A sensitive, modified
3,5-diaminobenzoic acid (
DABA), fluorometric
DNA assay was developed and compared to
mithramycin and
ethidium bromide assays in determining the
DNA content of dense connective tissues including: Swarm rat
chondrosarcoma, rabbit, dog, monkey, and most importantly, adult human articular cartilage. In the more cellular cartilages, the three methods gave equivalent results. However, in the relatively acellular human cartilage, the
DABA method was shown to be superior. Both the
mithramycin and
ethidium bromide gave falsely high values compared to the
DABA method, which by subtraction after
DNase digestion approached the
DABA value. The latter was completely
DNase sensitive. With the
DABA method, the
DNA content of human cartilage can be obtained on less than 5 mg wet weight of fresh, alcohol-fixed, or lyophilized material. While the
DNA can also be released by digestion with
papain or
protease from Streptomyces griseus,
proteinase K was preferable. The comparison of literature values for other fluorometric and spectrophotometric assays of human cartilage suggest these methods overestimate human articular cartilage
DNA concentrations, whereas the
DABA values were in line with those predicted from previous morphometric analysis. Thus, the modified method represents an improvement in
DNA analysis of dense connective tissues.