A cytochemical study of glucose-6-phosphatase (G-6-Pase) was made to s
ee the changes in mucopolysaccharide metabolism in the synovial membra
ne during osteoarthritis, because the tissue is thought to play an imp
ortant role in synovial fluid production by providing lubrication to t
he wear-and-tear surface of the synovial cartilage in osteoarthritis,
In normal and osteoarthritic synovial membranes, a high G-6-Pase activ
ity was clearly demonstrated in the cisternal spaces of the rough endo
plasmic reticula, especially in the B cells of the thickened synovial
membrane. The existence of an AB cells intermediate in character betwe
en A and B, was noted in having a high G-6-Pase activity in the accumu
lated rough endoplasmic reticula in the cytoplasm as B cells do locate
d at the deeper part of the membrane, but also whose cell surface exte
nds to the top of the membrane surface reaching into the synovial cavi
ty, and protrude microvilli of a ruffled border indicating a high phag
ocytotic activity as A cells do. The existence of the AB cell is clear
ly one of intermediate structure and function, contributive to the com
pensatory and regenerative action of the synovial membrane.