgens and their nuclear receptors (Ars) are engaged in regulation of renal LPGDSh protein synthesis in black rockfish. Quantitative real-time polymerase chain reaction, in conjunction with immunohistochemistry and highly sensitive enzyme-linked immunosorbent assay, revealed that intra-abdominal administration of a synthetic androgen, 17α-methyltestosterone (MT), to juvenile black rockfish induced their renal expression of LPGDSh transcript and protein. In situ hybridization visualized arα and arβ transcripts in the renal tubules of mature males during the copulation season, where they were co-localized with LPGDSh protein. Androgens, such as 11β-hydroxytestosterone, MT, dihydrotestosterone, 11-ketotestosterone (11KT), testosterone, and androstenedione transactivated a luciferase reporter vector containing four repeats of a consensus androgen response element (ARE) in the presence of black rockfish Ars (either Arα or Arβ), with differences in ligand-preference and dose-response profiles being observed between the two Ars. In the presence of 11KT, the Ars transactivated a reporter vector containing the proximal 5′-flanking region of an LPGDSh gene in luciferase reporter assays. The region between 2100 bp and 1110 bp upstream from the start codon of the LPGDSh gene, wherein many ARE-like motifs are densely distributed, was imperative for the androgenic transactivation response of the 5′-flanking region. Collectively, these observations verify that renal synthesis of LPGDSh protein is upregulated by androgens.