Relative change in blood volume following administration of hydralazine as monitored by 19F NMR spectroscopy

Measurements of tumor tissue oxygen tension using a time-resolved luminescence-based optical oxylite probe: comparison with a paired survival assay

Recently, a system that measures tissue oxygen tension using time-resolved luminescence-based optical sensors has become available commercially (Oxford Optronix, Oxford, England). Two experiments were conducted using this system. First, the oxygen tension distribution was measured in two tumor lines: a spontaneous mouse fibrosarcoma, FSa-II, and a human squamous cell carcinoma xenograft, FaDu. The area in which the pO(2) was equal to or lower than 2.5 mmHg was defined as the hypoxic lesion, and the hypoxic cell fraction was taken as the fraction of these measurements in a tumor. The measured hypoxic cell fractions were compared with those determined by the paired cell survival assay for tumors of various sizes. Second, the tumor tissue pO(2) was measured continuously after administration of two different anesthetics to evaluate the effect of these drugs on tissue pO(2). Results indicated a good agreement between the hypoxic cell fractions measured by this system and those determined by the paired cell survival curve assay for tumors smaller than approximately 500 mm(3). For tumors larger than approximately 500 mm(3), the hypoxic cell fractions measured by the oxygen probe system were higher than those measured by the paired cell survival assay. This may suggest that the hypoxic cell fraction measured by the oxygen probes included both hypoxic and necrotic areas in large tumors where necrotic lesions occupied a significant portion of the tumor. Continuous measurements of pO(2) after anesthesia (Nembutal, or ketamine plus xylazine) showed a consistent rise in the pO(2) during the first 20-30 min of measurement. Subsequently, the pO(2) values became constant or continued to rise slowly. For comparison, the tumor cell survivals were assayed after a dose of 20 Gy given in air at 5, 20 and 60 min after anesthesia. The result showed a decrease in cell survival only in tumors irradiated 20 min after an injection of Nembutal.

Acute effects of vascular modifying agents in solid tumors assessed by noninvasive laser Doppler flowmetry and near infrared spectroscopy

The potential of noninvasive laser Doppler flowmetry (LDF) and near infrared spectroscopy (NIRS) to detect acute effects of different vascular-modifying agents on perfusion and blood volume in tumors was evaluated. C3H mouse mammary carcinomas (approximately 200 mm(3)) in the rear foot of CDF1 mice were treated with flavone acetic acid (FAA, 150 mg/kg), 5,6-dimethylxanthenone-4-acetic acid (DMXAA, 20 mg/kg), combretastatin A-4 disodium phosphate (CA4DP, 250 mg/kg), hydralazine (HDZ, 5 mg/kg), or nicotinamide (NTA, 500 mg/kg). Tumor perfusion before and after treatment was evaluated by noninvasive LDF, using a 41 degrees C heated custom-built LDF probe with four integrated laser/receiver units, and tumor blood volume was estimated by NIRS, using light guide coupled reflectance measurements at 800+/-10 nm. FAA, DMXAA, CA4DP, and HDZ significantly decreased tumor perfusion by 50%, 47%, 73%, and 78%, respectively. In addition, FAA, DMXAA, and HDZ significantly reduced the blood volume within the tumor, indicating that these compounds to some degree shunted blood from the tumor to adjacent tissue, HDZ being most potent. CA4DP caused no change in the tumor blood volume, indicating that the mechanism of action of CA4DP was vascular shut down with the blood pool trapped in the tumor. NTA caused no change in either tumor perfusion or tumor blood volume. We conclude that noninvasive LDF and NIRS can determine acute effects of vascular modifying agents on tumor perfusion and blood volume.

Effects of vasodilators on the signal intensity of perfluorocarbon monitored by in vivo 19F-NMR spectroscopy

The effects of vasodilators on peripheral vessels were examined by monitoring the 19F-NMR signal of perfluorocarbon in vivo. Nitroglycerin, a venodilator that acts mainly on venous smooth muscle, increased the signal intensity of FC-43, whereas hydralazine, a typical arteriolar dilator that acts on arteriolar smooth muscle, decreased the signal intensity. These results indicate that the in vivo effects of vasodilators on smooth muscles of the venous and arterial systems are reflected by their effects on the signal intensity of FC-43.

Overview of progress in the fluorocarbon approach to in vivo oxygen delivery

The development of fluorocarbon-based oxygen carriers has experienced rapid progress over the past few years. Fluosol has been approved for use during percutaneous transluminal coronary angioplasty (PTCA) for high-risk patients. Its clinical evaluation is being pursued as an adjunct to cancer therapy and for treatment of myocardial infarction in conjunction with thrombolytic therapy. O2-delivery efficacy has been achieved with the development of the new highly concentrated (4 to 5 times more concentrated than Fluosol), fluid, emulsions of perfluorooctyl bromide (perflubron), trade-named Oxygen. The stability of fluorocarbon emulsions has also improved considerably and the new emulsions can be stored unfrozen and are ready for use. The side-effect profile of these emulsions has been characterized as being the normal response of the body's phagocytes to the injection of particles, a response that is considered physiological rather than pathological in nature; it involves some products of arachidonic acid metabolism and can be controlled pharmacologically. Means of further stabilizing fluorocarbon emulsions, involving molecular-diffusion-controlling additives or fluorinated surfactants, including mixed fluorocarbon-hydrocarbon compounds, have been devised. Increased control over in vivo particle recognition, intravascular persistence and side effects, and at adapting emulsion characteristics to specific applications, is being investigated. The range of therapeutic applications is expanding. The concentrated emulsions will be able to serve as a temporary red blood cell substitute in many situations. Acute normovolemic hemodilution with fluorocarbon emulsions, used in conjunction with homologous predonation and other blood-sparing techniques, should afford greater flexibility, increase the margin of safety, and reduce or alleviate the need for autologous blood transfusion during surgical procedures. Fluorocarbon applications in the cardiovascular field include use during PTCA, for cardioplegia and reperfusion, and the treatment of myocardial infarction. Significant tumor growth delay has been achieved when concentrated emulsions are used in conjunction with cancer radio- or chemotherapy. Liquid ventilation has potential as a unique treatment for the adult and infant respiratory distress syndromes and for drug delivery. The radiopaque and versatile perflubron can also be used in contrast agents for diagnosis with computed X-ray tomography, magnetic resonance imaging and ultrasound, allowing the early detection and staging of cancer. Other potential applications investigated include the treatment of cerebral ischemia, organ and limb preservation, use as a tamponade during retinal repair, etc.