Objective
The main objective of the proposed research is to study the endocrinological control of growth in the sea bream (Sparus aurata) and the influence of non-hormonal factors on growth. This will involve:
Isolation and characterisation of growth hormone (GH) from sea bream pituitaries, and setting up of a GH radioimmunoassay;
Development of a radioreceptor assay for GH in order to determine the sites at which it acts and the response it evokes in tissue;
Determination of factors (biological and environmental) which regulate GH synthesis and release from the pituitary;
An investigation of how biological (e.g. hormones, sexual maturity) and environmental (e.g. social interactions, photoperiod, temperature etc.) factors act on body growth.
A study has been made of the endocrinological control of growth in the sea bream (Sparus aurata) and the influence of nonhormonal factors on growth.
Isolation and characterization of growth hormone (GH) from sea bream:
2 major protein bands of molecular weight 20kDa (GH) and 23kDa (prolactin) were identified in pituitary extracts. GH has been isolated from pituitary extracts and partially sequenced. The purified protein was used to raise a highly specific sea bream GH antisera. In bioassays the pure GH was bioactive and provoked a significantly greater increase in both weight and length than that in fish treated with bovine GH or controls. Also, a novel hormone like molecule, parathyroid hormone related protein was identified for the first time in fish.
A radioreceptor assay for GH:
A method for the isolation of microsomal membranes and a heterologous radioreceptor assay have been developed and the effect of different experimental protocols on the capacity of tissue to bind GH is being analysed. In control fish, liver was the tissue which contained the highest number of GH receptors.
Factors which regulate GH synthesis and secretion:
A system for the culture of sea bream pituitaries has been developed. The synthesis and secretion of GH is being determined in pituitaries incubated in culture medium containing different peptides and neurotransmitters.
Biological and environmental influences on growth:
Growth rate was found to be inversely related to stocking density and the range of sizes increase as the fish grow.
Stocking density does not have a significant effect on the size range of fish. Stocking with fish of a similar size did not affect the specific growth rate and the coefficient of variation did not change. With heterogenous stocking the coefficient of variation decreased from 32 to 22%.
The project will be carried out through the following phases :
Project planning, appointment of staff and acquisition of materials
Isolation, purification and chemical characterisation of sea bream GH
Development of heterologous and homologous radioreceptor assays for GH and other potential growth promoting hormones
Biological and environmental influences on growth throughout the life cycle of the sea bream.
Application of radioreceptor assay to tissue from sea bream of different age groups or which have been subjected to particular environmental conditions.
Production and characterisation of antisera against sea bream GH, GH receptors and potential growth promoting hormones.
RIA for growth hormone.
Regulation of GH secretion.
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8000 Faro Codex
Portugal