Isolation and characterization of carp prolactin

Area of Science:

• Comparative Endocrinology
• Fish Physiology
• Protein Biochemistry

Background:

• Prolactin (PRL) plays crucial roles in vertebrate physiology, including osmoregulation and reproduction.
• Characterizing fish PRL is essential for understanding its specific functions and evolutionary relationships.

Purpose of the Study:

• To isolate and purify prolactin from common carp (Cyprinus carpio) pituitary glands.
• To characterize the physicochemical and biological properties of carp prolactin.
• To develop a standardized procedure for fish prolactin isolation.

Main Methods:

• Acid-acetone extraction and purification using Sephadex G-75, DEAE-cellulose ion-exchange chromatography, and HPLC.
• Analysis of purity and molecular weight using HPLC and SDS-PAGE.
• Biological activity assessed by plasma Na+ retention in hypophysectomized killifish (Fundulus heteroclitus).
• Immunocytochemistry and immunoblotting to confirm antiserum specificity against carp PRL and growth hormone (GH).

Main Results:

• Successfully isolated carp prolactin with a yield of 0.7 mg/g wet tissue.
• Carp PRL exhibited biological activity comparable to ovine PRL in osmoregulation.
• Immunocytochemistry confirmed specific localization of PRL in goldfish rostral pars distalis without cross-reactivity to GH.
• Carp PRL identified with a molecular weight of 23 kDa and an isoelectric point of 7.3.

Conclusions:

• A robust purification protocol for carp prolactin was established.
• Carp PRL demonstrates conserved osmoregulatory functions across different fish species.
• The findings support a proposed standardized method for isolating fish PRLs, facilitating further research.