Age-related fall of the motor function, reproductive function, psychomotor function and respiratory function of the lung are well known. However age-related changes of the metabolic function of the lung are not elucidated yet.
We tried to elucidate the effect of aging on responsiveness of tracheal strips, on activation and inactivation (or uptake) of various vasoactive substances through isolated perfused lung and on change of plasma levels of thromboxane B2 and 6-keto PGF1α in male Wistar rats.
1) The body weight and wet lung weight showed a rapid increase from 1 to 8 weeks, and thereafter the former showed a gradual increase, while the latter reached a plateau.
2) The ED50 of acetylcholine in rat tracheal strips showed a rapid increase from 1 to 12 weeks, and thereafter it showed a gradual increase.
3) Percent inactivation of serotonin through an isolated perfused rat lung showed an age-related increase reaching a plateau from 7 to 36 weeks. Thereafter it showed an age-related decrease.
4) Percent inactivation of prostaglandin E2 through an isolated perfused rat lung showed an age-related increase, reaching a plateau from 7 to 36 weeks. Thereafter it showed an age-related decrease.
5) Percent inactivation of prostaglandin F2α through an isolated perfused rat lung showed an age-related increase reaching a plateau from 7 to 24 weeks and showing a maximum value at 36 weeks, followed by an age-related decrease.
6) Percent activation of angiotensin I through an isolated perfused rat lung showed a maximum value at 1 week. Thereafter it showed an age-related decrease and became stationary from 3 to 24 weeks, following which it again showed an age-related increase.
7) Plasma levels of 6-keto PGF1α and thromboxane B2 did not show any age-related change.
The above results suggest that the percent inactivation of serotonin, prostaglandin E2 and prostaglandin F2α and the percent activation of angiotensin I may show age-related changes.
