Abstract
Abstract: :
Purpose: To determine the extent of commonality in the phospholipid composition of membranes from non-human primate lenses and to test the hypothesis that the relative amounts of dihydrosphingomyelins (DHSMs) correlate with lens growth rates. Methods: Lenses of a prosimian primate, a black lemur (20 y.o., 380 mg/lens), and of New World primates, two woolly monkeys of different ages (10 y.o., 84 mg/lens, and 22 y.o., 97 mg/lens) were dissected into cortical and nuclear regions. Phospholipids were obtained from each fraction with a single-step methanolic extraction. The lipid-containing supernatants were analyzed by 31P NMR spectroscopy using a CsOH/EDTA reagent that enhances the resolution of the phospholipid bands. Results: The relative amounts of DHSMs in the lenses investigated herein were greater than in any other non-primate mammalian lens but smaller than in human lenses. For each primate lens, the relative levels of phosphatidylcholines (PCs) and PC plasmalogens were greater in the cortex than in the nucleus. Furthermore, the levels of these glycerolipids were highest in the cortical membranes of the youngest primate investigated in this study (20% in 10 y.o. woolly monkey) and undetectable in the nuclei of the older primates. Among other phospholipids, sphingomyelins (SMs) and DHMSs were the most abundant. Their combined relative content extended from 44% of all phospholipids in the cortex of the lemur to more than 90% in the nuclei of the older monkeys. With an overall average of 0.81 ± 0.29 in the ratios of DHSMs to SMs, membranes from woolly monkey lenses were richer in DHSMs than those of the lemur lenses (DHSMs/SMs = 0.26 ± 0.11). Conclusions: The relative levels of DHSMs were higher in the lenses of woolly monkeys than in those of the lemur. These primates have similar life spans (20 to 25 years), but the lifetime-averaged growth rate of woolly monkey lenses is slower than that of the black lemur. These findings, in conjunction with previous results obtained for human and other mammalian lenses support the correlation between high levels of DHSMs and slow growth rates in mammalian lenses.
Keywords: cell membrane/membrane specializations • lipids • aging