Quantitation of intraplatelet Ca++ deposits as a potential marker of senility.
OBJECTIVE
To perform a morphometric evaluation of calcium deposits in human platelets as a quantitative procedure to seek a potential marker of senility in a peripheral cellular model.


METHODS
In human blood samples from middle-aged, healthy volunteers, the intraplatelet calcium content was cytochemically evidenced by the oxalatepyroantimonate (OPA) reaction. The number and area of OPA aggregates per square micrometer of total sampled area, the area of the deposits per square micrometer of platelet surface and the percentage of positive platelets were the ultrastructural features calculated by computer-assisted image analysis.


RESULTS
OPA precipitates were easily identified in all the samples evaluated. The area of OPA deposits per square micrometer of platelet surface was rather constant not only among the measurements performed on the same sample but also comparing the different subjects analyzed. Other OPA deposit features showed higher variabilities; thus, to obtain a representative sample from each patient, several measurements had to be carried out.


CONCLUSIONS
Quantitation of calcium deposits may be of help in evidencing increased Ca++ sequestering activity by platelets, supposedly due to altered calcium homeostasis. The OPA cytochemical procedure visualizes millimolar quantities of Ca++ ions; thus, only high calcium concentration sites (granules) can be detected by morphometric methods.
Bertoni-Freddari
C
C
N. Masera Research Department, Italian National Research Centers on Aging, Ancona, Italy.
Galeazzi
L
L
Casoli
T
T
Fattoretti
P
P
Caselli
U
U
Paoloni
R
R
D000375:Aging / Q000097:blood*; D000544:Alzheimer Disease / Q000097:blood / Q000503:physiopathology; D000965:Antimony / Q000378:metabolism; D015415:Biomarkers / Q000097:blood; D001792:Blood Platelets / Q000737:chemistry* / Q000648:ultrastructure; D002118:Calcium / Q000097:blood*; D011232:Chemical Precipitation; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry; D008854:Microscopy, Electron; D008875:Middle Aged; D010070:Oxalates / Q000378:metabolism
D015415:Biomarkers; D010070:Oxalates; C009133:pyroantimonate; D000965:Antimony; D002118:Calcium