AJP - Lung Cellular and Molecular Physiology, Vol 269, Issue 1 71-L77, Copyright © 1995 by American Physiological Society
Characterization of zinc uptake and its regulation by arachidonic acid in fetal type II pneumocytes
T. J. Ong, P. J. Kemp, R. E. Oliver and H. J. McArdle
University of Dundee, Department of Child Health, Ninewells Hospital and Medical School, United Kingdom.
In freshly isolated fetal guinea pig type II pneumocytes, zinc uptake is
time and temperature dependent. Two pathways of uptake exist, resulting in
a rapid phase that reaches a steady state within 30 s and a slower linear
phase that does not attain a steady state within 60 min. Both processes
exhibit saturation kinetics. The rapid phase has a maximal zinc uptake of
60.7 +/- 9.3 pmol.10(6) cells-1.30 s-1 and an apparent affinity (Kt) of
13.7 +/- 5.4 microM. The maximum velocity of uptake (Vmax) of the slower
phase is 24.6 +/- 1.9 pmol.10(6) cells-1.min-1 with a Kt of 22.0 +/- 3.6
microM. Epinephrine, terbutaline, dibutyryl adenosine 3',5'-cyclic
monophosphate, and dexamethasone have no significant effect on zinc uptake,
while arachidonic acid (AA) stimulates. Dose-response data of AA-stimulated
zinc uptake gives an apparent K0.5 of 0.42 +/- 0.01 microM and a Hill
coefficient of 1. The maximal uptake in the rapid phase is significantly
increased to 146.8 +/- 12.4 pmol.10(6) cells-1.30 s-1 and in the slow
phase, the Vmax for zinc uptake is also significantly increased to 33.0 +/-
1.8 pmol.10(6) cells-1.min-1 by 10 microM AA. However, the Kt values in
both processes remain unchanged after AA stimulation. The effect is not
mediated by either leukotrienes or prostaglandins but can be mimicked by
other unsaturated fatty acids.
