Evaluation of LH secretory dynamics during the rat proestrous LH surge

The preovulatory luteinizing hormone (LH) surge results from the integratio n of complex interactions among gonadal steroids and hypothalamic and pitui tary hormones. To evaluate changes in LH secretory dynamics that occur duri ng the rat LH surge, we have 1) obtained frequently sampled serum LH concen tration time series, 2) used both waveform-dependent and waveform-independe nt convolution analyses, and 3) independently assessed proestrous LH half-l ife and basal non-gonadotropin-releasing hormone (GnRH)-dependent LH secret ion during the LH surge. Waveform-independent pulse analysis revealed a 24- fold increase in the maximal pulsatile LH secretory rate attained during la te proestrus compared with early proestrus. A 15-fold increase was quantifi ed for the mean LH secretory rate. In complementary analyses, we applied a measured LH half-life of 17 +/- 2.7 min and a median basal LH secretion rat e of 0.0046 mu g.l(-1.) min(-1) for convolution analysis, revealing a 16-fo ld increase in the mass of LH released/burst and more than sixfold rise in the amplitude of the secretory peaks. Evaluation of the approximate entropy of the LH surge profiles was performed, showing an increase in the orderli ness of the LH release process during the surge. We conclude that both quan titative (mass/burst) and qualitative (approximate entropy) features of LH release are regulated during the proestrous LH surge.