| Abstract: | Modulation of the intracellular concentration of cyclic AMP has been associated with a regulatory role in cell division, cell morphology, and physical properties of the plasma membrane. Untransformed rat kidney cells in culture exhibit epitheloid morphology, high intracellular cyclic AMP levels, and contact inhibition of growth. Untransformed rat kidney cells transformed with the Kirsten murine sarcoma virus exhibit a low cyclic AMP content, rapid growth rate, and a loss of contact inhibition. Scanning electron microscopy reveals a distinctive difference in the surface structure of the two cell types during Gl of the cell cycle. The surface of the transformed cell is covered with microvilli while its untransformed counterpart is devoid of microvilli. The presence of microvilli can be controlled as a function of temperature by two temperature-sensitive mutants of the Kirsten sarcoma virus (ts6t6 and ts371 cl 5). In the ts6t6 mutant, growth at 32 degrees C results in a low cyclic AMP content and the presence of microville, while growth at 39 degrees C results in a high cyclic AMP content and a decrease in microvilli. The opposite effect is seen with the ts371 cl 5 mutant. Correlation of cyclic AMP content with the presence of microvilli suggests that this surface phenomenon is a function of cyclic AMP concentration. |
