In order to assess the impact of mRNA degradation on steady state levels of follicle stimulating hormone receptor (FSHR) mRNA and on regulation of FSHR gene expression, the stability and half life of FSHR mRNA were determined in transfected cells expressing recombinant FSHR. Time dependent changes in FSHR mRNA content were determined by nuclease protection solution hybridization assay (NPA) or by qualitative reverse transcription competitive polymerase chain reaction (RT PCR) in cultured hFSHR YI cells, cell lines stably transfected with a human FSHR cDNA. FSHR mRNA content remained constant during 8 h control incubations of hFSHR Y1 cells (NPA, 2.9±0.3 μg/mg RNA; RT PCR, 2.7±0.3 μg/mg RNA). Actinomycin D (ActD, 5 μg/ml) inhibited mRNA synthesis, as assessed by incorporation of uridine into total RNA, by 90 % within 1 h in hFSHR Y1 cells. No effect of ActD on cellular morphology or viability was observed. ActD caused a time dependent decrease in FSHR mRNA content in hFSHR Y1 cell lines with a lag time of 1 h. There were no significant differences in the rate of FSHR mRNA degradation between the two methods of mRNA quantification. The half life of hFSHR mRNA was 3.6±0.2 h by NPA and 3.1±0.1 h by RT PCR. The results indicated that degradation of mRNA was an important process in maintenance of steady state expression of the FSHR gene in cells stably expressing recombinant receptor. In order to assess the impact of mRNA degradation on steady state levels of follicle stimulating hormone receptor (FSHR) mRNA and on regulation of FSHR gene expression, the stability and half life of FSHR mRNA were determined in transfected cells expressing recombinant FSHR. Time dependent changes in FSHR mRNA content were determined by nuclease protection solution hybridization assay (NPA) or by qualitative reverse transcription competitive polymerase chain reaction (RT PCR) in cultured hFSHR YI cells, cell lines stably transfected with a human FSHR cDNA. 8 h control incubations of hFSHR Y1 cells (NPA, 2.9 ± 0.3 μg / mg RNA; RT PCR, 2.7 ± 0.3 μg / mg RNA) Actinomycin D (ActD, 5 μg / ml) inhibited mRNA synthesis, as assessed by incorporation of uridine into total RNA, by 90% within 1 h in hFSHR Y1 cells. No effect of ActD on cellular morphology or viability was observed. ActD caused a time dependent decrease in FSHR mRNA content in hFSHR Y1 cell lines with a lag time of 1 h. There were no significant differences in the rate of FSHR mRNA degradation between the two methods of mRNA quantification. The half life of hFSHR mRNA was 3.6 ± 0.2 h by NPA and 3.1 ± 0.1 h by RT PCR. The results indicated that degradation of mRNA was an important process in maintenance of steady state expression of the FSHR gene in cells stably expressing recombinant receptor.