Choroid epithelial cells: source cerebrospinal fluid progesterone in sheep?

The present study was conducted to immunolocalize 3b-hydroxysteroid dehydrogenase (3β-HSD), an enzyme metabolizing pregnenolone to progesterone in the choroid plexus of the lateral ventricle in sheep, as well as to measure progesterone concentration in cerebrospinal fluid (CSF) and plasma using radioimmunoassay (RIA). Akkaraman breed rams (n = 16) and ewes (n = 16) were utilized in the study. 3β-HSD was immunolocalized in choroid epithelial cells of the choroid plexus with an apparent cytoplasmic immunoreactivity. Progesterone was detected in CSF with no significant differences between the ewes (0.76 ± 0.14 ng/mL) and rams (0.74 ± 0.13 ng/mL) (p > 0.05). However, the plasma progesterone concentration in the ewes (0.27 ± 0.04 ng/mL) was significantly higher than that of the rams (0.11 ± 0.02 ng/mL) (p < 0.001). Consequently, CSF in sheep contains progesterone in significant levels. As evidenced by 3β-HSD immunoreactivity, choroid epithelial cells may be a site of progesterone synthesis in sheep.