Differential regulation of nitric oxide synthase-II mRNA by growth factorsin rat, bovine, and human retinal pigmented epithelial cells

Retinal pigmented epithelial cells (RPE cells) express the inducible isofor m of NO synthase (NOS-II) after stimulation by cytokines and endotoxin. We have attempted to describe and compare the effect of fibroblast growth fact or (FGF) and transforming growth factor beta (TCF beta) on NOS-II mRNA leve l in three different cell species:rat, bovine, and human. Northern blot ana lysis demonstrated that, in the rat RPE cells, FCF upregulates and TGF beta inhibits NOS-II mRNA accumulation, whereas in the bovine cells, the opposi te effect appears. For the human RPE cells, RT-PCR analysis demonstrated th at FGF upregulates and TGF beta inhibits NOS-II mRNA accumulation, as in ra t cells, even though the effect of TGF beta was weaker. Thus, this study de monstrates that marked differences in growth factors regulating NOS-II occu r between species, suggesting fundamental signal transduction differences a t some level between rat, human, and cow.