Pituitary factor

Attempts have been made to purify the pituitary factor that stimulates thyroid secretion (thyrotropin). A single homogeneous product has not yet been obtained. When the active TSH is purified from beef, sheep, or whale hypophyseal extracts by countercurrent extraction and acetone fractionation, followed by chromatographic analysis on diethylaminoethyl-cellu-lose, several active components are always detected by starch-gel electrophoresis of the chromatography eluents. 

Hormoproteins.—Several of the internal secretions of the human body have been found to be proteins or protein derivatives. Chief among these protein hormones are insulin, secretin, thyro-globulin, prolactin and other pituitary factors, parathyrin. The simple autaooids, adrenaline and thyroxine are amino acid derivatives. 

The hypoglycsemia due to phloridzin injections or starvation can be alleviated in hjq)ophysectomised dogs by feeding with carbohydrate or protein, but not by feeding with fat, which has led Soskin (1935) to conclude that the pituitary factor promotes the conversion of fatty acids into sugar. 

The possible conversion of fat to carbohydrate within the organism has been a subject of much controversy. While the glycerol component of the fat molecule can be transformed readily into liver glycogen, a carbohydrate precursor has not yet been identified among the products of fatty acid metabolism. The existence of a pituitary factor in carbohydrate metabolism has been established, and one of its effects is ascribed to promotion of glycogenesis from fatty acids. 

Pituitary Factors in Ovarian Activity.—The anterior lobe of the pituitary gland secretes two factors, which on account of their action on the sex glands are called gonadotropic hormones. 

It was known as early as the 1920s that the pituitary gland contained a factor that could promote growth, but not until 1956 (1) was the factor isolated. hGH is extremely abundant in the pituitary, representing as much as 10% of this gland s dry weight, or 8 mg of hormone per gland (2). 

J (339), a 28-amino acid peptide, is a member of a family of stmctuially related peptides that includes secretin [1393-25-5] (340), growth hormone releasing factor (GRF), and pituitary adenylate cyclase-activating peptide (PACAP) [137061(341) (83). 

Inhibin and Activin. Inhibin, a water-soluble, gonadal factor known for over 50 years to inhibit pituitary function, has been isolated and identified (127—130). Inhibin is a glycoprotein hormone that preferentially inhibits the secretion of FSH. It consists of an a-chain subunit, mol wt 14,000, linked by disulfide bonds to a P-chain subunit, mol wt 18,000. There exist two forms of the P-chain subunit, P-A and P-B. The smaller subunit combines with either the P-A or P-B subunit to form inhibin-A or inhibin-B, respectively. 

Pituitary Growth Factor (from human pituitary giand) [336096-71-0]. Purified by heparin and copper affinity chromatography, followed by chromatography on carboxymethyl cellulose (Whatman 52). [Rowe et al. Biochemistry 25 6421 1986.]... 

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