Detection of nitric oxide synthase isoenzymes (NOS) in normal and alterated synovial membrane from equine metacarpophalangeal joint

Abstract

We studied the presence of NOS isoforms in synovial membrane from equine metacarpophalangeal joint. This was considered a normal joint group NN (n = 13) when there was not any visual damage of joint structures. The damaged groups were classified as follows: NA (n = 8) with congestive synovial membrane without cartilage damage; AN (n = 10) cartilage damage and normal synovial membrane and AA (n = 8) those with cartilage damage and congestive synovial membrane. Damaged cartilage showed erosions and multiple wear lines. Detection of NOS isoforms was performed by western blot using monoclonal antibodies. The generated chemiluminescence was measured and expressed in densitometric relative units (DRU) that represent the rate between the pixels of each sample and those of the standard. NOS I showed a 145 kDa band in all samples, without significant differences between joint groups. NOS III showed a 140 kDa band, with detection percentages of NN = 77%; NA = 63%; AN = 30% and AA = 100%, without significant differences between them. NOS II was no detected in these samples. In conclusion, NOS I and partially NOS III, were expressed in a constitutive form in equine synovial membrane, while NOS II was not detected in these assays, which was likely to be expected given the absence of acute inflammation, at least during macroscopic observation.