Characterization of zinc uptake and its regulation by arachidonic acid in fetal type II pneumocytes.
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.
Ong
T J
TJ
University of Dundee, Department of Child Health, Ninewells Hospital and Medical School, United Kingdom.
Kemp
P J
PJ
Oliver
R E
RE
McArdle
H J
HJ
D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005333:Fetus / Q000166:cytology / Q000378:metabolism*; D006168:Guinea Pigs; D011650:Pulmonary Alveoli / Q000196:embryology*; D015032:Zinc / Q000493:pharmacokinetics*
D016718:Arachidonic Acid; D015032:Zinc