MORPHOMETRIC STUDY OF THE GUBERNACULUM IN MALE ESTROGEN-RECEPTOR MUTANT MICE

To determine role of estrogen receptors in testicular descent, a morph ometric study of the testis and structures derived from the gubernacul um was made in sexually mature male mice having an estrogen receptor d isrupted gene mutation (ERKO). Macroscopic dissections and sagittal se rial sections were made of the pelvis of four wild-type mice, four mic e heterozygous for the ERKO mutation, and four homozygous ERKO males. By external morphological examination the testes appeared to be descen ded in all three genotypes. All mice had development of a cremaster sa c, which is derived from the gubernaculum, but this was twice as large in wildtype mice than in both the heterozygote or homozygote ERKO gro ups. The cause for the smaller cremaster sac appeared to be excessive development of the cremaster muscle in ERKO mice. The thickened muscle was associated with postmortem retraction of the testes into the ingu inal canal or abdomen. Spermatogenesis and testicular volume were defi cient in homozygous ERKO mice at this age. This study demonstrates tha t estrogen has a previously unknown role in masculine sexual developme nt of the gubernaculum and the structures derived from it, such as the cremaster muscle.