Rat intratesticular test systems for investigating luteinizing hormone releasing factor (LRF) and luteinizing hormone (LH) activities: effects of rat stalk-median eminence extract and internal environment of rat testis upon rat and quail anterior pituitaries.

Abstract

New test systems for evaluating LH and LRF activities using a combined local techniques of rat testis were presented.A response brought by intratesticularly injected LH was assessed by testosterone output in the testicular vein blood (TVB). A significant rise in testosterone output was obtained with 5 ng of NIH-LH-S15 and 1/5, 000 gland equivalent dose of rat pituitary extract. As a sensitive bioassay for LH, this test system seems promising.For investigating LRF activity, a rat stalk-median eminence extract (rSME) was locally infused into the testis bearing rat or quail pituitary implant. LH contents in pituitaries of pre-and post-implantation (2 hr) were measured by intrabursal OAAD test for evaluating a direct effect of LRF, and at the same time the indirect effect due to the released LH from the implanted pituitary, was assessed by the increase of testosterone in TVB. Effects of intratesticular implantation of pituitary alone on these two parameters were also investigated.It was noteworthy that the internal medium of rat testis induced a striking LH release from the rat pituitary, but not from the quail pituitary. A factor (s) other than ionic components in the testis (tentatively named as ITLR) may be responsible for this release.Upon the quail pituitary, rSME mainly manifested the LH releasing activity. Although the LH releasing activity of rSME on the rat pituitary was overshadowed due to concurrent action of ITLR in this intratesticular test system, the stimulatory effect of rSME on the LH production was clearly indicated.Species specificity and action mode of LRF were discussed from these findings.