Identification of the molecular forms of and steroid hormone response to gonadotropin-releasing hormone in the Australian lungfish, Neoceratodus forsteri

J. M P Joss, J. A. King*, R. P. Millar

*Corresponding author for this work

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Gonadotropin-releasing hormone (GnRH) peptides in the hypothalamus of the lungfish, Neoceratodus forsteri, were investigated by reverse-phase HPLC and RIA with region-specific antisera. Both chicken GnRH II and mammalian GnRH were identified, the latter being present in greater concentration. The steroidogenic response to a single intracardiac injection of synthetic mammalian GnRH was investigated in early and late spring (beginning and end of spawning season) and in early autumn. In early spring, both sexes responded with rapid and transient elevation of circulating steroid hormones. Testosterone in males showed the greatest response by elevating from 120 to 240 nmol/liter within 2 min of the injection and returning to ~100 nmol/liter within 15 min. Female lungfish showed a similar but slightly less dramatic response in circulating estradiol and testosterone. The responses of both males and females were reduced in late spring and abolished in early autumn, which is indicative of a period of seasonal refractoriness.

Original languageEnglish
Pages (from-to)392-400
Number of pages9
JournalGeneral and Comparative Endocrinology
Volume96
Issue number3
DOIs
Publication statusPublished - 1994

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