Enhancing effect of acute fasting on ethanol suppression of pulsatile luteinizing hormone release via an estrogen-dependent mechanism in Holstein heifers.

摘要

The objectives of this study were (1) to determine whether acute fasting increases the suppressive effect of ethanol on pulsatile LH release and (2) to establish whether the mechanism is oestrogen-dependent. 29 heifers were synchronized in oestrus (day 0 = day of oestrus) and were fasted or fully fed (controls) from day 1 to day 4. On day 4, blood samples were taken at 10-min intervals for 4 h before (preinjection) and after (postinjection) an intravenous injection of 1.5 ml of saline, 1.5 ml ethanol or 35 mg tamoxifen dissolved in 1.5 ml ethanol. The groups were compared for the mean LH level, the number of LH peaks per 4 h and the amplitude of LH peaks. The control and fasting groups did not differ in any of the LH parameters during the preinjection period. In the postinjection period, the control/ethanol heifers had fewer LH peaks than control/saline heifers (P<0.05). In the fasting/ethanol group, all 3 LH parameters were lower (P<0.01) than in the other 2 fasting groups. Tamoxifen inhibited the suppression of LH by ethanol in control and fasting heifers.