Submitted to: Journal of Endocrinology
Publication Type: Abstract Only
Publication Acceptance Date: 4/2/1997
Publication Date: N/A
Technical Abstract: Estradiol-17b (E2) is known to enhance the LH response of AP cells to GnRH through a variety of mechanisms. One possible mechanism may involve dynporphin, a stress-related peptide which is colocalized with LH in the gonadotrophs. The present work validated a suspension culture for dispersed bovine AP cells wherein these effects of E2 could be demonstrated din order to measure concurrent changes in mRNA for LH-b-subunit (LH-b), an prodynorphin. AP cells from castrated bovine males were enzymatically dispersed and cultured for 24 h to 46 h before exposure to various dosages of E2 (0.04 to 40 nM) for an additional period of 2 h, 10 h, or 24 h. Following the period of E2 exposure and at 48 h after dispersion, some cells were exposed to various dosages (0.1 to 100 nM) of GnRH for 2 h. Dynorphin release into culture medium was not affected by GnRH but was increased by E2 in both dosage- and time-dependent tmanner with lower E2 dosages requiring longer exposure for significant release to occur. However, there was no situation wherein mRNA for prodynorphin was increased by E2 exposure suggesting that non transcriptional mechanisms were involved in the E2-induced release of dynorphin. The dosage sensitivity of LH release induced by GnRH was greater for 24 h than for 10 h periods of E2 exposure, and a 2 h period of E2 exposure had no significant effect on AP sensitivity to GnRH. However, mRNA for LH-b was increased (P<.05) by E2 exposure lasting 10 h but not 24 h. The present results demonstrate that E2 augmentation of LH and dynorphin release from bovine AP cells can be independent of effects on transcription of the genes studied in this experiment.