Uptake and disposition of putrescine, spermidine, and spermine by rabbit lungs

The pulmonary uptake and accumulation of the three polyamines in intact, ventilated, and perfused rabbit lungs was investigated. Lungs were perfused using Krebs-Ringer bicarbonate buffer with albumin in which putrescine, spermidine, or spermine were included at an initial concentration of 10(-3), 10(-2), 10(-1), 5, 10, or 20 mM. At a 5 mM concentration of spermidine and spermine, the uptake by isolated lungs reached a steady state equilibrium in 20-30 min of perfusion. This did not occur for putrescine, which showed linear uptake throughout the entire period of the 60-min perfusion. The lung uptake of putrescine for all perfusate concentrations was greater than that of spermidine or spermine, but all three showed concentration-dependent linear uptake. In the presence of harmaline (1 mM) and ouabain (1 mM), isolated perfused rabbit lungs showed a decrease in uptake of putrescine although no effect was seen for spermidine and spermine. Perfusate containing decreased sodium showed no effect on putrescine uptake by isolated rabbit lungs, but there was a significant increase in the uptake of spermidine and spermine. Significant uptake of all three polyamines was also observed when incubated separately with rabbit lung slices for 60 min. HPLC analysis of lung, the perfusate samples, lung slices, and the incubation medium after a 60-min incubation did not indicate the presence of metabolites of these polyamines. Likewise, the analysis of the lung homogenate incubated with polyamines did not show any metabolites confirming the absence of detectable pulmonary metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)