Differential regulation of pituitary gonadotropin subunit messenger ribonucleic acid levels in photostimulated Siberian hamsters

Daniel J. Bernard*, Irene Y. Merzlyak, Teresa H. Horton, Fred W. Turek

*Corresponding author for this work

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

FSH levels begin to rise 3-5 days after male Siberian hamsters are transferred from inhibitory short photoperiods to stimulatory long photoperiods. In contrast, LH levels do not increase for several weeks. This differential pattern of FSH and LH secretion represents one of the most profound in vivo examples of differential regulation of the gonadotropins. The present study was undertaken to characterize the molecular mechanisms controlling differential FSH and LH synthesis and secretion in photostimulated Siberian hamsters. First, we cloned species-specific cDNAs for the three gonadotropin subunits: the common α subunit and the unique FSHβ and LHβ subunits. All three subunits share high nucleotide and predicted amino acid sequence identity with the orthologous cDNAs from rats. We then used these new molecular probes to examine the gonadotropin subunit mRNA levels from pituitaries of short-day male hamsters transferred to long days for 2, 5, 7, 10, 15, or 20 days. Short-day (SD) and long-day (LD) controls remained in short and long days, respectively, from the time of weaning. We measured serum FSH and LH levels by RIA. FSHβ, LHβ, and α subunit mRNA levels were measured from individual pituitaries using a microlysate ribonuclease protection assay. Serum FSH and pituitary FSHβ mRNA levels changed similarly following long-day transfer. Both were significantly elevated after five long days (2.3- and 3.6-fold, respectively; P < 0.02) and declined thereafter, but they remained above SD control values through 20 long days. Alpha subunit mRNA levels also increased significantly relative to SD control values (maximum 2-fold increase after seven long days; P < 0.03), although to a lesser extent than FSHβ. Neither serum LH nor pituitary LHβ mRNA levels changed significantly following long-day transfer. The results indicate that long-day-associated increases in serum FSH levels in Siberian hamsters reflect an underlying increase in pituitary FSHβ and α subunit mRNA accumulation.

Original languageEnglish (US)
Pages (from-to)155-161
Number of pages7
JournalBiology of reproduction
Volume62
Issue number1
DOIs
StatePublished - Jan 1 2000

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ASJC Scopus subject areas

  • Reproductive Medicine
  • Cell Biology

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