An homologous radioimmunoassay for chicken follicle-stimulating hormone: observations on the ovulatory cycle.

A highly purified FSH preparation has been used to develop a specific homologous radioimmunoassay for chicken FSH which is sufficiently sensitive and precise to measure the hormone in small sample (10-100 microliter) of plasma. The assay was used to measure plasma FSH in the chicken and turkey. The FSH concentration was higher in sexually mature chickens than in juvenile birds and further elevated after castration or ovariectomy. In turkeys, it was lower in birds held on a short daily photoperiod than in birds held on a long daily photoperiod. FSH rose in sexually quiescent female turkeys after injection of synthetic LH-releasing hormone and was increased in laying hens after injection of progesterone. No major changes were observed in FSH concentration during the chicken ovulatory cycle, although there was a small increase 15 and 14 h before ovulation.