Effects of exogenous thyroxine (T4) and triiodothyronine (T3) on spontaneous metamorphosis and serum T4 and T3 levels in immediately premetamorphic sea lampreys,Petromyzon marinus

Lampreys: Biology, Conservation and Control

“…Spontaneous metamorphosis is a synchronous developmental process of extensive morphological, physiological, and behavioral changes (Youson 1988;Youson 2003) beginning in the summer months and characterized by a sharp decline in serum thyroid hormone (TH) levels in the early stages of metamorphic development (e.g., Wright and Youson 1977;Lintlop and Youson 1983b;Leatherland et al 1990;Youson et al 1994;see Sect. Precocious metamorphosis has been induced in some lamprey species, out of season, following goitrogen treatments (Hoheisel and Sterba 1963;Suzuki 1986Suzuki , 1989Holmes and Youson 1993;) which depress serum TH levels (Suzuki 1986(Suzuki , 1989Youson et al 1995b;Manzon and Youson 1997;Manzon et al 1998) as in the early stages of spontaneous metamorphosis. Precocious metamorphosis has been induced in some lamprey species, out of season, following goitrogen treatments (Hoheisel and Sterba 1963;Suzuki 1986Suzuki , 1989Holmes and Youson 1993;) which depress serum TH levels (Suzuki 1986(Suzuki , 1989Youson et al 1995b;Manzon and Youson 1997;Manzon et al 1998) as in the early stages of spontaneous metamorphosis.…”

“…By maintaining elevated TH concentrations with exogenous T 4 or T 3 , KClO 4 -induced metamorphosis is completely blocked (Manzon and Youson 1997;Manzon et al 1998;Fig. By maintaining elevated TH concentrations with exogenous T 4 or T 3 , KClO 4 -induced metamorphosis is completely blocked (Manzon and Youson 1997;Manzon et al 1998;Fig.…”

“…Included among these are the Manzon et al 1997) hypothalamic-pituitary (HP) axis which regulates the synthesis and secretion of T 4 , and to a lesser extent T 3 , from thyroid tissue, serum TH distributor proteins (THDP) which transport TH through the blood and regulate hormone availability, cytosolic deiodinases which regulate TH action via the conversion of T 4 to the more biologically active T 3 and the inactivation of both T 4 and T 3 , and finally the TH nuclear receptors (TRs) and their heterodimeric partners, the retinoid-X-receptors (RXRs), which act as ligand-regulated transcription factors to modulate gene expression. The vertebrate thyroid system consists of numerous regulatory points which act collectively to regulate TH action.…”

“…Moreover, these data are difficult to interpret because of the asynchronous development associated with induced metamorphosis Manzon and Youson 1997;Manzon et al 1998Manzon et al , 2001; see Sect. To clarify a role in metamorphosis and regulation of the thyroid axis, examined GnRH levels during KClO 4 -induced metamorphosis.…”

Study of the relationship between thyroid hormones and lipid metabolism during KClO4-induced metamorphosis of landlocked lamprey, Petromyzon marinus

“…For example, numerous studies have reported high levels of TH in premetamorphic larvae and that these levels decline sharply at the time external changes are first evident in spontaneous metamorphosis of lampreys [15][16][17]27,29,30,34]. In addition, spontaneous metamorphosis in sea lampreys was inhibited by T3 treatment [40]. Moreover, potassium perchlorate (KClO 4 ) induced the metamorphosis of three Northern Hemisphere lamprey species, Lampetra planer [9], Lampetra reissneri [28], and Petromyzon marinus; in P. marinus, KClO 4 -induced metamorphosis was accompanied by reduced T4 and T3 concentrations [10,18,39].…”