Radioactive Phosphorus Uptake by Chick Testes as an End-point for Gonadotropin Assay1

Abstract

The uptake of P³² by chick testes, expressed as counts/min/mg, provides a sensitive assay for ovine luteinizing hormone (N.I.H.-LH-S-l). A 4-point balanced assay demonstrated that significant responses can be produced by 1.0 μg and 1.5 μg of N.I.H.-LH. It also was observed that the N.I.H. hormone retained its potency after storage for 1 year. A dosage of approximately 10 times as much N.I.H.-FSH by weight was required to produce responses equivalent to those which accompanied LH administration. It is apparent, therefore, that LH can markedly stimulate chick testes. There was no synergistic effect on gonad weight when LH and FSH were given simultaneously, and only a questionable synergism was observed between the 2 hormones with respect to P³² uptake. A comparison was made between the action of the N.I.H. ovine hormones and Armour equine LH (Lot R377279) and equine FSH (Lot R377236). The Armour LH was much less potent (per μg) than was the N.I.H. preparation; however, the Armour FSH was more effective (per μg) than the N.I.H.-FSH. The P³² assay was very effective in determining the gonadotropin content of acetone-dried anterior pituitary glands of cockerels. Dosages as low as 0.30 mg equivalent of fresh gland (approximately 1/20 of a pituitary) caused marked increases in P³² uptake. Significant differential responses were observed between uptakes in testes which received pituitaries of 170- and 75-day-old donors.