, No. Based on these observations, we hypothesized that the tumor interstitial fluid pressure should increase following the onset of angiogenesis.To this end, the relationship between IFP and tumor neo vascularization was determined in the human colon adenocarcinoma implanted in a transparent dorsal skin fold chamber in severe combined immunodeficient mice.Three stages in the development of the tumor neovasculature were char acterized by intravital microscopy.Stage I tumors were avascular, stage was Glimepiride characterized by vascular sprouts and loops, and in stage ifi, the tumor vasculature was completely developed and blood flow was obvious.The IFP was measured with micropipettes and a servonull system.In conclusion, the results demonstrate that Glimepiride avascular tumors have atmo spheric pressures and that tumor interstitial hypertension is associated with the development of the neovasculature.A significant implication of the transmission of the MVP to the interstitial space of tumors is that the IFP should begin to rise following the onset of angiogenesis.During the prevascular stage of primary tumor and micrometastasis development, nutrients are provided to neoplastic cells by preexisting vessels.Further tumor growth is dependent on the formation of new blood vessels from the surrounding vasculature by angiogenesis. The costs of publication of this article were defrayed in part by the payment of page charges.This article must therefore be hereby marked advertisement in accordance with U.The abbreviations used are: IFP, interstitial fluid pressure; MVP, microvascular pressure; SCID, severe combined immunodeficient.The human colon adenocarcinoma were implanted on the striated skin muscle in the dorsal skin fold chamber of SC mice.The tumor chambers were prepared as described previously. In brief, a double layer of skin was sandwiched between two titanium frames.In a previous study, we have shown that in tumors with a completely developed vasculature, the IFP was not modified by the removal of the coverslip. The tumor IFP measured from the skin side before removing the coverslip was similar to measurements made after remov ing the coverslip.The development of the tumor neovasculature was characterized from day to after tumor implantation with an intravital microscope. The left carotid artery was cannulated with PE tubing to monitor the mean arterial blood pressure.The MVP was measured in vessels with diameters between and tm.To verify that the tip of the micropipette was in the lumen of the tumor vessels, fast green was infused via the micropipette.MVP measurements were considered valid when the fast green disappeared rapidly with blood flow following the infusion.In stage I, on day and after tumor implantation the tumor was avascular, and the underlying and peripheral normal vessels were dilated was character ized by vascular sprouts and loops that were evident in the tumor periphery and appeared as dark spots in the center of the tumor, the tumors were fully vascularized, and blood flow was obvious. The distinction between the three stages was based on the morphological characteristics given above.The increase in IFP between stage I and H cannot be ex plained by a change in tumor size since the thickness of the tumor in both stages was comparable.The highest IFP measured in this study was. IFP during the three successive stages of tumor neovascularization in the human colon adenocarcinorna growing in a dorsal skin fold chamber in SCID mice.