Putrescine uptake in hamster lung slices and primary cultures of
type ii pneumocytes.
Hoet, Peter H. M., Christian P. L. Lewis, David Dinsdale, Maurits
Demedts, Benoit Nemery, K. U. Leuven.
Laboratorium voor Pneumologie, Herestraat 49, B-3000 Leuven,
Belgium, Tel: + 32-(0)16-34 71 21, Fax: + 32-(0)16-34 71 24
APStracts 2:0115L, 1995.
Putrescine is accumulated into the lungs of various species by an
active uptake system which also mediates the uptake of cystamine and
paraquat. We have characterized this uptake in both lung slices and
type II pneumocytes, isolated from hamsters by trypsin digestion,
differential adherence on plastic and centrifugation on a
discontinuous Percoll gradient. The accumulation of [14C]-putrescine
into lung slices was shown to be temperature and energy dependent,
and to obey saturation kinetics, with mean calculated values of
apparent Km 29.4 [mu]M and Vmax 637 nmol/g/h. In the presence of
cystamine or paraquat, the putrescine uptake was reduced in a manner
compatible with competitive inhibition. The calculated Ki values were
16 [mu]M and 1017-1328 [mu]M for the inhibition by cystamine and
paraquat, respectively. The cellular localisation of tritium-labelled
putrescine in lung slices, following incubation with 2.5 [mu]M
putrescine, was determined by light-microscopical autoradiography.
Labelling was present in type II and possibly also in type I
pneumocytes of the alveolar epithelium, but not in macrophages, in
the endothelium or in cells of the interstitium. Two days after their
isolation, cultured type II pneumocytes exhibited an uptake of
putrescine which had similar kinetic characteristics as in slices (Km
of 23 [mu]M and Vmax of 3.06 [mu]mol/g protein/h) and which was also
competitively inhibited by paraquat (Ki of 222-350 [mu]M paraquat).
Our data demonstrate the presence of an active uptake system for
putrescine in both lung slices and in cultured type II pneumocytes.
This alveolar epithelium-specific polyamine uptake system may
represent a useful biochemical parameter of cell dysfunction in
primary cultures of type II pneumocytes.
Received 24 February 1995; accepted in final form 28 June 1995.
APS Manuscript Number L58-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.