Expression of transforming growth factor-β1 and β2 in rat glomeruli

Abstract

The transforming growth factors-β are potent modulators of cell growth and extracellular matrix metabolism in most types of cultured cells. The distribution and functions of TGF-β in vivo are less well known. We utilized several different techniques including northern blots, a CCl-64 cell growth inhibition assay, and sandwich enzyme-linked immunosorbent assays (SELISA) to examine the expression of TGF-β1 and TGF-β2 in rat glomeruli. High levels of TGF-β1 mRNA and protein were found in glomeruli (56 ± 22 ng TGF-β1/g tissue). These levels were several-fold higher than those present in whole kidney (10 ± 5 ng/g). TGF-β2 mRNA was present in glomeruli but was not detected in whole kidney. TGF-β2 concentrations by SELISA were 19 ± 8 ng TGF-β2/g in glomeruli and less than 5 ng/g in whole kidney. Since TGF-β has such marked effects on cell growth, we also examined whether alterations in TGF-β expression were associated with the renal hypertrophy which follows unilateral nephrectomy. Expression of TGF-β1 mRNA decreased in glomeruli following nephrectomy. However, this was not associated with a significant fall in glomerular TGF-β1 protein concentration. Whole kidney levels of TGF-β1 and its mRNA were unchanged following nephrectomy. Similar results were obtained for TGF-β2. Our data document the presence of high concentrations of TGF-β1 and β2 and and their corresponding mRNAs in normal rat glomeruli. These results suggest that TGF-β may play important regulatory roles in the normal glomerulus.