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MODULATION OF INSULIN-STIMULATED DNA SYNTHESIS BY CHOLERA TOXIN IN BOVINE MAMMARY FIBROBLASTS

  • Yuh, I.S. (Department of Dairy Science, College of Animal Agriculture Kangwon National University) ;
  • Park, C.K. (Department of Dairy Science, College of Animal Agriculture Kangwon National University) ;
  • Han, J.Y. (Dept. of Animal Science and Technology, Seoul National University) ;
  • Sheffield, L.G. (Dept. of Dairy Science, University of Wisconsin-Madison)
  • Received : 1993.02.26
  • Accepted : 1993.07.08
  • Published : 1993.12.01

Abstract

Bovine fibroblasts were cultured in Dulbecco's Modified Eagle's Medium and then treated with control, insulin (I, $1{\mu}g/ml$), cholera toxin (CT, 0.1-100 ng/ml) or CT (0.1-100 ng/ml) + I ($1{\mu}g/ml$). Cholera toxin, an activator of adenylate cyclase, significantly decreased insulin induced DNA synthesis (p<0.05). The modulation of DNA synthesis apparently involves events occurring in early stage of cell growth, at least between the first 4 and 8 hour of CT treatment. Insulin induced collagen as well as noncollagen synthesis in cell layer, however, these syntheses were reduced by addition of cholera toxin (p<0.05) but were not completely reduced. It is not clear whether the reduction of insulin-induced cell layer collagen or noncollagen proteins by CT is involved in the inhibitory effect on insulin-induced DNA synthesis. However, we could rule out the hypothesis that insulin-induced DNA synthesis is reduced by CT-induced cellular differentiation.

Keywords

Bovine Fibroblast;Cholera Toxin;Insulin;DNA Synthesis