Related Experiment Videos
Heat-stable alkaline phosphatase as a marker for human and monkey type-I pneumocytes
E J Nouwen1, N Buyssens, M E De Broe
1Department of Nephrology and Hypertension, University Hospital Antwerpen, Edegem, Belgium.
Insights
Heat-stable alkaline phosphatase is found in human and monkey lung type-I pneumocytes. This enzyme
Area of Science:
- Cell Biology
- Histology
Background:
- Alkaline phosphatase (AP) is an enzyme with various isoenzymes.
- The heat-stable isoenzyme of AP has implications in cellular function and disease states.
Purpose of the Study:
- To investigate the expression and localization of heat-stable alkaline phosphatase (HSAP) in human and non-human primate lungs.
- To compare HSAP expression levels between human and monkey lungs.
Main Methods:
- Light and electron microscopy.
- Cytochemical and immunocytochemical techniques using antibodies against human term-placental alkaline phosphatase.
Main Results:
- HSAP was detected in type-I pneumocytes in both human and monkey lungs.
- In monkeys, all type-I cells expressed HSAP, while in humans, expression was observed in a subset of type-I cells and some respiratory bronchiolar cells.
- Human lung HSAP expression was 10-fold lower than in monkeys; expression began in human fetal lungs around 17-20 weeks gestation.
Conclusions:
- Heat-stable alkaline phosphatase is a specific marker for type-I pneumocytes in humans and monkeys.
- The subcellular localization of HSAP may contribute to its rapid release into circulation under specific physiological or pathological conditions.
Abstract:
The expression of the heat-stable isoenzyme of alkaline phosphatase in the human and monkey (Macaca mulatta, M. fascicularis) lung was investigated at the light- and electron-microscopic level, using cytochemical techniques and immunocytochemical procedures based on monoclonal and polyclonal antibodies against human term-placental alkaline phosphatase. Both in man and monkey, the enzyme was present in type-I pneumocytes. In the monkey, the enzyme was found in all type-I cells. In man, strong staining was observed only in some type-I cells and in certain cuboidal respiratory bronchiolar cells. Staining was localized on the apical and basal plasma membrane, in apical and basal caveolae, and in the underlying basement membrane. The level of heat-stable alkaline phosphatase expression in the human lung was 10-fold lower than in the monkeys studied. In human fetal lung, the onset of heat-stable alkaline phosphatase expression was associated with the development of the alveolar epithelium from 17-20 weeks gestation onward. It is concluded that: (1) heat-stable alkaline phosphatase is a specific constituent of type-I pneumocytes in man and monkeys; and (2) its subcellular localization may explain its rapid appearance in the circulation under certain conditions.