Time-of-flight secondary ion mass spectrometry of fatty acids in rat retina

Abstract

The retina consists of many kinds of central nervous cells, and some cells contain fatty acids such as palmitic acid, stearic acid and oleic acid. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has a possibility to detect kinds and quantity of materials in relation to the cell or tissue. We applied TOF-SIMS to detect the palmitic acid, stearic acid and oleic acid in the visual cell of the rat retina. We used 4- and 18-month-old normal Wistar Kyoto rats. After pentobarbital anesthesia, the eyes were enucleated, and immediately put into liquid nitrogen without any fixation and then cut into semithin sections (10 μm) with a cryo-ultramicrotome, and laid it on a silicon wafer plate and air-dried. Ion images were detected with TOF-SIMS. Positive ion images were examined with a Ga + source at an acceleration voltage of 15 keV. The secondary ion acceleration voltage was 4.5 keV. In the 4-month-old rat, palmitic and stearic acid were detected in the photoreceptor outer segment and nuclear parts, but not in the inner segment. In the 18-month-old rat, the oleic acid is significantly decreased compared to that in the 4-month-old rat. TOF-SIMS is a useful tool to detect the changes of fatty acids corresponding to changes of physiological conditions in relation to the histological features.