title: Radioimmunoassay of canine growth hormone.
abstract: A sensitive radioimmunoassay (RIA) for canine growth hormone (GH) was developed. Antibodies were elicited in rhesus monkeys. One antiserum exhibited a working titer at a dilution of 1: 500 000. Radioiodination was performed enzymatically employing lactoperoxidase. Logit-log transformation and least squares fitting resulted in straight line fitting of the standard curve between 0.39 and 50 ng/ml. Formation of large-molecular [125I]GH during storage caused diminished assay sensitivity. Therefore [125I]GH was re-purified by gel chromatography. Using this procedure, high and reproducible assay sensitivity was obtained. Tracer preparations were used for as long as 3 months after iodination. Diluted plasma from normal and acromegalic dogs resulted in a dose-response curve parallel to the standard curve. Canine prolactin exhibited a cross-reactivity of 2%. The within-assay coefficient of variation (CV) was 3.8 and the between-assay CV was 7.2%. Mean plasma GH concentration in normal dogs was 1.92 +/- 0.14 ng/ml (mean +/- SEM). GH levels in acromegalic dogs were appreciably higher. Insulin-induced hypoglycaemia, arginine and ornithine administration resulted in inconsistent and sluggish GH increment. A better response was obtained by injecting a low dose of clonidine. Clonidine administration to hypopituitary dogs resulted in absent or poor GH increment.
mesh_terms: D000172:Acromegaly / Q000097:blood / Q000662:veterinary; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002850:Chromatography, Gel; D003000:Clonidine / Q000494:pharmacology; D004285:Dogs / Q000097:blood*; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007018:Hypopituitarism / Q000097:blood / Q000662:veterinary; D007114:Immunization; D009952:Ornithine / Q000494:pharmacology; D011863:Radioimmunoassay / Q000379:methods*
chemical_list: D013006:Growth Hormone; D001120:Arginine; D009952:Ornithine; D003000:Clonidine