Failure of shortening and inversion of the perinatal gubernaculum in the cryptorchid Long-Evans orl rat

Purpose: Failure of testicular descent occurs in about 65% of spontaneously cryptorchid Long-Evans orl rats. Development of the fetal gubernaculum is dependent on expression of leucine rich G protein coupled receptor (also known as G protein coupled receptor affecting testicular descent) and its ligand, insulin-like 3. We studied testicular descent and mRNA expression of insulin-like 3 and leucine rich G protein coupled receptor in Long-Evans orl and Long-Evans wild-type rats during perinatal development. Materials and Methods: Long-Evans orl and Long-Evans wild-type males obtained at gestational days 18 to 21 and day of birth were preserved in RNAlater@ for at least 24 hours. The size and position of the testes, kidneys and gubernacula were determined by microdissection and image analysis. Leucine rich G protein coupled receptor mRNA expression was analyzed in fetal gubernacula (gestational days 18 to 21) using real-time reverse transcriptase polymerase chain reaction with SYBR (R) Green detection. Insulin-like 3 mRNA expression in fetal testis (gestational days 18 and 20) was determined by semiquantitative reverse transcriptase polymerase chain reaction. Results: Testicular position was similar in Long-Evans orl and Long-Evans wild-type fetal rats. However, gubernacula were narrow (p < 0.001) and elongated (p <= 0.01) in Long-Evans orl compared to Long-Evans wild-type fetuses at all time points. Inversion of both gubernacula occurred by the day of birth in 45% of Long-Evans orl and 100% of Long-Evans wild-type males (p < 0.001). Leucine rich G protein coupled receptor mRNA expression decreased with age and, similar to insulin-like 3 mRNA, was not consistently different between strains. Conclusions: These data suggest that the impaired shortening of the Long-Evans orl gubernaculum may interfere with the timing and quality of its inversion at birth, leading to failure of testicular descent in some newborn males. However, fetal testicular descent and the expression of leucine rich G protein coupled receptor and insulin-like 3 mRNA appear to be normal in this strain.