Free and esterified cholesterol in developing feline white matter

The content of free and esterified cholesterol was examined in the cervical spinal cord lateral funiculus and in the corpus callosum of the cat during postnatal development. The concentration of free cholesterol increased with development from 8 to 56 μg/mg in the lateral funiculus and from 4 to 37 μg/mg in the corpus callosum. The total content per specimen increased 130 and 70 times, respectively. The major part of the postnatal increase in the free cholesterol occurred late postnatally. The concentration of esterified cholesterol decreased with development from 0.96 to 0.07% and from 9.50 to 0.30% of total sterol in the lateral funiculus and corpus callosum, respectively. In both regions, the total content per specimen increased with maturation. Throughout development, the content of cholesteryl ester was higher in the corpus callosum than in the lateral funiculus. A transient increase in esterified cholesterol concentration was seen during the first postnatal days in the lateral funiculus and 3 weeks postnatally in the corpus callosum. The results suggest that most of the postnatal increase of free cholesterol in the white matter is related to a continued growth of established myelin sheaths and not to de novo myelination. The transient increase in concentration of esterified cholesterol in the early postnatal lateral funiculus coincides in time with a spontaneous myelin sheath disintegration. This supports the view that the ester peak may be primarily related to myelin breakdown rather than to myelin production. The significance of the high ester concentration in the neonatal corpus callosum and the ester peak seen during initial myelination remains obscure and calls for further developmental morphological studies.