| As the major effective component of licorice root, & -Glycyrrhizin (18 β - Glycyrrhizic acid, β -GA) has antiinflammatory, antivirusand anti-allergic effects . Through isomerization, it can turn into a -Glycyrrhizin( a -GA), which exhibites a more potential anti-inflammatory effect in hepatitis disease. Due to the inhibitory effects on 11β-hydroxysteroid dehydrogenase (11β-OHSD2), β-GA has many adverse reactions in clinical therapy, such as hypertension, hypokalemia etc. In case of a -GA , similar mild adverse reactions are also reported, however, the related mechanism remaines unknown. The aim of present study is to determinate whether a -GA inhibits the activity of 11β-OHSD2 and reveal the coleration between inhibition of IIβ -OHSD2 and the adverse reactions observed in a -GA treatment. Through experiments both in vivo and in vitro,ve examined either the effects of α-GA on of 11β-OHSD2 or the adverse reactions caused by α-GA treatment, so as to provide evidence for optimized administration in clinical therapy.1. Inhibitory effects of α-GA on 11β-OHSD2 in vitro.Microsomal 11β -OHSD2 was prepared from the honogenate of multicoloured Hartley guinea pig kidney cortex and its activity was determinated from the conversion percentage of cortisol to cortisone . Inhibitory effects of α-GA on 11β-OHSD2 activity in vitro were studied. Results: (1) the conversion percentage of cortisol tocortisone in control with homogenate preparation was 99%. When the concentrations of a. p-GA were below 0.8 mmol/L, the conversion of cortisol percentage was more than 96%. When the concentrations were 1. 6 mmol/L, the conversion percentages of cortisol in a -GA group and P -GA group were 98.55% and 90.51% respectively. When the concentrations were up to 3.2 mmol/L, the percentages of a-GA group and 3-GA group were 62.59% and 38.64% respectively. The inhibitory effects of a-GA on 11P-OHSD2 activity showed dose- dependent. (2) When the concentrations were 0.8,0.4,0.2 mmol/L, the conversion percent rates of cortisol by microsomal IIP -OHSD2 in a -GA group and P-GA group were 38. 99?. 85, 21. 08?. 5(n=3) ; 53. 37?. 63, 33. 09?0. 19(n=3); 60. 41+0. 86, 44. 67 ?. 33 (n=3) respectively. Compared with the conversion percentages of cortisol in control(70.56 + 3.03, n=3), the reduction of the percentage was significant (/<0. 05). The ICsoS were 1140. 1 and 346.4 nmol/L for a-GA and P-GA respectively. This suggested that the inhibitory effects of a-GA on 11P-OHSD2 from Hartley guinea pig kidney were less potent than 3 -GA. (3) Using three batches kidney microsomal 11P-OHSD2, of which every batch was experimented thrice, the average conversion percentage of cortisol in control, a-GA group and 3 -GA group were 70. 56%?3.03%, 38. 99%?. 85%, 21.08%+1. 50%: 70. 93%+4.62%, 38.2%+2.28%> 21. 55% + 1. 38% ; 71. 80% + 2. 33% , 38. 80% + 1. 98% , 21. 50% ?.61% respectively. Using t test, the reciprocal average conversion rates of cortisol in three batches microsomes were compared each other and showed no significant difference(/^0. 05). In one batch microsomes, the conversion rates of cortisol in varying group were compared and showed significant difference(/<0.05). This suggested that a -GA could inhibit the activity of 11P-OHSD2 in vitro, but was less potent than P-GA.2. Determination of kinetic constants of microsomal 110-OHSD2Using 4 concentrations of cortisol,5 different concentrations of a -GA were added into kidney cortex microsomal suspension and yielding velocity of cortisone was determinated. Kinetic constants of microsomal IIP -OHSD2 were calculated from the double reciprocal plots according to Michaelis-Menten equation and Dixon equation. Results: The effects of inhibition by a -GA at varying concentrations of cortisol on the 113 -OHSD2 were shown as a double reciprocal plot. Most of the lines converged on the ordinate, which indicated that the inhibition by a -GA was competitive. H,=15. 25 nmol. mg"1. h"land 10=1. 31 y mol/L were calculated. According to Dixon plot, ?209.2 u mol/L ?7. 1 u mol/L was calculated.3...
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