Sexual and developmental differences in peptides regulating growth hormone secretion in the rat

Steven M. Gabriel, William J. Millard, James I. Koenig, Thomas M. Badger, William E. Russell, Dominique M. Mailer, Joseph B. Martin

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

Sex differences in the hypothalamic control of growth hormone (GH) secretion were investigated by measuring rat GH-releasing factor (rGRF) and somatostatin in male and female rats. Rat GRF-like immunoreactivity (rGRF-IR) was higher in the median eminence and hypothalamic tissue outside of the median eminence of adult (90-day-old) male compared to female rats. A similiar pattern of rGRF-IR content was found in the median eminence of 35-day-old rats. This sex difference developed between days 25 and 35 of age. during which time serum concentrations of insulin-like growth factor (IGF-1) and body weight increased in both sexes. To a lesser extent, the content of somatostatin-like immunoreactivity (SLI) was higher in the median eminence of adult female rats compared to male rats. Whole hypothalamic rGRF-IR and SLI contents were influenced only moderately by adult gonadectomy or gonadal steroid treatments. For example, estrogen increased rGRF-IR content in castrated rats, but orchidectomy alone or orchidectomy followed by testosterone did not influence rGRF-IR content. Additionally, whole hypothalamic SLI content was unaffected by orchidectomy or orchidectomy followed by testosterone or estrogen. One month after ovariectomy, rGRF-IR and SLI in whole hypothalamic fragments were similar to their respective contents in gonad-intact males. However, ovariectomy followed by estrogen or testosterone did not restore rGRF-IR content and partially restored SLI content to levels seen in gonad-intact females.

Original languageEnglish
Pages (from-to)299-307
Number of pages9
JournalNeuroendocrinology
Volume50
Issue number3
DOIs
StatePublished - 1989
Externally publishedYes

Keywords

  • Estrogen
  • Gonadal steroids
  • Growth hormone
  • Growth hormone-releasing factor
  • Hypothalamus
  • Sex difference
  • Somatostatin
  • Testosterone

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