Abstract
Summary
A highly sensitive, specific and reproducible double antibody RIA for measuring oxytocin in unextracted serum of cattle was developed. Serum concentrations of oxytocin were significantly (P < 0.05) elevated from 8.0 ± .11 μU/ml to 25 ± 7.6 μU/ml (mean ± SE) 2 min after commencement of milking. The range of peak oxytocin concentrations seen 2 min after milking in six animals was 11.2-65 μU/ml. The T1/2 for oxytocin, after milk ejection, was 3.6 min. Simultaneous determinations of oxytocin activity in blood sera and intramammary pressure were monitored in two cows before, during and after stimulation of the milk ejection reflex. Oxytocin activity in blood closely paralled changes in intramammary pressure.
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