[Intravital observations on the development of the tumor vascular system in rats]

By using transparent chambers in rats, it proved possible to observe directly the normal vascular pattern and early neovascular response to solid tumor growth at high magnification. Morphologic studies of the vascularization patterns were performed daily by construction of photomontages from color instant film taken with a Polaroid camera. Noteworthy results obtained in this study were: In the normal subcutaneous tissue within the chamber, the main vascular pattern was similar to that described by Nicoll and Webb, showing the so-called "arcuate arteriolar pattern". The thoroughfare channel reported by Chambers and Zweifach was also observed. The establishment of new functional capillaries was observed within 2 weeks following the implantation of AH109A and AH272 tumors. The sprouts of newly formed vessels were seen originating at the arterial ends of the host capillaries, where the blood velocity was relatively high. The formation of intricate networks in the tumor occurred easily in a haphazard way; the three modes of network formation observed were sprouting, cross-connection and splitting. Progressive dilatation and tortuosity were observed in the preexisting vessels, especially capillaries and venules, in the neighborhood of the tumor implant. The arterioles, however, remained little altered and in a location almost identical to that at the time of tumor implantation. The vascular systems in the tumors were proved to parallel those in the normal organs from which they originated, from the microfocus stage to the large tumor stage. An understanding of the differences in the vascular architecture between normal and tumor tissue seems to be essential in order to elucidate the mechanism of enhancement of therapeutic effect by angiotensin II induced hypertension chemotherapy.