Age-dependence of the lateral diffusion coefficient of lipids and proteins in the hepatocyte plasma membrane of BN/BiRijHsd rats as revealed by the smear-FRAP technique

Abstract

The lateral diffusion coefficients of lipids ( D l) and proteins ( D p) were measured in hepatocyte plasma membranes in freshly prepared liver smears of Brown Norway (BN/BiRijHsd) rats by means of the fluorescence recovery after photobleaching (FRAP) method. D l was measured after staining with N-4-nitrobenzo-2-oxa-1,3-diazolyl phosphatidylethanolamine (NBD-PE) in 14 males in four age groups (4.3–30.4 months), and 12 females (5.0–31.0 months). D p was measured after the development of peroxide-induced autofluorescence (PIAF) in 16 males in four age groups (4.7–30.8 months) and 15 females in four age groups (4.0–28.1 months). Highly significant negative, linear age-correlations of D l (R=−0.972 in males, and −0.840 in females, respectively) were found, the average data being 1.39×10 −9 cm 2/s in the young male rats, and only 9.26×10 −10 cm 2/s in the oldest ones, whereas in females, these two extremes were 1.44×10 −9 and 8.97×10 −10 cm 2/s, respectively. Protein lateral mobility also declined linearly with age; in the male rats it decreased from 2.7×10 −10 to 1.8.×10 −10 cm 2/s (R=−0.903), while in the females it decreased from 2.64×10 −10 to 2.21×10 −10 cm 2/s (R=−0.955) between the youngest and oldest age groups. There were also some characteristic differences in the fractional recoveries (FR%), too. These trends are comparable with those of F344 rats studied previously, supporting the conclusion that the changes in the lateral mobility of plasma membrane proteins and lipids represent important biomarkers of cellular aging also in the BN/BiRijHsd rats.