Male @entity1707 fetuses secrete considerable amounts of @entity172 , but the location of aromatase activity within the fetal testis is not known. The location of aromatase expression was investigated by immunocytochemistry in fetal testes from week 6 (n = 5), weeks 10, 13, and 15 (each: n = 6) of gestation and additionally in neonates (n = 4). Blood was sampled from the umbilical artery of fetuses and jugular vein of neonates. Histological evaluation of testes involved morphological criteria and counting of Leydig cells, Sertoli cells, and gonocytes. Aromatase activity was localized immunocytochemically and quantified by the percentage of positive stained cells within the same cell type. Aromatase expression was further characterized by quantitative RT-PCR. Concentrations of @entity172 , @entity251 , FSH, and LH were measured in blood plasma. Total @entity172 increased from week 10 to a maximum of 31.03 nmol/l in week 15. Increased @entity251 concentrations were only measured at week 6 and were paralleled by slightly elevated @entity172 . Thereafter, @entity251 dropped and was low throughout. The increase of @entity172 was not paralleled by a similar increase of FSH and LH but was related to the increase of the total number of Leydig cells. This increase was also found for mRNA expression. Both Leydig cells and gonocytes were identified as contributors to @entity172 formation. Gonocytes were the main source of aromatase at week 10, when gene expression by Leydig cells is low due to the preparation of a wave of Leydig cell mitosis.

Changes of testicular aromatase expression during fetal development in male XXXX ( @entity1707 ).

@entity172 :: ('MESH:D004967', 'Chemical') :: ['estrogen', 'estrogens'] @entity1707 :: ('9823', 'Species') :: ['pig'] @entity251 :: ('MESH:D013739', 'Chemical') :: ['testosterone']
@entity1707 :: (9823,Species) :: ['pigs']
