Oral Presentation The Annual Scientific Meeting of the Endocrine Society of Australia and the Society for Reproductive Biology 2014

Luteinizing Hormone (LH) and Growth hormone (GH) pulsatile profiles in female and male mice across reproductive stages: advanced incorporation of transgenic mouse lines (#131)

Chen Chen , Y Wan 1 , J Steyn 1 , J D Veldhuis 2
  1. School of Biomedical Sciences, University of Queensland, St Lucia, Qld 4072, Australia
  2. Endocrine Research Unit, Mayo Clinic College of Medicine, Centre for Translational Science Activities, Mayo Clinic, Rochester, MN, USA

Sexual development and linear growth are modulated through the coordinated maturation of the hypothalamic-pituitary-gonadal (HPG) and -somatic (HPS) axes. The introduction of reliable methodologies that allow repeat assessment of pulsatile growth hormone (GH) and luteinizing hormone (LH) release in mice has provided renewed opportunities to use existing transgenic lines to define the regulation of release and function of these hormones. However, comparative measures of pulsatile LH and GH profiles in pubertal and early adult female and male mice do not exist. To address this, we monitored pulsatile LH and GH release in female and male C57Bl6 mice relative to age and reproductive function. In females, LH measures were compared from the first ovulatory cycle (5 weeks old) to that seen in adult mice (10 weeks old). We observed significant changes in the pattern of LH release across the estrous cycle, characterized by an increase in pulse number and irregularity from estrus to diestrous. Altered pulse dynamics was matched with a decrease in the mass of LH secretion per pulse. Pulse dynamics of the first and adult ovulatory cycles were well conserved, and defined by a rise in pulse number and irregularity at diestrous only. The amplitude of the LH surge was conserved between 5 and 10 weeks of age. For GH, we documented significant changes in pulse dynamics between female and male mice. GH in females was characterized by an increase in pulse frequency, irregularity, and basal release. This change in pulse dynamics persisted throughout the estrous cycle. Of interest, we observed a significant rise in total, pulsatile and mean peak per pulse of GH at proestrous. This occurred alongside the preovulatory LH surge. Observations provide essential information to define hypothalamic control of LH and GH release in mice, and set the premise for future studies using transgenic lines.