Prostaglandins fail to elevate cyclic AMP levels in mouse epidermis in vivo and in vitro

Effect of inflammation upon human gingival cyclic AMP metabolism

The effect of the increasing degree of human gingival inflammation on adenylate cyclase (basal, fluoride stimulated) and low Km and high Km cAMP phosphodiesterase activities were evaluated in separate studies. Human gingival biopsies were classified by the Löe Bleeding Index as mildly, moderately, and markedly inflamed. Basal and F- stimulated adenylate cyclase (cAMP synthesis) activities were found to be unaltered by the increasing degree of inflammation when the data were expressed on either a mg wet wt, or mg protein basis. A significant loss of F- stimulated adenylate cyclase (mg protein) activity was observed in the moderately inflamed group when the data were compared with either the mildly or markedly inflamed groups of tissue. The low Km, and high Km cAMP phosphodiesterase activities (cAMP degradation) were found to be unaffected by gingival inflammation. This suggests that neither cAMP synthesis, nor degradation are stimulated in human gingiva by inflammation.

2,3,7,8-Tetrachlorodibenzo-p-dioxin: examination of biochemical effects involved in the proliferation and differentiation of XB cells

XB, a cell line derived from a mouse teratoma, differentiates into stratified squamous epithelium when incubated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). To examine the possible biochemical mediators of this response, we compared the effects produced by TCDD to those elicited by other compounds which stimulate epidermal proliferation and/or differentiation in mice. XB/3T3 cultures keratinize when incubated with cholera toxin, epidermal growth factor (EGF), or TCDD, but not 12-0-tetradecanoylphorbol-13-acetate (TPA). Incubation of XB cells with TCDD (10(-9)M) for 48 hours produces a 20% increase in thymidine incorporation, a response which is neither as large nor as rapid as that produced by cholera toxin, TPA, or EGF. Although both cholera toxin and TCDD stimulate differentiation and thymidine incorporation in XB/3T3 cultures, cholera toxin increases cAMP 30-fold in these cells, while TCDD does not affect cAMP accumulation at any of the times studies (15 min to 120 hours). Inhibitors of arachidonic acid metabolism, which block epidermal proliferative responses to TPA in vivo, do not prevent the differentiation of XB cells in response to TCDD. In XB/3T3 cultures, TPA stimulates arachidonic acid release at all times tested (1,6, and 24 hours) and increases the incorporation of 32Pi into total phospholipids and phosphatidylcholine after 3 hours. In contrast, TCDD affects neither arachidonic acid release nor the turnover of phosphatidylinositol or phosphatidylcholine at any of the times tested. Although we examined biochemical effects which have been suggested as part of the mechanism of TCDD and which are produced by other epidermal proliferative compounds in XB cells, no mediator of the TCDD-produced differentiation of XB/3T3 cultures was observed.