Human Growth Hormone (hGH) is a monomeric 22 kilo Dalton (kDa), 191 amino acid protein with an isoelectric point (pI) close to pH 5, produced in the anterior pituitary gland. High level production of somatropin (recombinant hGH) is done in Escherichia coli (E. coli) to meet the demand and to avoid possible Creutzfeldt-Jacob disease (CJD).

We have grown polarized epithelial Madin-Darby canine kidney II (MDCK II) cells on filters in the presence of [35S]sulfate, [3H]glucosamine, or [35S]cysteine/[35S]methionine to study proteoglycan (PG) synthesis, sorting, and secretion to the apical and basolateral media. Whereas most of the [35S]sulfate label was recovered in basolateral PGs, the [3H]glucosamine label was predominantly incorporated into the glycosaminoglycan chains of apical PGs, indicating that basolateral PGs are more intensely sulfated than their apical counterparts. Expression of the PG serglycin with a green fluorescent protein tag (SG-GFP) in MDCK II cells produced a protein core secreted 85% apically, which was largely modified by chondroitin sulfate chains. Surprisingly, the 15% of secreted SG-GFP molecules recovered basolaterally were more heavily sulfated and displayed a different sulfation pattern than the apical counterpart. More detailed studies of the differential modification of apically and basolaterally secreted SG-GFP indicate that the protein cores have been designated to apical and basolateral transport platforms before pathway-specific, post-translational modifications have been completed.

The molecular structures of the receptors of growth hormone and prolactin have recently been identified by molecular cloning, and have been characterized in a number of species and different tissues. The receptors consist of one polypeptide chain with a single transmembrane region. The extracellular region contains cysteines for disulphide bonding and potential sites for glycosylations. The intracellular part which mediates the biological actions displays considerable heterogeneity of size. A high degree of homology is demonstrated between the extracellular part of these receptors and the receptors of a number of cytokines, interferons and growth factors. Together they comprise a new family of receptors called the cytokine/growth hormone/prolactinreceptor family. Their structure is reviewed, along with the actions of growth hormone and prolactin in vivo. In spite of numerous biological effects the molecular mechanisms of actions for this class of receptors are unknown, even though they convey important cell regulatory functions. The molecular analysis of growth hormone receptor has provided new medical insight on the results of growth hormone replacement therapy in persons with deficient growth.

Serum prolactin (PRL), total estrogen and androgen levels were measured monthly from May to September in adult Atlantic salmon. The fish were kept in sea water with no significant osmotic changes throughout the sampling period. Serum PRL in sexually maturing males and females, which spawned in November, and three immature females reached maximum levels (mean 10.6 ng/ml) at the end of June and declined thereafter. A significant increase in total androgen and estrogen levels in the maturing fish was not found until August-September. The results did not indicate any primary role for PRL in the regulation of sexual maturation in Atlantic salmon. However, a permissive action of PRL should not be excluded. The possible participation of PRL in the preadaptation for fresh water migration is discussed.

Highly purified growth hormone (GH) has been isolated from Atlantic salmon (Salmo salar) pituitaries by extraction with acid acetone, acidic precipitation, and reversed-phase high-performance liquid chromatography (HPLC). The yield was 2.5 mg/g wet tissue. The Atlantic salmon GH (sGH) emerged as a single symmetrical peak after HPLC on a reverse phase C18 column. SDS-gel electrophoresis revealed only one band with an estimated molecular weight of 23,000. Atlantic sGH showed a uniform molecular weight, but two-dimensional (2D) gel electrophoresis of the purified sGH revealed charge heterogeneity with pI's ranging from 6.5 to 8.2. Treatment of the purified sGH with alkaline phosphatase concentrated these different forms into a single more alkaline position (pI 8.2) indicating removal of acidic groups. These results were documented using both silver- and immunostaining of the 2D SDS gels. The purified sGH was phosphorylated in vitro by a calmodulin-dependent protein kinase. Phosphorylation of sGH may be a post-translational modification resulting in several molecular forms with variable acidity. Analysis of the amino acid composition of Atlantic sGH revealed homology with GHs isolated from other teleost species and the amino-terminal sequence showed only three different amino acids within the first 25 residues compared to GH isolated from chum salmon (Oncorhynchus keta) and coho salmon (Oncorhynchus kisutch) pituitaries. Atlantic sGH had a methionine as the amino-terminal residue. Antibodies against chum sGH cross-reacted with Atlantic sGH. Antibodies against either Atlantic or chinook (Oncorhynchus tschawytscha) salmon prolactin or human GH did not cross-react with Atlantic sGH. Atlantic sGH was shown to have a slight growth-promoting activity in the rat tibia assay.

Prolactin was isolated from the Atlantic salmon (Salmo salar) pituitary gland by extraction with acid acetone, gel filtration, ion exchange-chromatography, and reversed-phase high-performance liquid chromatography. The yield was 0.6 mg/g wet tissue. The hormone had a molecular weight of 23.5 kDa as determined by SDS-polyacrylamide gel electrophoresis. Isoelectric focusing gave an isoelectric point of 9.2. The N-terminal sequence and the amino acid composition indicated extensive homology between Atlantic and Pacific salmon prolactin. Antiserum against Atlantic salmon prolactin cross-reacted with chum salmon prolactin, but not with human, rat, or sheep prolactin.