Intratesticular tissue fluid (ITF) for the micro-bioassay of LH

Intratesticular tissue fluid (ITF) was obtained by centrifugation of the decapsulated testis of the adult rat. Testosterone level in ITF was increased by direct injection of LH into the testis and was lowered by anti-LH serum. Based on the result of previous reports with testosterone in testicular vein blood, a simplification of the LH bioassay without imparing sensitivity and accuracy was undertaken using ITF as the material for testosterone measurement. Dose-response relationship between injected LH and testosterone concentration in ITF was observed. The sensitivity of the assay was 5 ng for LH (NIH-LH-S15). FSH (NIH-FSH-S10) and prolactin (NIH-P-S11) had no detectable activity on testosterone production. This assay method depending on biological activities of LH will be helpful for unbiased evaluation of the result obtained by radioimmunoassay.