Am. J. Respir. Crit. Care Med., Vol 149, No. 5, May 1994, 1180-1185.
Viral respiratory infection causes airway hyperresponsiveness and decreases histamine N-methyltransferase activity in guinea pigs
H Nakazawa, K Sekizawa, M Morikawa, K Yamauchi, M Satoh, K Maeyama, T Watanabe and H Sasaki
Department of Geriatric Medicine, Tohoku University School of Medicine, Sendai, Japan.
We investigated the effects of viral respiratory infection by Sendai virus
on bronchial responses to aerosolized histamine in anesthetized guinea pigs
and on the activity of histamine N-methyltransferase (HMT). We measured the
change in total pulmonary resistance induced by histamine in the presence
or absence of a specific HMT inhibitor, SKF 91488, in noninfected and
infected animals. In the absence of SKF 91488, the bronchoconstrictor
response to histamine was greater in infected than in noninfected animals.
SKF 91488 (10(-2) M, 90 breaths) potentiated the responses to histamine in
noninfected animals, and the magnitude of augmented responses to histamine
by SKF 91488 was similar to that by viral infection. Furthermore, SKF 91488
did not further potentiate the responses to histamine in infected animals.
However, responses to aerosolized acetylcholine were unaffected by viral
infection and SKF 91488. The HMT activity decreased by 56% in the trachea,
86% in the bronchi, and 52% in the parenchymal tissue in the infected
animals. In contrast to HMT activity, acetylcholinesterase activity was
unaffected by viral infection. These results suggest that respiratory
infection by Sendai virus causes enhanced bronchial responsiveness to
histamine by decreasing HMT activity in airways.
