Vitamin D (Soltriol) receptors in the choroid plexus and ependyma: Their species-specific presence

Abstract

The present study describes the appearance of high-affinity nuclear binding sites (receptors) for 1,25-dihydroxyvitamin D 3 (soltriol) in organs that contribute to the blood-brain barrier such as choroid plexus and ependyma in the Djungarian hamster Phodopus sungorus, C57BL/6J mice, and vitamin D-deficient Sprague-Dawley rats. Using autoradiography, after injection of 1,25[ 3H]dihydroxyvitamin D 3 specific nuclear neuronal labeling is seen in all species in certain regions of the brain. Choroid plexus and ependyma show distinct species differences. In female and male Phodopus, constantly raised under long-day conditions or transferred for S weeks to a short-day cycle, nuclear receptors for 1,25-dihydroxy-vitamin D 3 are present in the choroid epithelium of all ventricles, while nuclear labeling is inconspicuous or absent in nonepithelial cells of the choroid plexus and most of the ependyma. Some ependymal cells in select regions of all ventricles display nuclear labeling that includes portions of the lateral ventricle, ventral and dorsal third ventricle, aqueduct, and fourth ventricle, but is comparatively weak. Differential presence of radioactivity in ventricular regions was noted, suggesting binding to proteins in cerebrospinal fluid. In mice and rats nuclear binding is absent or inconspicuous in choroid epithelium and ependyma under conditions when strong nuclear labeling is present in neurons of the nucleus centralis of the amygdala and cranial motor nerve nuclei. Vitamin D synthesis is dependent on sunlight and its levels change with season. Therefore, it is suggested that vitamin D (soltriol) regulates functions of choroid plexus and ependyma in the Djungarian hamster, probably thus serving the transmission of circannual changes in rodent species with strong seasonal adaptations.