Avian growth hormone receptor assay: use of chicken and turkey liver membranes.
A sensitive avian growth hormone (GH) radioreceptor assay (RRA) was developed using recombinant chicken growth hormone (rcGH) and a membrane receptor preparation of chicken or turkey livers. The specific binding of 125I-labeled rcGH to a 47,800 X g pellet was 33-36% in a 16-20 h incubation period at 4 degrees C. Binding was time, temperature and pH dependent. Scatchard analysis indicated a single class of high affinity GH binding sites in chicken and turkey livers, with binding affinities of 1.03 X 10(10) liter/M and 1.11 X 10(10) liter/M, respectively, and corresponding binding capacities of 10.7 fmol and 21 fmol per mg protein. The sensitivity of the assay was 0.41 ng of rcGH. Intra- and inter-assay coefficients of variation were 5.3% and 9.7%, respectively. Bovine GH, ovine GH, and porcine GH competed effectively for the GH binding sites in chicken and turkey livers. Turkey prolactin (PRL) and porcine PRL showed little cross-reaction (less than 0.07%), while cross-reaction of ovine and bovine PRL was greater (less than 10%). Standard rcGH (0.5-30 ng) was added to sera from hypophysectomized chickens and turkeys (hypox sera) and to tissue culture medium and was measured quantitatively. Untreated medium (10-100 microliters) and hypox sera (5-40 microliters) did not inhibit rcGH binding. These studies report the existence of specific binding sites for avian GH in chicken and turkey liver and validate a sensitive RRA for measurement of bioactive GH in sera and tissue culture medium.
Krishnan
K A
KA
U.S. Department of Agriculture, ARS, Avian Physiology Laboratory, Beltsville, MD 20705.
Proudman
J A
JA
Bahr
J M
JM
D000818:Animals; D002645:Chickens / Q000378:metabolism*; D003429:Cross Reactions; D013006:Growth Hormone / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000378:metabolism*; D015636:Magnesium Chloride / Q000494:pharmacology; D010907:Pituitary Hormones / Q000494:pharmacology; D011869:Radioligand Assay / Q000379:methods*; D011986:Receptors, Somatotropin / Q000378:metabolism; D013997:Time Factors; D014357:Trypsin / Q000502:physiology; D014422:Turkeys / Q000378:metabolism*; D010738:Type C Phospholipases / Q000502:physiology
D010907:Pituitary Hormones; D011986:Receptors, Somatotropin; D015636:Magnesium Chloride; D013006:Growth Hormone; D010738:Type C Phospholipases; D014357:Trypsin