A radioimmunoassay for bovine parathyroid hormone.

A radioimmunoassay for bovine parathyroid hormone (bPTH) has been developed. An antibody was raised in a goat against 1-84 b PTH which was directed against the carboxy-terminal part of the molecule (no cross-reactivity with synthetic 1-34 b PTH fragment). 1-84 b PTH was labelled with 125I using the chloramine-T method. The tubes were incubated at 4 degrees C for 6 days in an equilibrium system with 25% protein concentration. Separation was performed using plasma-coated charcoal. Jugular venous plasma PTH levels were shown to be increased in hypocalcemic parturient cows.