VASOACTIVE AGENTS AFFECT GROWTH AND PROTEIN-SYNTHESIS OF CULTURED RAT MESANGIAL CELLS

Mesangial cell (MC) proliferation and extracellular matrix (ECM) formation are hallmarks of chronic glomerular disease. The present in vitro study examined the effects of the vasoactive agents angiotensin II (Ang II), arginine vasopressin (AVP), and serotonin (5-HT) on growth and protein biosynthesis of cultured rat MCs after 72 hours of incubation. AVP and 5-HT (10(-6 M) significantly increased DNA synthesis and growth of quiescent subconfluent MCs to levels of 25 and 45%, respectively, of the optimal stimulatory effect of 10% fetal calf serum (FCS) (both P < 0.001). The mitogenic effect of Ang II was 10% of the 10% FCS effect (P < 0.01). ECM production was studied by ELISA assay for fibronectin (FN) secreted into the culture medium (SeFN) and cell-associated FN, that is, intra- and pericellular FN (CaFN). In all incubations, highly significant negative linear relationships were found between the numbers of MCs per well and quantities of both SeFN and CaFN after normalization of the data by logarithmic transformation (SeFN: r values > -0.9705; CaFN: r > -0.9620; P < 0.001). Thus, increasing cell densities progressively suppressed ECM formation by MCs. The ECM production was found to be independent of growth activity. AVP significantly increased SeFN (P < 0.05) and decreased CaFN (P < 0.001) in subconfluent cultures; Ang II and 5-HT had no effect. Metabolic labeling with S-35-methionine (18 hr, 200-mu-Ci/ml medium) and 2-D electrophoresis of MC lysates resulted in resolution of > 500 different radiolabeled intracellular proteins in molecular weight from 110 to 20 Kd over an isoelectric interval of 5.0 to 7.0. Computerized video densitometry and scintillation counting of excised spots revealed prominent upregulation of 10 different MC proteins in response to AVP, and enhanced expression of five proteins in response to 5-HT, events characteristic of cellular activation. Ang II caused weakly increased expression of only one protein. The stimulatory effects of AVP and 5-HT on growth and protein synthesis of MCs in-vitro imply a possible in vivo role for these factors in glomerular disease.