Am. J. Respir. Crit. Care Med., Vol 151, No. 5, 05 1995, 1621-1624.
The effect of inhalation of platelet-activating factor on the pulmonary clearance of 99mTc-DTPA aerosol
GR Mason, AM Peters, MJ Myers, PW Ind and JM Hughes
Department of Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom.
Platelet-activating factor (PAF) is a short-acting, lipid-soluble autocoid,
inhalation of which causes an immediate pulmonary vascular sequestration of
granulocytes and a peripheral neutropenia. We investigated the effect of
PAF inhalation on the pulmonary clearance rate of inhaled 99mTc-DTPA in
order to test the hypothesis that the pulmonary sequestration of
granulocytes results in acute lung injury. In nine normal nonsmoking
adults, the rate of clearance of DTPA, corrected for background activity,
was 1.5 (SD 0.7) %/min over the first 10 min after inhalation. Inhalation
of 4.8 micrograms PAF abruptly increased the clearance rate to a mean value
of 2.3 (1.4) %/min (p < 0.05). No increase in clearance was observed in
four nonsmoking subjects who inhaled vehicle only. The mean overall
increase after PAF was 87% of the baseline clearance, significantly
different (p < 0.05) from the corresponding change in the control group,
which was - 17%. After PAF, the clearance rate returned to baseline values
within 10 min in all subjects. In all subjects who inhaled PAF, but in none
who inhaled vehicle, there was an immediate neutropenia of 51 (SD 25) % of
the baseline value (p < 0.01). This neutropenia persisted longer than
the corresponding accelerated DTPA clearance and was still 74 (36) % of the
baseline value at 10 min. Furthermore, there was no correlation between the
increase in DTPA clearance induced by PAF inhalation and the decrease in
peripheral blood granulocyte count. We conclude that PAF inhalation results
in an increase in pulmonary DTPA clearance, probably not mediated by
pulmonary vascular granulocyte sequestration.
