Acute effects of bradykinin on cerebral microvascular permeability in the anaesthetized rat

1. The permeability response to acutely applied bradykinin and [des-Arg9]-bradykinin on single cerebral venular capillaries has been investigated using the low molecular mass fluorescent dyes Lucifer Yellow and Sulforhodamine B with the single vessel occlusion technique. 2. When bradykinin was applied repeatedly for up to 2 h, the permeability increase was small and reversible for concentrations that ranged from 5 nM to 50 microM. 3. The logEC50 of the permeability response to bradykinin was -5.3 +/- 0.15 (logM; mean +/- s.e.m.). This was reduced to -6.37 +/- 0.24 with the angiotensin-converting enzyme inhibitor captopril, to -6.33 +/- 0.19 with the neutral endopeptidase inhibitor phosphoramidon and to -7.3 +/- 0.20 with captopril and phosphoramidon combined. 4. The permeability response to bradykinin was blocked by the bradykinin B2 receptor antagonist HOE 140, by inhibition of the Ca2+-independent phospholipase A2, by the scavenging of free radicals, or by inhibition of both cyclo-oxygenase and lipoxygenase in combination. Block of Ca2+ entry channels with SKF 96365 had no effect on the response. 5. Application of [des-Arg9]-bradykinin also increased permeability over the concentration range 5 nM to 50 microM, with a logEC50 of -5.6 +/- 0. 37. This response was not affected by free radical scavenging, but was completely blocked by the histamine H2 receptor blocker cimetidine. 6. These results imply that the acute permeability response to bradykinin is mediated via the release of arachidonic acid, which is acted on by cyclo-oxygenase and lipoxygenase resulting in the formation of free radicals, and that the response to [des-Arg9]-bradykinin is mediated via histamine.

Sequential development of angiotensin receptors and angiotensin I converting enzyme during angiogenesis in the rat subcutaneous sponge granuloma

1. The vasoconstrictor peptide antiotensin II (AII) can stimulate angiogenesis, an important process in wound healing, tumour growth and chronic inflammation. To elucidate mechanisms underlying AII-enhanced angiogenesis, we have studied a subcutaneous sponge granuloma model in the rat by use of 133Xe clearance, morphometry and quantitative in vitro autoradiography. 2. When injected directly into the sponge, AII (1 nmol day-1) increased 133Xe clearance from, and fibrovascular growth in sponge granulomas, indicating enhanced angiogenesis 6 to 12 days after implantation. This AII-enhanced angiogenesis was inhibited by daily doses (100 nmol/sponge) of the specific but subtype non-selective AII receptor antagonist (Sar1, Ile8)AII, and by the selective non-peptide AT1 receptor antagonists losartan and DuP 532. In contrast, AII-enhanced neovascularization was not inhibited by the AT2 receptor antagonist PD123319, nor was it mimicked by the AT2 receptor agonist CGP42112A (each at 100 nmol/sponge day-1). 3. AI (1 nmol/sponge day-1), the angiotensin converting enzyme (ACE) inhibitors captopril (up to 100 micrograms/sponge day-1) and lisinopril (40 micrograms/sponge day-1), or AII receptor antagonists did not affect angiogenesis in the absence of exogenous AII. 4. [125I]-(Sar1, Ile8)AII binding sites with characteristics of AT1 receptors were localized to microvessels and to non-vascular cells within the sponge stroma from 4 days after implantation, and were at higher density than in skin throughout the study. 5. [125I]-(Sar1, Ile8)AII binding sites with characteristics of AT2 receptors were localized to non-vascular stromal cells, were of lower density and appeared later than did AT1 sites. 6. The ACE inhibitor [125I]-351A bound to sites with characteristics of ACE, 14 days after sponge implantation. [125I]-351A bound less densely to sponge stroma than to skin. 7. We propose that AII can stimulate angiogenesis, acting via AT1 receptors within the sponge granuloma. AT1 and AT2 receptors and ACE develop sequentially during microvascular maturation, and the role of the endogenous angiotensin system in angiogenesis will depend on the balanced local expression of its various components. Pharmacological modulation of this balance may provide novel therapeutic approaches in angiogenesis-dependent diseases.

Innervation and neurokinin receptors during angiogenesis in the rat sponge granuloma

Angiogenesis is an essential component of wound healing and inflammation. In the rat subcutaneous sponge implantation model, angiogenesis can be enhanced by administration of the sensory neuropeptide, substance P. We have used quantitative in vitro receptor autoradiography and immunohistochemistry to investigate the development of endogenous neurovascular regulatory systems in the newly-formed granulation tissue of this model. The fraction of endothelial cells immunoreactive for proliferating cell nuclear antigen, endothelial fractional area, and 133Xe clearance were used as measures of endothelial proliferation, neovascularization, and blood flow, respectively. Endothelial proliferation occurred predominantly in tissues surrounding the sponge, and peaked before neovascularization of sponge stroma and the establishment of sponge blood flow. Substance P-containing sensory nerves and specific, high affinity substance P binding sites with characteristics of neurokinin receptors of the NK1 subclass, were localized to microvessels surrounding the sponge at all time points. Lower density substance P binding sites were localized to newly formed microvessels within the sponge stroma, progressively increasing in density from day 4 to day 14. Nerve fibres were observed in the stroma of only 2 of 6 sponges at day 14, and none at earlier time points. These data support the hypothesis that substance P-enhanced angiogenesis in this model results from a direct action on microvascular NK1 receptors. Neovascularization is a sequential process, with early endothelial proliferation followed by new vessel formation and increased blood flow, with maturation of endogenous neurovascular regulatory systems occurring late in this process in inflamed tissues.

Differential effects of angiostatic steroids and dexamethasone on angiogenesis and cytokine levels in rat sponge implants

1. Subcutaneous implantation of sterile polyether sponges elicited a reproducible neovascular response in rats, as determined by blood flow measurement with a 133Xe clearance technique and confirmed histologically. This model was used to monitor the levels of two cytokines during angiogenesis and to compare the activities of angiostatic steroids and anti-inflammatory steroids. 2. Initial experiments followed the neovascular development over a 20-day period. Daily local injection of hydrocortisone caused a dose-dependent (0.5, 5 and 50 micrograms per sponge) inhibition of the basal sponge-induced angiogenesis. However, daily systemic treatment of hydrocortisone (2, 10 and 50 mg kg-1, s.c.) was less effective at inhibiting angiogenesis, and this inhibition was not sustained by day 20 after sponge implantation. 3. To investigate the involvement of cytokines during the course of angiogenesis, we measured the endogenous levels of tumour necrosis factor-alpha (TNF-alpha) and interleukin 6 (IL-6) in sponge implants. Levels of IL-6 and TNF-alpha peaked at day 7 and day 11 after implantation, respectively. These cytokine levels subsided through the completion of angiogenesis by day 20. 4. Subsequent experiments were carried out over a 14-day period. Among the three angiostatic steroids tested, U-24067 (6 alpha-fluoro-17,21 - dihydroxy-16 alpha-methylpregna -4,9(11)-diene-3,20-dione-21-acetate) showed a dose-dependent inhibition (0.5, 5 and 50 micrograms per sponge per day) of sponge-induced angiogenesis. Tetrahydro-S was also effective at 5 micrograms doses, but medroxyprogesterone failed to affect the angiogenic response. None of these steroids caused atrophies of the spleen and thymus. 5. Daily local injection of dexamethasone (0.5 microgram per sponge) inhibited the basal sponge-induced angiogenesis almost completely. Although higher doses of dexamethasone (5 and 50 micrograms per sponge) did not produce further inhibition of angiogenesis, they caused severe spleen and thymus weight losses, indicative of immunosuppression. 6. At the daily dose of 5 micrograms per sponge, dexamethasone inhibited angiogenesis and produced a marked reduction in the levels of TNF-alpha and IL-6 at day 14. In contrast, hydrocortisone, U-24067 and tetrahydro-S did not influence the levels of TNF-alpha and IL-6. 7. We concluded that the anti-angiogenic activity of angiostatic steroids and anti-inflammatory steroids in the rat sponge model is independent of their ability to reduce the production of TNF-alpha and IL-6. The differential effects of angiostatic and anti-inflammatory steroids suggest that U-24067 and its derivatives may have therapeutic potential in the management of angiogenic diseases such as rheumatoid arthritis.

Comparative studies of the angiogenic activity of vasoactive intestinal peptide, endothelins-1 and -3 and angiotensin II in a rat sponge model

1 The angiogenic activity of four vasoactive peptides with a range of vasodilator and vasoconstrictor properties, i.e. vasoactive intestinal peptide (VIP), endothelin-1, endothelin-3 and angiotensin II, were investigated in a rat sponge model. Neovascularization was assessed by the 133Xe clearance technique and confirmed by histological studies. 2 Daily doses of the vasodilator peptide, VIP (1000 pmol), caused intense neovascularization, but a lower dose (10 pmol) produced no apparent effect. However, the lower dose of VIP, when given with a subthreshold dose of interleukin-1 alpha (0.3 pmol), produced an angiogenic response similar to that seen with the higher dose of VIP. The neovascular response induced by co-administration of VIP and interleukin-1 alpha was inhibited by simultaneous administration of 100 pmol VIP (10-28), a specific VIP receptor antagonist. 3 In contrast, daily doses of 10, 100 or 1000 pmol endothelin-3 (a mixed vasoconstrictor and vasodilator with more marked vasodilator activity) or of 100 or 1000 pmol endothelin-1 (also with mixed activity but with much more pronounced vasoconstrictor response) produced no apparent effect on sponge-induced angiogenesis. 4 The vasoconstrictor peptide, angiotensin II, in daily doses of 1000 pmol, caused an intense neovascularization like VIP but lower doses of angiotensin II (10 or 100 pmol) produced no apparent effect. The lowest dose of angiotensin II (10 pmol) when administered with the subthreshold dose of interleukin-1 alpha (0.3 pmol) had no effect on the basal neovascular response in the sponges. The angiotensin II-induced neovascular response was inhibited by co-administration of 100 nmol of the specific AT1 receptor antagonist, losartan, but not by the AT2 receptor antagonist, PD 123319. 5 These data show that VIP and angiotensin II possess angiogenic activity. However, endothelin-1 and endothelin-3 had no activity at the doses used. Thus the angiogenic response is not related to local vasoconstriction or vasodilatation in the sponges. The blockade of VIP- and angiotensin II-induced angiogenesis at the receptor level suggests that receptor modulation could provide a strategy for the management of angiogenic diseases.

Correlation of 133Xe clearance, blood flow and histology in the rat sponge model for angiogenesis. Further studies with angiogenic modifiers

BACKGROUND

We have previously described a method of quantitating angiogenesis by using a simple 133Xe clearance technique for repeated measurement of relative blood flow changes through s.c. sponge implants over a period of 14 days. The quantitative requirement of this bioassay is that the measurements of 6-minute 133Xe clearance should provide a fast and reliable means to detect relative blood flow changes in the neovasculature, so a more vigorous validation of the use of the 133Xe clearance technique as an indicator of angiogenesis is needed.

EXPERIMENTAL DESIGN

Four different techniques were used: (a) to measure absolute blood flow in the sponges using 113Sn microspheres; (b) to quantitate the levels of hemoglobin and total protein in the implants; (c) to determine the amount of neovasculature in the sponges by the carmine dye method; and (d) to carry out histologic and morphometric analysis of sponge implants. To confirm parallel changes in 133Xe clearance and in the other techniques, the effects of selected angiogenic promoters and inhibitors were also investigated.

RESULTS

There was a good correlation between 133Xe clearance from the sponges and absolute blood flow (r = 0.952, p < 0.01); the levels of hemoglobin (r = 0.982, p < 0.01) and total protein (r = 0.962, p < 0.01); the amount of carmine dye (r = 0.974, p < 0.01); the fibrovascular growth areas (r = 0.992, p < 0.01); and the vascular density (r = 0.997, p < 0.01) in the implants. Daily administration of 3 pmol of IL-1 alpha or IL-8 caused intense neovascularization. When given alone, lower doses of IL-1 alpha (0.3 pmol) or bradykinin (10 pmol) produced no apparent effect. However, co-administration of these doses to a single sponge together caused an increase in the rate of angiogenesis similar to that seen with a higher dose of IL-1 alpha (3 pmol) acting alone. In contrast, daily co-administration of a potent and selective protein kinase C inhibitor, calphostin C (4 micrograms), inhibited the neovascular response elicited by 3 pmol of IL-1 alpha. Furthermore, daily doses of 5 micrograms of dexamethasone for 14 days inhibited sponge-induced angiogenesis.

CONCLUSIONS

The results clearly show that the 133Xe clearance technique not only gives an indication of the rate of perfusion of the sponges with blood but also gives a good estimate of its functional vascularity. Thus, the measurement of 133Xe clearance in the sponge implant provides a simple and objective method for routine studies of modifiers of angiogenesis.

Thymidine phosphorylase is angiogenic and promotes tumor growth

Platelet-derived endothelial cell growth factor was previously identified as the sole angiogenic activity present in platelets; it is now known to be thymidine phosphorylase (TP). The effect of TP on [methyl-3H]thymidine uptake does not arise from de novo DNA synthesis and the molecule is not a growth factor. Despite this, TP is strongly angiogenic in a rat sponge and freeze-injured skin graft model. Neutralizing antibodies and site-directed mutagenesis confirmed that the enzyme activity of TP is a condition for its angiogenic activity. The level of TP was found to be elevated in human breast tumors compared to normal breast tissue (P < 0.001). Overexpression of TP in MCF-7 breast carcinoma cells had no effect on growth in vitro but markedly enhanced tumor growth in vivo. These data and the correlation of expression in tumors with malignancy identify TP as a target for antitumor strategies.

Protein kinase C inhibitor calphostin C prevents cytokine-induced angiogenesis in the rat

A rat sponge implant model was used to examine the role of protein kinase C (PKC) in angiogenesis. Neovascular response was determined by measurements of relative sponge blood flow by a 133Xe clearance technique and confirmed histologically. Morphometric analysis was used to quantitate the amount of fibrovascular growth in the sponges. Daily doses of recombinant human basic fibroblast growth factor (bFGF, 100 ng), tumor necrosis factor-alpha (TNF-alpha, 50 ng), or interleukin-1-alpha (IL-1 alpha, 50 ng) caused neovascular responses that were blocked by daily coadministration of the selective PKC inhibitor, calphostin C (4 micrograms). To confirm that calphostin C was able to inhibit PKC in vivo, its effect on the angiogenic response elicited by the PKC activator, phorbol 12-myristate 13-acetate (PMA, 30 micrograms) was examined. The blood flow and morphometric data clearly showed that the intense neovascularization induced by PMA was totally suppressed by coadministration of calphostin C (4 micrograms). Thus, these results suggest that cytokine-induced angiogenesis may be mediated in part through the activation of PKC and that selective inhibition of this enzyme could have therapeutic benefit in angiogenic diseases.

Suppression of VEGF-induced angiogenesis by the protein tyrosine kinase inhibitor, lavendustin A

1. Vascular endothelial growth factor (VEGF) is a heparin-binding angiogenic factor which specifically acts on endothelial cells via distinct membrane-spanning tyrosine kinase receptors. Here we used the rat sponge implant model to test the hypothesis that the angiogenic activity of VEGF can be suppressed by protein tyrosine kinase (PTK) inhibitors. 2. Neovascular responses in subcutaneous sponge implants were determined by measurements of relative sponge blood flow by use of a 133Xe clearance technique, and confirmed by histological studies and morphometric analysis. 3. Daily local administration of 250 ng VEGF165 accelerated the rate of 133Xe clearance from the sponges and induced an intense neovascularisation. This VEGF165-induced angiogenesis was inhibited by daily co-administration of the selective PTK inhibitor, lavendustin A (10 micrograms), but not its negative control, lavendustin B (10 micrograms). Blood flow measurements and morphometric analysis of 8-day-old sponges showed that lavendustin A reduced the 133Xe clearance of VEGF165-treated sponges from 32.9 +/- 1.5% to 20.9 +/- 1.6% and the total fibrovascular growth area from 62.4 +/- 6.1% to 21.6 +/- 6.8% (n = 12, P < 0.05). 4. Co-injection of suramin (3 mg), an inhibitor of heparin-binding growth factors, also suppressed the VEGF165-elicited neovascular response. In contrast, neither lavendustin A nor suramin produced any effect on the basal sponge-induced angiogenesis. 5. When given alone, low doses of VEGF165 (25 ng) or basic fibroblast growth factor (bFGF; 10 ng) did not modify the basal sponge-induced neovascularisation. However, co-administration of these two peptides to a single sponge together caused a significant increase in the rate of 133Xe clearance and angiogenesis similar to that seen with the high dose of VEGF165 (250 ng) acting alone. This VEGF/bFGF neovascular response was also blocked by daily co-administration of lavendustin A (10 jig),suramin (3 mg) or a monoclonal anti-bFGF antibody (DG2, I jig), but not lavendustin B (10 g).6 These results suggest that selective inhibition of PTK could have therapeutic potential in angiogenic diseases where VEGF plays a dominant role. Furthermore, blockade of the angiogenic activity of VEGF and VEGF,/bFGF by suramin reveals an alternative strategy in angio suppression.

A structure-activity analysis of antagonism of the growth factor and angiogenic activity of basic fibroblast growth factor by suramin and related polyanions

The ability of a series of polysulphonated naphthylureas structurally related to suramin to inhibit basic fibroblast growth factor (bFGF) or serum-stimulated growth of endothelial cells [either large vessel, human umbilical vein endothelial cells (HUVEC) or microvascular, bovine adrenal capillary endothelial (BACE) cells] and angiogenesis in vivo has been examined. The polyanions encompassed two main structural variations, namely the number of aromatic amide groups intervening between two terminal naphthyl rings and/or variation in the substitution pattern of the naphthyl rings. The polyanions were either inactive (group I) or inhibited (group II) bFGF-stimulated uptake of [3H]methylthymidine by BACE cells. Group I compounds shared a common structural feature in that they were simple binaphthyl-substituted ureas. In contrast, group II compounds all had an extended multiple ring structure with at least two aromatic groups intervening between the two terminal naphthyl rings. Compounds with either two or four intervening groups were equipotent in blocking bFGF in vitro. However, compounds with two bridging aromatic groups were 5- to 10-fold less toxic than suramin in mice, suggesting a potential for an improved therapeutic ratio. The ability of the polyanions to block bFGF-driven endothelial cell proliferation in vitro correlated with antiangiogenic activity in vivo as shown by use of the rat sponge angiogenesis model. These observations could substantially widen the anti-tumour therapeutic opportunities for this class of compound.

Inhibition of angiogenesis in rats by IL-1 receptor antagonist and selected cytokine antibodies

Daily administration of 50 ng recombinant human interleukin 1-alpha (IL-1 alpha), 25 ng IL-8, 50 ng tumor necrosis factor-alpha (TNF-alpha), or 100 ng basic fibroblast growth factor (bFGF) caused intense neovascularization in a rat sponge model. These cytokine-induced neovascular responses were inhibited by coadministration of IL-1 receptor antagonist (IL-1ra; 50 micrograms), IL-8 antiserum (IL-8-AS; 1: 1000), TNF-alpha antibody (TNF-AB; 500 ng), or a monoclonal antibody to bFGF (DG2; 1000 ng), respectively. These data suggest that it is possible to manipulate the angiogenic response elicited by a defined cytokine by its receptor antagonist or neutralizing antibody. In the absence of exogenous cytokines, the sponge-induced angiogenesis was profoundly suppressed by dexamethasone (5 micrograms/day), but not modified by IL-1ra, IL-8-AS, TNF-AB, and DG2 alone. However, the combination of these four reagents was able to inhibit the sponge-induced neovascular response almost completely. These findings provide direct evidence that IL-1 alpha, IL-8, TNF-alpha and/or bFGF have an intrinsic role in angiogenesis. Further work is necessary to characterize the profile of these cytokines during angiogenesis and to elucidate the nature of their interactions.

Stimulation of angiogenesis by substance P and interleukin-1 in the rat and its inhibition by NK1 or interleukin-1 receptor antagonists

1. Daily administration of 1 nmol substance P or 3 pmol recombinant human interleukin-1 alpha (IL-1 alpha) caused intense neovascularization in a rat sponge model of angiogenesis. Lower doses of substance P (10 pmol) or IL-1 alpha (0.3 pmol) were ineffective when given alone. When combined at these low doses, substances P and IL-1 alpha interacted to produce an enhanced neovascular response. 2. By use of selective tachykinin NK1, NK2 and NK3 receptor agonists, ([Sar9,Met(O2)11]substance P, [beta-Ala8]neurokinin A(4-10), Succ-[Asp6,MePhe8]substance P(6-11) (senktide), respectively), it was established that the activation of NK1 receptors is most likely to mediate the angiogenic response to substance P in this model. 3. The angiogenic activity of substance P and IL-1 alpha (10 pmol and 0.3 pmol day-1, respectively) was abolished by co-administration of (i) the selective peptide NK1 receptor antagonist, L-668,169 (1 nmol day-1), (ii) the selective non-peptide NK1 receptor antagonists, RP 67580 and (+/-)-CP-96,345 (both at 1 nmol day-1) or (iii) the IL-1 receptor antagonist, IL-1ra, (50 micrograms day-1). In contrast, the selective NK2 receptor antagonist, L-659,874 (1 nmol day-1) was ineffective. 4. The angiogenic action of substance P and IL-1 alpha was resistant to modification by mepyramine (1 nmol day-1) and/or cimetidine (10 nmol day-1), indomethacin (7 nmol day-1) or the platelet-activating factor (PAF) antagonist, WEB-2086 (22 nmol day-1), indicating that histamine, prostaglandins and PAF are not likely to be involved in this neovascular response. 5. The inhibition of the substance P/IL-1 angiogenic response by selective NK1 receptor antagonists or by an IL-1 receptor antagonist demonstrates that angiosuppression can be achieved by blocking the activity of angiogenic factors at the receptor level.

[Leu8]des-Arg9-bradykinin inhibits the angiogenic effect of bradykinin and interleukin-1 in rats

1. Subcutaneous implantation of sterile polyether sponges in rats elicited a reproducible neovascular response over 14 days, as determined by measurements of relative sponge blood flow by a 133Xe clearance technique. The angiogenic response was verified by quantitation of haemoglobin contents and histological evaluation of vascularized sponges. 2. Daily administration of 1 nmol of bradykinin (BK) into the implants significantly enhanced the basal sponge-induced neovascularization, leading to higher 133Xe clearance values, increased haemoglobin contents, cellularity and vascularity. 3. When given alone, lower doses of BK (10 pmol) or recombinant human interleukin-1 alpha (IL-1 alpha, 0.3 pmol) produced no apparent effects on the basal sponge-induced angiogenesis. However, co-administration of these two peptides produced an angiogenic response similar to that elicited by 1 nmol of BK. 4. The BK/IL-1 alpha-induced neovascularization was abolished by the bradykinin B1 receptor antagonist, [Leu8]des-Arg9-BK (1 nmol day-1), but not by the B2 receptor antagonist Ac-D-Arg-[Hyp3, D-Phe7, Leu8]-BK (1 nmol day-1). 5. Thus, if such interaction between BK and IL-1 alpha contributes to the excessive neovascularization in chronic inflammatory diseases, the blockade of B1 receptors may provide an effective treatment.

Interleukin-8 stimulates angiogenesis in rats

To test the hypothesis that the cytokines interleukin-6 (IL-6) and IL-8 may play regulatory roles in the aberrant neovascularization in chronic inflammatory diseases, we examined their effects in a rat sponge model and compared their actions with those of IL-1 and tumor necrosis factor-alpha (TNF-alpha). Daily doses of 3 pmol IL-8, IL-1, TNF-alpha, but not IL-6, significantly accelerated the sponge-induced angiogenesis. Although lower doses (0.3 pmol) of these cytokines were inactive, IL-1 acted synergistically with subthreshold daily doses (10 pmol) of substance P (SP) and bradykinin (BK) to produce an intense angiogenic response. In contrast, IL-8 only interacted positively with IL-1, but not TNF-alpha, SP, or BK. There was no synergism or antagonism between IL-6 and SP. These results demonstrate the discrete interactions between angiogenic factors and cytokines in chronic inflammation and suggest that the sponge model is a good means for the study of such interactions.

BW12C: effects on tumour hypoxia, tumour thermosensitivity and relative tumour and normal tissue perfusion in C3H mice

BW12C (5-[2-formyl-3-hydroxypenoxyl] pentanoic acid) is an agent which stabilises oxyhaemoglobin and thus reduces oxygen delivery to tissues. It is of interest as a possible potentiator of bioreductive agents and/or hyperthermia. The increases in radiobiological hypoxic fraction of RIF-1 and KHT tumours 30 min after 70 mg kg-1 BW12C i.v. were measured and shown to be similar; factors (+/- 2 s.e.) ranged from 3.87 (2.84-5.29) to 5.92 (1.92-18.2) despite the large variation in initial hypoxic fraction, from 0.30 (0.18-0.50) % for RIF-1 intramuscularly in the leg to 16.3 (14.7-18.1) % for subcutaneous KHT flank tumours. Thermosensitivity of intramuscular KHT leg tumours was not enhanced by 70 mg kg-1 BW12C 30 min before heating at 43 degrees C, 43.5 degrees C or 44 degrees C, assayed by regrowth delay. The effect of 70 mg kg-1 BW12C on relative tissue perfusion (RTP), assayed by 86Rb extraction, was measured from 0.5 h to 6 h after treatment. After 1 h RTP (+/- 2 s.e.) in RIF-1 tumours was reduced to 84 +/- 5.7% and 68 +/- 9.6% of control in leg and flank tumours respectively, and to 86 +/- 6.4% in leg muscle while flank skin RTP was unaltered at 109 +/- 8.6%. There were substantial increases in kidney (149 +/- 10.7%) spleen (173 +/- 22.1%) and lung (128 +/- 10.4%) at 1 h but in liver there was a decrease at 2 h to 85 +/- 8.4%. Dose response studies showed that the threshold dose for reduction of tumour RTP is between 55 and 70 mg kg-1, but perturbations in normal tissue RTP occur at lower doses, e.g. 40 mg kg-1 for spleen. BW12C had minimal effects on renal function measured by 51CrEDTA clearance. The data as a whole indicate that reduction in tumour perfusion is likely to be an important determinant in the increase in tumour hypoxia induced by BW12C.

A study of the mechanism of hydralazine enhancement of thermal damage in the KHT tumour

The mechanism of the potentiation of thermal damage by hydralazine (HDZ) has been investigated. Using the KHT sarcoma in the leg of C3H mice, it was shown that 5 mg/kg of HDZ given i.v. 15-20 min before irradiation or heat exposure: (i) increased the radiobiological hypoxic fraction from 1 to 32%; (ii) produced a greater than additive growth delay when combined with heating for 30 min at either 43 or 43.5 degrees C, or 60 min at 43 degrees C; (iii) produced only additive cell killing when combined with 30 min heating at 43, 43.5, or 44 degrees C, assayed by clonogenic cell survival immediately or 24 h after treatment; and (iv) produced a prolonged (greater than 72 h) reduction in relative tissue perfusion (RTP) in the tumour when combined with heating for 30 min at 43.5 degrees C. The effects of HDZ or heat alone lasted for less than 24 and 48 h, respectively. The RTP in skin was unaffected by either agent or combination of agents at the times assayed. The results show that this 30-fold increase in hypoxia does not increase the intrinsic thermosensitivity of KHT tumour cells, and that the prolonged reduction in RTP caused by the combined treatment is probably responsible, at least in part, for the greater than additive component of the measured growth delay in this system. The data suggest that non-perfused tumour vessels are more heat sensitive than perfused vessels.

The effects of radiotherapy on the immune system of patients with nasopharyngeal carcinoma

We report on 123 patients with nasopharyngeal carcinoma whose immune status was measured at the time of diagnosis, the day radiotherapy was completed, and then 2-3 months and 6-8 months after completion of radiotherapy. Immunological tests performed included the lymphocyte transformation test, the erythrocyte-rosette formation test (ERFT), the 29 degrees C erythrocyte-rosette formation test (29 degrees C ERFT), lymphocyte counts (lymphocytes/mm3 and percentage of lymphocytes), levels of serum immunoglobulins (IgG, IgA, IgM), complement (C3) and circulating immune complexes (CIC), the antinuclear antibody test and a skin test using phytohaemagglutinin (PHA). There were statistically significant differences in all tests (except C3) between patients and normal controls. Marked differences were seen in the lymphocyte count, ERFT, and 29 degrees C ERFT after radiotherapy (p less than 0.01). The diameters of induration of the PHA skin tests were less than those before radiotherapy (p less than 0.01). There were higher incidences of recurrence and metastases in the patients with high levels of CIC and low numbers of lymphocytes in the peripheral blood after radiotherapy. Cellular immunity remained at a low level 8 months after radiotherapy.