Effect of thyrotropin on phospholipid composition in thyroid plasma membranes.

Differences particular in phospholipid levels from pig thyroid membranes incubated in the presence of TSH were observed, but with exception of lysophosphatidylcholine, were not statistically significant. TSH evoked about a twice increase of lysophosphatidylcholine content. A slight decrease of phosphatidylcholine, phosphatidylinositol and phosphatidylserine were found, when at the same time a slight increase of phosphatidylethanolamine and sphingomyelin level was noted. There were no statistical differences in range fluctuation of individual phospholipid levels, but direction of fluctuation (i.e. decrease or increase) were identical for every single phospholipid in all experiments. An increase of lysophosphatidylcholine and a simultaneously decrease of phosphatidylcholine contents suggests the stimulation of phospholipase A2 activity.