[Effects of various growth factors and hormones on clonal rat pulp cells].

Abstract

Effects of transforming growth factor (TGF)-beta, epidermal growth factor (EGF), insulin, 1, 25-dihydroxyvitamin D3 (1, 25 (OH)2D3), and parathyroid hormone (PTH) on the proliferation and differentiation of clonal dental pulp cells of rats were investigated. Interaction between growth factors (TGF-beta and EGF) and two hormones insulin and 1, 25 (OH)2D3, which have been noticed to accelerate the differentiation of the cells, were also studied, and the following results were obtained: 1) TGF-beta decreased alkaline phosphatase (ALPase) activity in a dose-dependent manner, and the inhibitory effect was not blocked by indomethacin, suggesting that the effect of TGF-beta on the cells may not be mediated by prostaglandins. Inhibitory effects of ALPase antagonists (L-phenylalanine, L-homoarginine, levamisole) on the activity were not affected by TGF-beta. TGF-beta showed no evident effect on the DNA synthesis (incorporation of [3H] thymidine) and collagen synthesis (incorporation of [2, 3-3H] proline into the collagenase-digestible protein) of the cells. 2) EGF stimulated the incorporation of [3H] thymidine and inhibited the ALPase activity. The inhibitory effect was not blocked by indomethacin, indicating that the EGF effect is not mediated by prostaglandins. Collagen synthesis was significantly inhibited by EGF. 3) Insulin showed a weak but significant inhibition of the DNA synthesis. Insulin increased the ALPase activity evidently, and accelerated the collagen synthesis significantly. 4) The vitamin 1, 25 (OH)2D3 significantly increased the ALPase activity though no significant changes were observed in the DNA synthesis and collagen synthesis. 5) PTH had no evident effect on the DNA synthesis and ALPase activity, but did tend to accelerate the collagen synthesis. 6) A study on the interaction between insulin and EGF or TGF-beta revealed that the acceleration of DNA synthesis induced by EGF was inhibited when the factor was combined with insulin, and the increase in ALPase activity elicited by insulin was inhibited by EGF and weakened by TGF-beta significantly when these factors were added simultaneously with the insulin. Or viewed another way, the inhibitory effect of EGF or TGF-beta on the ALPase activity was antagonized by insulin. The accelerative action of insulin on collagen synthesis was antagonized by EGF and potentiated by TGF-beta. 7) A study on the interaction between 1, 25 (OH)2D3 and EGF or TGF-beta revealed that 1, 25 (OH)2D3 inhibited the accelerating effect of EGF on the DNA synthesis and that the increasing effect of 1, 25 (OH)2D3 on ALPase activity was strongly inhibited by EGF.(ABSTRACT TRUNCATED AT 400 WORDS)