FSH stimulation of testicular androgen binding protein (ABP): comparison of ABP response and ovarian augmentation.

Production of testicular androgen binding protein (ABP), ceases following hypophysectomy and can be stimulated by FSH. Within 24 h after the administration of FSH, ABP can be measured in caput epididymis supernatant and by 4 days after FSH treatment, the concentration of ABP reaches a plateau. In a 3-day assay, ABP production in immature hypophysectomized rats was stimulated by 31 mug NIH-FSH-P1 per day (0.08 U NIH-FSH-P1 per 3 days) which is comparable to the sensitivity of the ovarian weight augmentation test in hypophysectomized rats. The relative ovarian weight augmenting and ABP stimulating activities of various FSH preparations were in agreement, suggesting that the biological stimulus of the ABP response is, in fact, FSH. The ABP response to FSH could become a useful testicular bioassay for FSH. Such an assay would be more practicle if ABP could be measured by a radioimmunoassay.