Effect of insulin on aminoisobutyric acid uptake by human non-rheumatoid and rheumatoid synovial cells.

The biological sensitivity of cultured non-rheumatoid human synovial cells (NRSCs) and rheumatoid synovial cells (RSCs) was examined in terms of the ability of insulin to stimulate the uptake of alpha-aminoisobutyrate (AIB). NRSCs, like numerous fibroblastic lines, were sensitive to physiological concentrations of the hormone: half-maximal stimulation was obtained with (4 X 10(-10) M) insulin, while maximum transport was found with a 60-90 min association time. On the contrary, although the basal transport was similar in RSCs, insulin was totally unable to accelerate AIB transport in these cells. Inflammatory processes lead to an insulin resistance which most likely involves a post-receptor step at the cellular level.