Effect of Leukotriene C4 on Glandular Kallikrein Activity in Bronchial Wash of Guinea Pig

Jin, Hong Yong

Abstract

The involvement of plasma kallikrein-kinin system in some pathological states such as bronchial asthma and coughing induced by captopril has been suggested, LTC, and LTD, have been well reported to have a potent activity of bronchoconstriction and mucous secretion. The author tried to confirm whether leukotrienes increase glandular kallikrein activity in bronchial wash or not, and if it is true, to investigate the possible mechanism of leukotrienes-induced increase of glandular kallikrein activity. Bronchial wash was collected from excised lungs of guinea pig, and incubated with synthetic substrate (Pro-Phe-Arg-MCA), and released amount of AMC was measured by fluorescence spectrophotometer as the amidase activity (glandular kallikrein activity). In order to confirm that glandular kallikrein can release kinin, bronchial wash was also incubated with purified LMW- kininogen in the presence of kininase inhibitor (o-phenanthroline), and the amount of kinin was measured by enzyme immunoassay as the kinin releasing activity of glandular kallikrein. The results were as follows: 1) The glandular kallikrein activity (control: 2.98 x 10(-11) mole/min/ml wash) was increased by pilocarpine (12-120 umole/kg, i.v.), and the increased glandular kallikrein activity by pilocarpine (41 nmole/kg, i.v.) was inhibited by atropine (4-43 nmole/kg, i.v.). 2) LTC(4) (1-10 nmole/kg, i.v.) or LTD(4) (1-10 nmole/kg, i.v.) increased the glandular kallikrein activity, but the potency of LTD, was about 1/3 of that of LTC,. The increased glandular kallikrein activity by LTC, (3 nmole/kg, i.v.) was inhibited by ONO-1078 (20-203 nmole/kg, i.p.). 3) The increased glandular kallikrein activity by LTC, (3nmole/kg, i.v.) was inhibited by in- domethacin (8-83 nmole/kg, i.p.), OKY-046 (11-113 nmole/kg, i.v.), atropine (4-43 nmole/kg, i.v.), scopolamine (9-88 umole/kg, i.v.) and Thi-D-Phe-BK (100-1000 nmole/kg, i.v.). 4) STA, (6-60pmole/kg, i.v.) increased the glandular kallikrein activity, and the increased glandular kallikrein activity by STA, (20 pmole/kg, i.v.) was inhibited by atropine (14 umole/kg, i.v.) (p < 0. 001). 5) The increased glandular kallikrein activity by pilocarpine (41 urnole/kg, i.v.) was not inhibited by indomethacin (83 umole/kg, i.p.), but it was inhibited by Thi-D-Phe-BK (300 nmole/kg, i.v.) (p< 0. 001). 6) Bradykinin (3-30 nmole/kg, i.v.) increased the glandular kallikrein activity, and the increased glandular kallikrein activity by bradykinin (30 nmole/kg, i.v.) was inhibited by indomethacin (83 umole/kg, i.p.) or atropine (14 umole/kg, i.v.) (p<0.001). 7) The kinin releasing activity by glandular kallikrein in bronchial wash was 24 x 10 " mole/min/ ml wash in control group, and it was markedly increased in pilocarpine-pretreated group (124 x 10 mole/min/ml wash) (p<0.05), and in LTC4-pretreated group (164x10 mole/min/ml wash) (p<0. 01). The increased kinin releasing activity by LTC, (3 nmole/kg, i.v.) was completely inhibited by aprotinin (5000IU/ml, i.v.). I could conclude that i ) LTC, and LTD, increased glandular kallikrein activity in bronchial wash of guinea pig, ii) the most possible mechanism of LTC,-induced increase of glandular kallikrein activity in bronchial wash may be as follows; LTC,TXA,aeetyleholineinerease of glandular kallikrein acitivity, and iii) kinin released by glandular kallikrein may enhance the action of TXA, or acetylcholine to increase the glandular kallikrein activity.