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Journal of Comparative Physiology B

, Volume 162, Issue 7, pp 575–580 | Cite as

Inhibition of growth hormone synthesis by somatostatin in cultured pituitary of rainbow trout

  • Takashi Yada
  • Tetsuya Hirano
Article

Summary

When the pituitary of rainbow trout (Oncorhynchus mykiss) was incubated in a serum-free medium, a high level of growth hormone release as well as an activation of growth hormone synthesis were observed, suggesting the existence of hypothalamic inhibitory factor(s) on growth hormone synthesis. Although an inhibitory effect of somatostatin on growth hormone release is well established in both mammals and teleosts, an effect on growth hormone synthesis has not been demonstrated. In this study, we examined the effect of somatostatin on growth hormone synthesis in organ-cultured trout pituitary using immunoprecipitation and Northern blot analysis. Somatostatin inhibited growth hormone release from the cultured pituitary within 10 min after addition without affecting prolactin release. Incubation of the pituitary with somatostatin also caused a significant reduction in newly-synthesized growth hormone in a dose-related manner, as assessed by incorporation of [3H]leucine into immunoprecipitable growth hormone. There were no changes in the level or molecular length of growth hormone mRNA after somatostatin treatment, as assessed by Northern slot blot and Northern gel blot analyses. Human growth hormone-releasing factor stimulated growth hormone release, although the spontaneous synthesis of growth hormone was not augmented. However, somatostatin-inhibited growth hormone synthesis was restored by growth hormone-releasing factor to the control level. The spontaneous increase in growth hormone synthesis observed in the organ-cultured trout pituitary may be caused, at least in part, by the removal of the inhibitory effect of hypothalamic somatostatin.

Key words

Growth hormone Somatostatin Pituitary Synthesis Rainbow trout, Oncorhynchus mykiss 

Abbreviations

GH

growth hormone

GHRF

GH-releasing factor

PRL

prolactin

SDS

sodium dodecyl sulphate

SRIF

somatostatin (somatropin release-inhibiting factor)

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Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Takashi Yada
    • 1
  • Tetsuya Hirano
    • 1
  1. 1.Ocean Research InstituteUniversity of TokyoTokyoJapan

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