EXPRESSION OF MULTIPLE THYROID-HORMONE RECEPTOR MESSENGER-RNAS IN HUMAN OOCYTES, CUMULUS CELLS, AND GRANULOSA-CELLS

Thyroid hormones have diverse effects on ovarian function. We examined the expression of thyroid hormone receptor (TR) mRNAs (including TR a lpha-1, TR beta-1, TR beta-2, and c-erbA alpha-2 isoforms) in three ty pes of cells from human follicles, and determined the concentration of free tri-iodothyronine (T-3) present in human follicular fluid. Human failed-fertilized oocytes, granulosa (GC) and cumulus (CC) cells from patients of the in-vitro fertilization (IVF) programme at Alliant Hos pital Fertility Center were used to detect TR mRNA expression using re verse transcription-polymerase chain reaction (RT-PCR) followed by Sou thern blot analysis. Human spermatozoa were also analysed to determine whether results obtained with CC would be affected by the presence of spermatozoa. beta-Actin mRNA was amplified in each cell type as a pos itive control for the RT-PCR. Our results show that human oocytes expr ess TR alpha-1, TR beta-1, TR beta-2, and c-erbA alpha-2 mRNAs and tha t these same isoforms are expressed in both human granulosa cells and cumulus cells. No differences were detected in the apparent amounts of RT-PCR products when comparing GC with CC, suggesting a similar patte rn of expression of these RNAs. beta-actin mRNA was detected in sperma tozoa, but TR alpha-1 expression was not detectable. The concentration s of free T-3 measured in follicular fluid were similar to, or slightl y below, those in serum of euthyroid patients. These data demonstrated that several isoforms of TR mRNA are expressed in the human oocyte, a nd hence thyroid hormone may have direct affects on the oocyte, as wel l as on GC and CC. In addition thyroid hormone may have indirect effec ts on the oocytes via the CC.