Functional LH receptor appears in the neonatal rat ovary after changes in the alternative splicing pattern of the LH receptor mRNA.

The LH receptor (R) function, as assessed by ligand binding and stimulation of cAMP production, is initiated in the neonatal rat ovary around day 7 of life. To correlate this with the onset of expression of the LHR gene, we assessed the presence of the cognate mRNA in the developing rat ovary from day 17 of fetal life onwards using PCR multiplication of reverse transcribed LHR mRNA, followed by southern hybridization and sequencing of the PCR products. Our findings indicate that only truncated versions of LHR mRNA are present in the developing rat ovary as early as day 17 fetal life and up to day 7 post partum. Concomitant with the appearance of a functional LH receptor (after day 7 post partum), two larger LHR mRNA species (2.6 and 6.7 kb) appear, which are also present in the adult ovary. These findings indicate that the LHR gene is probably constitutively expressed in the developing rat ovary, and that the onset of translation of functional LH receptor occurs through a change in the alternative splicing pattern of LHR mRNA.