Diamine uptake by rat lung type II cells in vitro

Lung epithelial type II cells are responsible for synthesising and secreting pulmonary surfactant which reduces surface tension and prevents lung collapse. Type II cells replace type I cells and can proliferate in response to alveolar injury. An important aspect of this proliferation may be the abil...

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Published inBiochemical pharmacology Vol. 41; no. 8; p. 1209
Main Authors Oreffo, V I, John, R A, Richards, R J
Format Journal Article
LanguageEnglish
Published England 15.04.1991
Subjects
Animals
Biological Transport - drug effects
Cells, Cultured
Diamines - metabolism
In Vitro Techniques
Iodoacetates - pharmacology
Iodoacetic Acid
Kinetics
Lung - cytology
Lung - metabolism
Ouabain - pharmacology
Paraquat - pharmacology
Potassium Cyanide - pharmacology
Putrescine - metabolism
Rats
Rotenone - pharmacology
Temperature
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Summary:Lung epithelial type II cells are responsible for synthesising and secreting pulmonary surfactant which reduces surface tension and prevents lung collapse. Type II cells replace type I cells and can proliferate in response to alveolar injury. An important aspect of this proliferation may be the ability of type II cells to accumulate amines actively, particularly the endogenous diamine putrescine. Putrescine is accumulated into isolated alveolar type II cells by an energy-dependent process. The uptake obeys saturation kinetics for which an apparent Km of 14.7 microM and Vmax of 130 pmol/micrograms DNA/hr was derived. The inhibitory effects of structurally similar amines on putrescine accumulation are described. As the herbicide paraquat has been suggested to share the same uptake system as putrescine from lung slice studies, this phenomenon was investigated in type II cell cultures. The results demonstrated that paraquat is a partially competitive inhibitor of putrescine accumulation in the cells. The Ki for the inhibition of putrescine uptake by paraquat in type II cells was calculated to be 69 microM, a value which closely matches the Km for paraquat (70 microM) predicted from lung slice studies. In molecular terms, the partial nature of the competition indicates that paraquat and putrescine do not occupy identical sites. Saturation of its site by paraquat reduced the affinity of putrescine 3.6-fold, but did not abolish it.
ISSN:0006-2952
DOI:10.1016/0006-2952(91)90660-W