Bioassay for salmon prolactin using hypophysectomized Fundulus heteroclitus.

Area of Science:

• Endocrinology
• Comparative Physiology
• Aquaculture Research

Background:

• Salmon prolactin (PRL) plays a crucial role in osmoregulation.
• Existing bioassays for PRL lack sufficient speed, sensitivity, or specificity.
• Accurate measurement of PRL is essential for understanding fish physiology and aquaculture.

Purpose of the Study:

• To develop and validate a novel, rapid, sensitive, and specific bioassay for salmon prolactin (PRL).
• To characterize the biological activity of purified chinook and coho salmon PRL using the developed assay.

Main Methods:

• A bioassay was established based on the sodium-retaining action of PRL in hypophysectomized killifish (Fundulus heteroclitus).
• Purified PRL from chinook salmon (Oncorhynchus tschawytscha) and coho salmon (O. kisutch) were isolated using acid buffer polyacrylamide disc gel electrophoresis.
• The isolated salmon PRLs were characterized by molecular weight (MW ca. 22,000) and isoelectric point (pI > 9).

Main Results:

• The developed salmon PRL bioassay demonstrated high sensitivity (250 pg PRL per gram of fish), speed, and specificity.
• The assay successfully characterized the biological activity of purified chinook and coho salmon PRL.
• The isolated salmon PRLs exhibited properties consistent with known PRL characteristics.

Conclusions:

• A robust and efficient bioassay for salmon prolactin has been successfully developed.
• This assay provides a valuable tool for future research in salmonid endocrinology and osmoregulation.
• The characterized salmon PRLs confirm their biological activity and pave the way for further functional studies.