T6 AM Environmental Hypoxia
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 324-326

(THO-1117-822334) Neuroendocrine changes associated with reproductive dysfunction in Atlantic croaker after exposure to hypoxia.

Thomas, P¹, Rahman, S¹, Kummer, J¹, Khan, I¹, ¹ University of Texas Marine Science Institute, Port Aransas, Texas, USA

ABSTRACT- Previously we have shown that chronic laboratory and field exposure to low moderate hypoxia causes a dramatic impairment of reproductive processes and endocrine function in Atlantic croaker (Micropogonias undulatus). In females, decreases in plasma estradiol, hepatic estrogen receptor mRNA, and plasma vitellogenin levels were observed, indicating an impairment of estrogen signaling after hypoxia exposure. Several indices of neuroendocrine function were also measured to determine whether these endocrine disturbances are due to hypoxia-induced changes at higher levels of the hypothalamus-pituitary-gonad axis. Gonadotropin secretion in response to a gonadotropin releasing hormone (GnRH) injection was attenuated after hypoxia exposure. Hypothalamic GnRH mRNA levels were also decreased, indicating a disturbance of neuroendocrine function in hypoxia-exposed fish. The results suggest the neuroendocrine system is a major site of interference by low dissolved oxygen resulting in reproductive dysfunction in fishes.

Key words: neuroendocrine effects, reproductive dysfunction, hypoxia, Atlantic croaker