DIFFERENCES in PLASMA CONCENTRATIONS of LH and FSH in ANOESTRUOUS EWES TREATED with GnRH or a GnRH ANALOGUE

Abstract

This study was conducted using 16 anoestrous ewes to determine the effects of GnRH or an analogue of GnRH (A-N; Azagly-nafarelin; Intervet International BV, Boxmeer, The Netherlands) on secretion of LH and FSH.  In the experiment, 7 treatments were used over 16 days in a randomised Latin square design. The treatments were saline, GnRH (0.1, 1 and 10 µg) or A-N (0.001, 0.01, 0.1 and 1 µg), desolved in 2ml saline then injected intravenously. Blood samples were collected at intervals of 15, 30 or 60 min from 60 min before until 360 min after the injection. In the experiment jugular venous blood was collected from an indwelling jugular venous catheter. The sensitivities of LH and FSH assays were 0.22±0.01 ng/ml and 0.055± 0.005 ng/ml respectively. For LH assay, intra-assay coefficient of variations for high, medium and low were 10.5, 11.1 and 11.4 and inter-assay coefficient of variation for high, medium and low were 20.2, 10.5 and 16.2, respectively. For FSH assay, inter-assay coefficient of variations for high, medium and low were 7.4, 7.6 and 12.0 and intra-assay coefficient of variations, or high, medium and low, were 4.8, 16.9, and 17.9, respectively.

         According to the data, small doses of GnRH or A-N did not significantly effect plasma concentrations  of FSH and LH , whereas higher doses of GnRH (10mg) and of A-N (1.0 mg) caused a significant increase in plasma FSH and LH concentrations. In addition, it has been seen that the A-N was 30 and 38 times more potent than GnRH for the induction of FSH and LH secretions, respectively.