Radioimmunoassay and LH Pulse Parameter Analysis.

Plasma LH concentrations were determined by a double-antibody radioimmunoassay (RIA) with a rat LH-RIA kit provided by the National Hormone and Peptide Program (NHPP). The concentrations were expressed in terms of rat LH-RP3. The least detectable level of LH assay was 3.9 pg/tube, and the intra- and interassay coefficients of variation were 4.3 and 9.1% at 69 pg/tube, respectively. LH pulses were identified by the PULSAR computer program (61). Mean LH concentration and the frequency and amplitude of LH pulses were calculated during the 3-h sampling period for each individual and then for the group. As for the E2-induced LH surge, a ratio of peak to baseline of LH surge was calculated in each individual and then in the group.

The pituitary LH and FSH content were also determined by RIA with rat LH-RIA and rat FSH-RIA kits. The fixed hemipituitaries were homogenized and sonicated in RIA buffer (0.05 M phosphate-buffered saline) and LH and FSH concentrations in the supernatant were determined. The FSH concentrations were expressed in terms of the rat FSH-RP2. The least detectable level of FSH assay was 15.6 pg/tube, and the intra- and interassay coefficients of variation were 5.8 and 7.2% at 564 pg/tube, respectively.