Growth hormone kinetics during adaptation to a hyperosmotic environment in rainbow trout

Sakamoto, Tatsuya; Ogasawara, Tsuyoshi; Hirano, Tetsuya

doi:10.1007/bf00258756

Cited by 58 publications

(40 citation statements)

References 43 publications

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“…It has been speculated that this is due to an increased metabolic clearance rate of GH as a result of increased GH receptor expression in peripheral tissues, representing a third stage in the activation of the GH system. Although no data exist on GH receptor densities or GH clearance rate during smoltification, the process is a pre-adaptation to life in SW, and SW transfer of rainbow trout has been shown to increase GH clearance rate (Sakamoto et al 1990).…”

Section: Discussionmentioning

confidence: 99%

“…In salmonids, plasma GH levels usually increase transiently following seawater (SW) entry (see Björnsson 1997). In coho salmon (Oncorhynchus kisutch) and rainbow trout (O. mykiss), both the clearance rate and the calculated secretion rate of GH increased after transfer to SW (Sakamoto et al 1990. Also, in amago salmon (O. masou), the response of GH mRNA to SW exposure appears to be related to the development of preparatory mechanisms for SW entry, indicating that GH mRNA increases before SW entry (Yada et al 1992).…”

Section: Introductionmentioning

confidence: 99%

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Growth hormone endocrinology of Atlantic salmon (Salmo salar): pituitary gene expression, hormone storage, secretion and plasma levels during parr-smolt transformation

Ágústsson¹,

Sundell²,

Sakamoto³

et al. 2001

Journal of Endocrinology

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A number of studies on the Atlantic salmon (Salmo salar), have reported changes in plasma GH during parr-smolt transformation, but there is a lack of information about the endocrinology of the GH system during this process. In order to elucidate the mechanisms underlying these changes in plasma GH levels during the parr-smolt transformation of Atlantic salmon, GH mRNA expression in the pituitary was studied together with total pituitary GH content, in vitro GH secretion rate and plasma GH and IGF-I levels. Atlantic salmon were kept in outside tanks, under natural condition from early February until late June. Approximately three times a month fish were killed and pituitaries and blood were sampled for investigation. Further, pituitaries were moved to the laboratory for in vitro GH secretion studies. The results show that the GH system is first activated by an increase in GH secretion rate, which leads to an increase in plasma GH levels and causes a drop in the total GH content of the pituitary. This drop in pituitary GH content is later reversed by an increased GH synthesis seen as an increase in GH mRNA expression. Maximal activation of the GH system is seen to occur in early May, when plasma IGF-I levels reach highest levels, after which a certain deactivation of the GH system takes place. The data show that plasma levels of GH are to a large extent regulated by the secretion rate from the pituitary, although changes in the GH clearance rate are also likely to take place and influence the plasma GH levels. The study further underlines the significant role that the GH-IGF-I axis plays in the parr-smolt transformation of the Atlantic salmon.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Growth hormone endocrinology of Atlantic salmon (Salmo salar): pituitary gene expression, hormone storage, secretion and plasma levels during parr-smolt transformation

Ágústsson¹,

Sundell²,

Sakamoto³

et al. 2001

Journal of Endocrinology

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“…Circulating GH is significantly increased 24-48 h following seawater transfer and then decreases, reaching levels found in freshwater thereafter (Sakamoto et al, 1990(Sakamoto et al, , 1991. Furthermore, 4 days after seawater transfer, both GH metabolic clearance and secretion rate have been shown to be five times higher than those found in freshwater adapted trout (Sakamoto et al, 1990). No information is available on GH receptor turnover in fish.…”

Section: Figmentioning

confidence: 97%

Identification and Modulation of a Growth Hormone-Binding Protein in Rainbow Trout (Oncorhynchus mykiss) Plasma during Seawater Adaptation

Sohm

Manfroid

Pezet

et al. 1998

General and Comparative Endocrinology

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A soluble protein that specifically bound 125 I-human growth hormone (hGH) was identified in rainbow trout plasma, using HPLC-gel filtration. The binding affinity of the protein for hGH was 1.2 ؋ 10 9 M ؊1 . 125 I-rainbow trout GH (tGH) was also able to bind to the protein albeit with a lower affinity (6.6 ؋ 10 7 M ؊1 ) than hGH. Crosslinking experiments using 125 I-hGH revealed two specific bands of 150 and 130 kDa. The complex 125 I-hGH-BP could be precipitated by a monoclonal anti-GH receptor antibody, suggesting a close relationship between the plasma GH-BP and the GH receptor. A fourfold increase in the hGH binding to the GH-BP was shown 48 h after transfer of the fishes from freshwater to seawater. The increase in binding was related to a high binding capacity without significant changes in binding affinity. These results suggest a potential role of this related GH-BP as an index of GH effects during seawater adaptation in salmonids.1998 Academic Press

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“…All hormone doses were chosen to be within the range commonly used in studies of osmoregulatory endocrinology in fish. Based on studies of hormone dynamics and clearance values in a variety of fish species (Hirano & Utida 1971, Weisbart et al 1987, Sakamoto et al 1990, Duan & Hirano 1991, Mancera et al 1994, Shrimpton & Randall 1994, the chosen doses were expected to give temporarily supra-physiological serum levels and metabolic half-lives in the range of 3-12 h.…”

Section: Experimental Protocolsmentioning

confidence: 99%

Distinct hormonal regulation of Na+,K+-atpase genes in the gill of Atlantic salmon (Salmo salar L.)

Tipsmark

Madsen²

2009

Journal of Endocrinology

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It has recently become evident that maintenance of ionic homoeostasis in euryhaline salmonids involves a reciprocal shift in expression of two isoforms of the gill Na+,K+-atpase α-subunit when the surrounding salinity changes. The present study investigated the regulation of this shift between the α1a (freshwater (FW) isoform) and the α1b (seawater (SW) isoform) by cortisol, Gh, prolactin (Prl) and Igf 1. Injection with cortisol into FW salmon increased α1a expression, while Gh had no effect. Conversely, both cortisol and Gh stimulated α1b expression, and a significant synergy was observed. igf1 expression was increased by Gh in both gill and liver, and inhibited by cortisol in the liver. Gill igf1 and gh receptor expression increased in response to cortisol. Injection with Prl into SW salmon compromised their hypo-osmoregulatory performance, selectively reduced the expression of the α1b isoform and decreased enzymatic Na+,K+-atpase activity in the gill. Cortisol and Prl reduced gill and liver igf1 expression, and both hormones stimulated gill igf1 receptor expression. In a short-term experiment with incubation of FW gill cell suspensions, cortisol stimulated α1a and α1b expression, while Igf1 stimulated only α1b. The data elaborate our understanding of Prl and Gh as being antagonists in the control of gill ion regulation, and support a dual role for Gh involving endocrine and paracrine Igf1 action. Gh and Prl may be the decisive stimuli that direct cortisol-aided mitochondrion-rich cell development into either secretory or absorptive types.

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Growth hormone kinetics during adaptation to a hyperosmotic environment in rainbow trout

Cited by 58 publications

References 43 publications

Growth hormone endocrinology of Atlantic salmon (Salmo salar): pituitary gene expression, hormone storage, secretion and plasma levels during parr-smolt transformation

Growth hormone endocrinology of Atlantic salmon (Salmo salar): pituitary gene expression, hormone storage, secretion and plasma levels during parr-smolt transformation

Identification and Modulation of a Growth Hormone-Binding Protein in Rainbow Trout (Oncorhynchus mykiss) Plasma during Seawater Adaptation

Distinct hormonal regulation of Na+,K+-atpase genes in the gill of Atlantic salmon (Salmo salar L.)

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