Age- and gender-related differences in carbohydrate concentrations of alpha1-acid glycoprotein variants and the effects of glycoforms on their drug-binding capacities.
OBJECTIVE
Alpha(1)-acid glycoprotein (AAG) is a major binding protein for neutral and basic drugs because of its great drug affinity. AAG has three main genetic variants--F1, S, and A variants. Several attempts have been made to elucidate the differences in compositions of the carbohydrate moiety and structure-function relationships such as drug-binding differences. However, there have been few reports on age- and gender-related differences in compositions or concentrations of the carbohydrate moiety of AAG variants. The aim of this study was to clarify the age- and gender-related differences in carbohydrate concentrations and in drug-binding capacities of AAG glycoforms.


METHODS
The sera used in this study were obtained from 32 healthy subjects (17 men and 15 women, aged 16-84 years). The AAG glycoforms were isolated by hydroxyapatite chromatography. The binding capacity of AAG to disopyramide (DP), which is a basic drug, was determined using the ultrafiltration method. The concentrations of N-acetylneuraminic acid (NeuAc) and monosaccharides in AAG were determined using high-pH anion-exchange chromatography with pulsed-amperometric detection.


RESULTS
The mean plasma AAG concentration in the female subjects was significantly lower than that in the male subjects (0.67 +/- 0.12 mg/ml, mean +/- SD, in females, n = 15, versus 0.81 +/- 0.17 mg/ml in males, n = 17, P < 0.05), but no age-related differences were found (0.75 +/- 0.18 mg/ml in young subjects, n = 24, versus 0.77 +/- 0.12 mg/ml in older subjects, n = 8, n.s.). However, the degree of branching of the glycan chain in the female subjects was significantly lower than that in the male subjects (1.61 +/- 0.17 mol/mol, mean +/- SD, in females, n = 15, versus 1.75 +/- 0.23 mol/mol in males, n = 17, P < 0.05). There was a significant inverse relationship between the binding capacity of AAG to DP (Cb/AAG) and the degree of branching of the glycan chain. The binding capacity (Cb/AAG) decreased as the degree of branching in AAG glycans increased. The binding capacity (Cb/AAG) in the female subjects was significantly higher than that in the male subjects (2.79 +/- 0.59 mg/g AAG in females, mean +/- SD, n = 15, versus 2.37 +/- 0.29 mg/g AAG in males, n = 17, P < 0.05). CONCLUSION. The degree of branching of the glycan chain in AAG plays an important role in drug-binding capacity. Gender-related differences in drug-binding capacity (Cb/AAG) may be caused by differences in the ratios of the extent of branching of the glycan chain in AAG.
Kishino
Satoshi
S
Department of Pharmacy, Hokkaido University Hospital, School of Medicine, Hokkaido University, Sapporo, Japan.
Nomura
Akikazu
A
Itoh
Shin
S
Nakagawa
Tsutomu
T
Takekuma
Yoh
Y
Sugawara
Mitsuru
M
Furukawa
Hiroyuki
H
Todo
Satoru
S
Miyazaki
Katsumi
K
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000889:Anti-Arrhythmia Agents / Q000097:blood; D002241:Carbohydrates / Q000032:analysis*; D004206:Disopyramide / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009961:Orosomucoid / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms; D012737:Sex Factors
D000889:Anti-Arrhythmia Agents; D002241:Carbohydrates; D009961:Orosomucoid; D020033:Protein Isoforms; D004206:Disopyramide