Abstract
A homologous double-antibody radioimmunoassay (RIA) for bovine thyrotropin (bTSH) has been developed. Antibody to bTSH was prepared by injecting with bTSH (NIH-TSH-B7) emulsified in Freund's complete adjuvant to guinea pigs. Antibody to guinea pig gamma globulin (GPGG) was prepared by immunizing rabbits with GPGG emulsified in Freund's complete adjuvant. In the RIA for bTSH, bovine prolactin did not show any significant cross-reaction. Bovine growth hormone, luteinizing hormone and follicle-stimulating hormone showed only a slight non-parallel inhibition. The inhibition curves of bovine plasma and pituitary TSH were parallel to that of bTSH standard (NIH-TSH-B7). The average recovery of bTSH added to bovine plasma was 104.6%. The sensitivity of the assay was 5ng/ml for the bTSH standard. The coefficients of variation within and between assays were 4.9% and 11.2%, respectively. Intravenous injection of synthetic thyrotropin releasing hormone (TRH) caused an elevation of plasma TSH concentration in lactating cows within 5min, and the peak level was observed after 15 to 20min. The elevation of plasma TSH after TRH administration in the lactating cow was completely inhibited by a short-term pretreatment with thyroid hormones.
