title: An assay for plasma somatomedin: [3H]thymidine incorporation by isolated rabbit chondrocytes.
abstract: The incorporation of [3H]thymidine by rabbit chondrocytes in vitro has been developed as a sensitive assay for plasma somatomedin. A concentration of normal plasma of 2-5% enhanced [3H]thymidine incorporation by 5- to 20-fold compared with basal levels in the absence of plasma. The mean potency of plasma from normal adult men was 0-96+/-0-1 u./ml (mean+/-S.D.) and from acromegalic patients 1-9+/-0-4 u./ml. The apparent potency of hypopituitary plasma alone increased on heating which suggested the presence of heat-labile inhibitors of somatomedin activity. The potency of heated hypopituitary plasma (0-6+/-0-09 u./ml) remained significantly lower (P less than 0-01) than normal plasma. Human growth hormone (0-1-20 muu./ml), bovine growth hormone (0-5 20 muu./ml), insulin (0-5-5 muu./ml) and glucose (0-3-2 mmol/1) had no direct effect on the incorporation of [3H]thymidine. Chondrocytes which had been previously stored frozen also showed a response to plasma somatomedin.
mesh_terms: D000172:Acromegaly / Q000097:blood; D000818:Animals; D001681:Biological Assay; D002356:Cartilage / Q000166:cytology / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D013006:Growth Hormone / Q000494:pharmacology; D006358:Hot Temperature; D006801:Humans; D007018:Hypopituitarism / Q000097:blood; D007328:Insulin / Q000494:pharmacology; D011817:Rabbits; D013002:Somatomedins / Q000097:blood*; D013936:Thymidine / Q000378:metabolism
chemical_list: D007328:Insulin; D013002:Somatomedins; D013006:Growth Hormone; D005947:Glucose; D013936:Thymidine