title: The nature of pituitary large growth hormone as studied by immunoabsorption.
abstract: Porcine pituitaries were homogenized in neutral pH buffer and the supernatant layer after centrifugation was fractionated by gel filtration on Sephadex G-200. The void volume peak contained 0.2-0.5% of the immunoreactive growth hormone (large GH), the remainder (small GH) eluted at Kd 0.6. The isolation of large GH was attempted with anti-GH coupled to Sepharose 2B: of the immunoreactive large GH 50-60% was absorbed to a large excess of anti-GH Sepharose during an 18 h incubation at 4 degrees C. Over 80% of the absorbed immunoreactivity could be eluted with neutral 6M-sodium thiocyanate at 4 degrees C. The eluate, when rechromatographed, contained small GH, RNA which had absorbed to anti-GH Sepharose remained in the void volume on rechromatography. RNA was also absorbed when Sepharose-coupled bovine serum gamma-globulin was substituted for anti-GH Sepharose or when rat liver was substituted for porcine pituitaries. No RNA was absorbed when large GH was converted into small GH with 6M-NaSCN and rechromatographed before immunoabsorption. However, significant absorption of prolactin was found. After a two-hour incubation of porcine pituitary slices with [3H]leucine, GH dissociated from large GH had a specific activity 10-100 times that of small GH but appeared similar to it by gel chromatography and polyacrylamide gel electrophoresis. We conclude that pituitary large GH represents a different metabolic pool from pituitary small GH and may be newly synthesized small GH not yet incorporated into granules, thus being susceptible to non-specific binding to RNA during the extraction procedure.
mesh_terms: D000818:Animals; D000937:Antigen-Antibody Reactions; D003429:Cross Reactions; D013006:Growth Hormone / Q000096:biosynthesis* / Q000276:immunology; D008970:Molecular Weight; D010902:Pituitary Gland / Q000378:metabolism*; D013552:Swine; D013861:Thiocyanates
chemical_list: D013861:Thiocyanates; D013006:Growth Hormone