The influence of age on isolated tracheal responsiveness to spasmogens

The extract from Nandina domestica THUNBERG inhibits histamine- and serotonin-induced contraction in isolated guinea pig trachea

Although the fruit of Nandina domestica THUNBERG (ND) has been used to treat respiratory disorders such as coughing and breathing difficulty in Japan for many years, very little is known about mechanisms underlying its action. In the present study, we investigated effects of the crude extract from ND (NDE) and one of its constituents, nantenine, on contractile responses in isolated guinea pig tracheal ring preparations. In normal experimental condition, guinea pig trachea remained tonically contracted during the resting state, and addition of NDE (1 mg/ml) caused a relaxation of tracheal smooth muscles, but had little effect on the responsiveness of trachea to acetylcholine. The basal, tonic contraction was abolished by the presence of atropine and indomethacin. In this condition, NDE at 0.1-1 mg/ml inhibited histamine-induced contraction in both competitive and non-competitive manners. NDE at 0.01-1 mg/ml inhibited serotonin-induced contraction in a competitive manner. Nantenine (2-20 microM) did not affect histamine-induced contraction, and slightly inhibited serotonin-induced contraction. These results suggest that NDE has inhibitory effects on tracheal smooth muscle contraction, and nantenine cannot account solely for this effect of NDE.

Inhibitory effects of angiotensin-converting enzyme (ACE) inhibitors on oxygen radicals produced by bronchoalveolar lavage cells in young and aged guinea pigs

We examined the effect of angiotensin-converting enzyme (ACE) inhibitors and age on oxygen radical formation by bronchoalveolar lavage (BAL) cells. Lung-free cells, including pulmonary alveolar macrophages, were harvested from young (4-month-old) and aged (28-month-old) male guinea pigs using BAL. The oxygen radicals produced by BAL cells were measured by a lucigenin-dependent chemiluminescence method using a photon counter. Although spontaneous oxygen radical production by BAL cells from young and aged guinea pigs did not differ, the oxygen radical generation after maximal stimulation with phorbol-myristate acetate (PMA) was greater than that produced without PMA stimulation in both young and aged animals. ACE inhibitors with and without an SH-group (alacepril and lisinopril, respectively) were tested for their effect on oxygen radical formation by BAL cells; both ACE inhibitors inhibited oxygen radical production and generation by BAL cells from both young and aged guinea pigs in a dose-dependent manner. However, the alacepril concentration giving 50% inhibition (IC50) of oxygen radical generation by BAL cells was smaller than the IC50 of lisinopril in both young and aged guinea pigs. These results indicate that ACE inhibitors, in particular those with an SH-group, effectively reduce oxygen radical production by BAL cells from young and aged guinea pigs, and suggest that treatment with ACE inhibitors may be useful for ameliorating oxidant-associated pulmonary disorders in young and aged patients.

Age-related changes in airway responsiveness to phosphodiesterase inhibitors and activators of adenyl cyclase and guanylyl cyclase

The influence of animal age on the responsiveness of guinea-pig and rat isolated tracheal smooth muscle to the non-selective inhibitors of phosphodiesterase, theophylline and papaverine and to the adenylyl cyclase and soluble guanylyl cyclase activators, forskolin and sodium nitroprusside respectively, was examined. Significant age-related decreases in the potencies of theophylline and papaverine were observed across the age ranges in guinea-pig (2.8- and 3.4-fold decreases respectively) and rat (1.9- and 2.6-fold decreases respectively) trachea, suggesting age-related falls in the activity of phosphodiesterase in these tissues. However, maximum relaxant responses (E(max)) to these agents were not altered with increasing animal age. The relaxant potency of sodium nitroprusside also decreased 4.4-fold across the age range in guinea-pig isolated trachea but not in rat isolated tracheal tissue, suggesting age-related falls in soluble guanylyl cyclase activity in guinea-pig trachea. In contrast, neither forskolin potency nor E(max)changed significantly with increasing age in either guinea-pig or rat tracheal tissue. The present data indicate that ageing in both guinea-pigs and rats was associated with decreased relaxant potency of phosphodiesterase (PDE) inhibitors rather than to changes in adenylyl cyclase activity although reduced soluble guanylyl cyclase activity was also detected in the guinea-pig.

Effect of ambroxol on oxygen radical production and generation by bronchoalveolar lavage cells in young and aged guinea pigs

We examined the effect of ambroxol and age on oxygen radical production and generation with stimulation of phorbol-myristate acetate (PMA) by bronchoalveolar lavage (BAL) cells. Lung free cells including pulmonary alveolar macrophages were harvested from young (4-month-old) and aged (28-month-old) male guinea pigs using BAL. The oxygen radicals produced by BAL cells with or without stimulation of PMA were measured by the lucigenin-dependent chemiluminescence method using a photon counter. Oxygen radical production and generation by BAL cells were not different between young and aged guinea pigs. However, the oxygen radical generation after stimulation with PMA was greater than the oxygen radical spontaneous production both in young and aged animals. Ambroxol solution given into culture media containing BAL cells inhibited oxygen radical production and generation by BAL cells harvested from both young and aged guinea pigs in a concentration-dependent manner. Approximately 16-20 microM of ambroxol inhibited 50% of the production of oxygen radicals in vitro by BAL cells in young and aged guinea pigs, whereas a slightly greater amount of ambroxol was necessary to inhibit 50% of the PMA-induced oxygen radical generation in vitro by BAL cells in guinea pigs. These results indicate that ambroxol inhibits oxygen radicals produced by BAL cells from young and aged guinea pigs, and they suggest that ambroxol may be a possible therapeutic modality for ameliorating oxidant associated pulmonary disorders in young and aged patients.