Plasma 17 beta-estradiol levels and ovarian interstitial cell structure inembryonic Japanese quail

Plasma concentrations of 17 beta-estradiol (E-2) and left ovarian histology were investigated by light and electron microscopy in female Japanese quai l from Day 10 of embryonic development through Day 7, posthatch. Plasma E-2 levels remained relatively constant (102 to 140 pg/mL) in the embryo follo wed by a sharp decrease posthatch (47 to 70 pg/mL). Beginning on Day 10 of incubation, cells in the medullary portion (medullar y cell; MC) of the left ovaries exhibited ultrastructural evidence of stero idogenic capability. The MC had numerous lipid droplets in close proximity to the smooth endopla smic reticulum (SER). Mitochondria were also observed in the vicinity of th e lipid droplets and SER. On Days 10 and 12, the cristae of the inner mitoc hondrial membranes were of a lamellar configuration; the cristae of some mi tochondria in MC had a tubular appearance by Day 14. These data document re lative ontogenic changes in ovarian morphology and plasma E-2 levels during the early developmental period in female Japanese quail. These data furthe r support the role of this steroid in sexual differentiation.