Platelet monoamine oxidase-A activity and aging: effect of carnosine

Abstract

Platelet mitochondrial MAO-A activity of male albino rats (Wistar strain) was significantly inhibited with an inhibition of its only V max during aging. This age-induced inhibition of platelet MAO-A activity became reversed following the application of higher dosages (2.0-2.5 μg/kg/day, i.t. for 21 consecutive days) of carnosine. Though carnosine at lower dosage (0.5 μg/kg/day, i.t. for 21 consecutive days) was ineffective to platelet mitochondrial MAO-A activity in both young and aged rats, at higher dosages (2.0-2.5 μg/kg/day, i.t. for 21 consecutive days) under similar condition this enzyme activity was significantly enhanced. Carnosine at 1.0 μg/kg/day, i.t. for 21 consecutive days significantly enhanced MAO-A activity only in aged (18 and 24 months) rats. These results suggest that carnosine withdraws the aging-induced inhibition of mammalian blood platelet MAO-A activity and restores its activity towards that (MAO-A activity) observed in young mammalian blood platelets.

Fig. 1

Effect of carnosine on rat blood platelet MAO-A activity during aging of male rats. Results are expressed as mean ± SEM (n = 4–6). Each observation was made from a single rat. Change (%) was calculated with respect to the corresponding age-matched control group of rats (4, 18 and 24 months). a Significantly different from corresponding control were: (i) young (4 months) rats ^a p < 0.001, (ii) aged (18 months) rats ^b p < 0.001, (iii) aged (24 months) rats ^c p < 0.001. b Significantly different from corresponding carnosine treated (dose/day for 21 consecutive days, i.t.) were: young (4 months) rats (i) 0.5 μg/kg ^d p < 0.001, (ii) 1.0 μg/kg ^e p < 0.001, (iii) 2.0 μg/kg ^f p < 0.001, (iv) 2.5 μg/kg ^g p < 0.001

Fig. 2

a Effect of serotonin concentration variation (0.05–0.4 mM) on platelet MAO-A activity. Results are expressed as mean ± SEM (n = 4–6). Each observation was made from a single rat. Line (–) represents control, filled circle young (4 months) rats, filled square aged (18 months) rats, filled triangle aged (24 months) rats. Broken line (---) indicates carnosine treated, open circle young (4 months) rats, open square aged (18 months) rats, open triangle aged (24 months) rats. b Line–Weaver Burk plot of blood platelet MAO-A activity in different ages of rats. Line–Weaver Burk plots were drawn from the progress curve with varying substrate concentration as presented in a