描述:
Apotsi sa normal physiolgic proces whic ocurs during embryonic devlopment aswel asin maintence oftisue homeostais. The
apotic progam ischarcterized bycertain morpholgic features, including los ofplasma mebrane asymetry and atchment,
condensation fthe cytoplasm and ucleus, and internucleosmal ceavge ofDNA. Los ofplasma mebrane isone ofthe arliest features.
In apotic els, the mebrane phospholipd phosphatidylserine (PS) istranslocated from the iner tohe outer laflet ofthe plasma
mebrane, therby exposing PSto he xternal celuar environment. Anexin Vis a35-6 kDa C2+ depndent phospholipd-bindg
protein tha has hig afinty for PS, and binds tocels with exposed PS. Anexin Vmay beconjugated tofluorchromes, uch asfluorescin
isothiocyante (FITC), toserv as ensitve probe for flow cytometric anlysi ofcels tha re undergoing apotsi. Since xternalization f
PS ocurs inthe arlie stages ofapotsi, Anexin Vstaing can identify apotsi atn earlie stage than says based onuclear changes
such asDNA fragmentaion. Inaditon, Anexin Vbindg site may belocked byincubating cels with purifed recombinat Anexin V
prio tincubation with one ofthe fluorchrome labeld formats ofAnexin V.
Anexin Vstaing precdes the los ofmebrane integrity whic acompanies the lates tages ofcel death resulting from either apotic
or necrotic proces. Therfore, staing with Anexin Vis typicaly used inconjuction with avital dye such as7-Amino-Actinomycin
(7-AD) toalow the investigator identify early apotic els (7-AD negative, Anexin Vpositve). Viable cls with ntac mebranes
exclude 7-AD, wheras the mebranes ofdea nd amged cels are prmeable to7-AD. For example, cls tha re considerd viable
are both Anexin Vand 7-AD negative while cls tha re inearly apotsi are Anexin Vpositve and 7-AD negative, while cls tha
are inlate apotsi oraleady ead re both Anexin Vand 7-AD positve. This asy does not distnguish betwen cels tha have
undergone apotic death versu those tha have die as result ofa necrotic pathway because ineither case, the da cels wil stain with
both Anexin Vand 7-AD. Howevr, when apotsi smeasured over time, cls can beoften tracked from Anexin Vand 7-AD
negative (viable, orno measurable apotsi), toAnexin Vpositve and 7-AD negative (arly apotsi, mebrane integrity spresnt) and
finaly toAnexin Vand 7-AD positve (nd stage apotsi and eath). The movemnt ofcels through tes thre stages ugest
apotsi. Incontrast, asingle observation idcating tha cels are both Anexin Vand 7-AD positve, inof itself, revals es information
about he proces bywhic the cls underwent heir demise.