Time-of-flight secondary ion mass spectrometry can replace histochemistry demonstration of fatty acids in the retina.

Abstract

The purpose of this study was to demonstrate fatty acids in the rat retina and to show that time-of-flight secondary ion mass spectrometry (TOF-SIMS) can replace histochemistry. Five normal 3-month-old Wistar Kyoto rats were used. The eyes were enucleated under pentobarbital anesthesia, immediately put into liquid nitrogen without any fixation, then cut into semithin sections, which were covered by OCT compound. Serial semithin sections were cut to 8- micro m thickness with a cryoultramicrotome and air-dried. They were placed on a silicon plate and air-dried for 1 h for analysis with TOF-SIMS. Before the specimens were analyzed, the molecular weight of the secondary ion for each molecular substance was measured with the use of commercial samples. These values were used for calculating the count of the secondary ion for each molecular substance. The molecular weights of the secondary ions of maleic acid, palmitic acid, oleic acid, stearic acid, arachidonic acid, and docosahexaenoic acid were determined in the photoreceptor cells. Of the fatty acids in the photoreceptor cells, maleic acid had the highest count, followed in descending order by palmitic, oleic, docosahexaenoic, stearic, and arachidonic acids. TOF-SIMS can demonstrate the presence of fatty acids in the retina, replacing histochemical techniques.