In 15 women with PR (primary Raynaud's) disease and in 15 matched control women, ACh (acetylcholine) was delivered by iontophoresis to the dorsum of the finger (seven 20 s pulses of 0.1 mA, followed by one 20 s pulse of 0.2 mA, applied at 60 s intervals). Cutaneous RCF (red cell flux) was recorded from the same site by the laser Doppler technique. ACh evoked progressive increases in RCF that were comparable in pre- and post-menopausal women with PR [maxima of 294±113 and 259±59 pu (perfusion units) respectively, n =7 and 8 respectively], and in pre-menopausal controls (225±92 pu, n =7), but smaller in post-menopausal controls (140±63 pu, n =8; P <0.05). Aspirin (600 mg, orally), a COX (cyclo-oxygenase) inhibitor, potentiated the ACh-evoked dilator responses in pre- and post-menopausal women with PR (343±129 and 311±48 pu respectively) and post-menopausal controls (277±124 pu; P <0.05), but had no effect in pre-menopausal controls (225±92 pu). These results suggest that vasoconstrictor COX products limit ACh-evoked endothelium-dependent cutaneous dilatation in the digits in pre- and post-menopausal women with PR and in post-menopausal, but not pre-menopausal, control women. We propose that PR disease is associated with abnormality in the ability of oestrogen to modulate the synthesis of endothelium-dependent vasodilator and/or vasoconstrictor COX products.

In healthy young men (age, 20–22 years), we tested the role of prostanoids produced by the COX (cyclo-oxygenase) pathway in cutaneous vasodilatation evoked in the finger by ACh (acetylcholine). To this end, changes in cutaneous RCF (red cell flux), recorded by the laser Doppler technique, evoked by a series of iontophoretic pulses of ACh were tested before and after oral aspirin (600 mg). Increases in RCF produced by successive pulses of ACh up to a mean change of 125.5±11.8 PU (perfusion units) were potentiated 30 min after aspirin (160.0±12.4 PU; P <0.05). By contrast, aspirin had no effect on increases in RCF evoked by iontophoretic application of the NO (nitric oxide) donor and endothelium-independent dilator sodium nitroprusside (mean increases in RCF were 73.8±9.8 PU before and 79.1±12.2 PU after aspirin). The ACh-evoked increases in RCF were also potentiated 3 h after oral administration of the antioxidant vitamin C (1000 mg; 139.1±15.4 PU before and 170.5±13.5 PU after vitamin C; P <0.05). We propose that, in healthy young men, cutaneous vasodilatation evoked in the finger by the endothelium-dependent dilator ACh is limited by constrictor products of the COX pathway, including PGH 2 (prostaglandin H 2 ), TXA 2 (thromboxane A 2 ) and/or superoxide anions. This effect of the COX products may be an early marker of the increased risk of cardiovascular disease in men compared with women.

Chronic leg ulceration is a major cause of morbidity in homozygous sickle cell (SS) disease in Jamaica. These ulcers have features in common with venous ulcers in patients with a normal haemoglobin genotype (AA). Thus we sought to determine whether there is abnormal venous function in the legs of patients with SS disease who have ulcers. Experiments were performed on 15 SS patients with ulcers, and on 15 SS patients and 15 AA subjects with no history of leg ulcers. Changes in venous blood volume of the bottom one-third of the leg induced by venous occlusion and release were studied by air plethysmography, providing indices of segmental venous capacitance (SVC), maximal venous outflow (MVO) and venous emptying time (VET). The changes in volume (ambulatory volume change; AVC) induced by a period of leg exercise were also measured at the ankle (AVCa) and calf (AVCc); venous refilling times at these sites (RTa and RTc respectively) were also measured. Finally, cutaneous red blood cell flux recovery time (FRT) after ankle exercise was assessed by laser Doppler flowmetry. Measurements were also made of haematological variables. SVC, MVO and VET did not differ between the groups, indicating no deep venous obstruction in the SS patients with ulcers. AVCc, AVCa and RTc did not differ among the three subject groups. However, compared with AA subjects, SS patients with ulcers had reduced RTa and FRT. Moreover, RTa and FRT were further shortened in SS patients with ulcers relative to SS patients without ulcers. Since the levels of anaemia were similar in SS patients with and without ulcers, these differences cannot be attributed to differences in arterial flow secondary to anaemia. These results suggest abnormal venous function in SS patients with ulcers, relative to both AA subjects and SS patients without ulcers. We propose that there is incompetence of venous valves draining the ankle region of SS patients with ulcers: the consequent raised venous pressure contributes to the slow healing and, possibly, to the onset of leg ulceration in SS disease.

In control subjects and in subjects with primary Raynaud's disease, sudden sound evokes the pattern of the alerting response, which includes cutaneous vasoconstriction and vasodilatation in forearm muscle. However, whereas this pattern of response habituates on repetition of the sound stimulus in control subjects, both cutaneous vasoconstriction and muscle dilatation persist in subjects with primary Raynaud's disease. The aim of the present study was to test whether a similar disparity exists between control subjects and those with primary Raynaud's disease for the response to mild cool stimuli, and whether the cutaneous response is accompanied by the release of endothelin-1 (ET-1). In nine subjects with primary Raynaud's disease and in nine matched controls, the left hand was placed in cool water at 16 °C for 2 min five times on each of three experimental sessions on days 1, 3 and 5, with blood being taken from the venous drainage of the cooled hand before and at the end of the second session. In response to the first cool stimulus in Session 1, the subjects with primary Raynaud's disease showed a decrease in digital cutaneous vascular conductance (DCVC) in both the right and left hands, as indicated by a laser Doppler recording of erythrocyte (red cell) flux divided by arterial pressure, and six of the nine subjects showed an increase in forearm vascular conductance (FVC), as indicated by forearm blood flow measured by plethysmography divided by arterial pressure. On repetition of the stimulus in Session 1, there was no change in the magnitude of the increase in FVC, but the evoked decreases in DCVC became more prolonged in both the right and the left hand. Similar responses occurred in Sessions 2 and 3; in Session 2, the ET-1 concentration increased from a baseline value of 2.15±0.26 fM to 2.72±0.37 fM after five stimuli. There was no habituation of the increase in FVC over Sessions 1, 2 and 3, judging from the mean changes in each session. Control subjects also showed a decrease in DCVC in both hands, and in eight out of nine subjects there was an increase in FVC in response to the first cool stimulus in Session 1. However, on repetition of the stimulus in Session 1, the increase in FVC habituated, while there was no prolongation of the decrease in DCVC; in addition, the ET-1 concentration did not change in Session 2 in response to the stimulus (2.07±0.28 compared with 2.29±0.30 fM). Further, the increase in FVC habituated over the three sessions, such that there was a mean decrease in FVC in Session 3. These results indicate that, in subjects with primary Raynaud's disease, there is impairment of the ability of the central nervous system to allow habituation of the cardiovascular components of the alerting response evoked by mild cooling, as with the response to sound. We propose that persistence of the cutaneous vasoconstriction of the alerting response, coupled with increased release of ET-1 secondary to vasoconstriction, prolongs such vasoconstriction and eventually leads to vasospasm.

1. The vasospasm of primary Raynaud's disease can be triggered by acute emotional stress. We have studied the pattern of cardiovascular response evoked by acute emotional stress, a sound stimulus of 90 ;dB, 2 ;kHz for 30 ;s, in eight subjects with primary Raynaud's disease and in eight age- and sex-matched controls, the sound being repeated five times on each of days 1, 3 and 5. 2. In controls, the first sound evoked the pattern of the alerting response that is characteristic of acute emotional stress: a rise in arterial pressure and heart rate, a decrease in vascular conductance in the cutaneous circulation of the digit, assessed by laser Doppler recording of erythrocyte (red cell) flux in the digit divided by arterial pressure, and an increase in forearm muscle vascular conductance, assessed from forearm blood flow recorded by venous occlusion plethysmography divided by arterial pressure. 3. In the subjects with primary Raynaud's disease, baselines of arterial pressure, digital cutaneous vascular conductance and forearm vascular conductance were not significantly different from those of the controls and they too showed the alerting response to the first sound, the magnitudes of the changes being comparable to those of the controls. 4. In both the controls and subjects with primary Raynaud's disease, the evoked responses were consistent on repetition of the sound on day 1. In contrast, judging from the means of the changes evoked on each day, the controls showed habituation of the individual components of the alerting response over days 1, 3 and 5, whereas the subjects with primary Raynaud's disease showed no habituation of either the forearm muscle vasodilatation or the digital vasoconstriction. Conversely, the decrease in digital cutaneous vascular conductance evoked by a single deep breath was fully reproducible in both controls and subjects with primary Raynaud's disease when tested at the beginning and end of each experimental day. 5. These results allow the novel conclusion that subjects with primary Raynaud's disease have an abnormality of the central neural modulation of the brain stem areas that integrate the cardiovascular components of the alerting response to acute emotional stress, such that habituation of the vasodilator and vasoconstrictor components of the response on repetition of the stimulus is impaired. We propose that such persistence of vasoconstrictor responses to stressful stimuli predisposes to vasospasm, particularly if neurally mediated vasoconstriction is reinforced by locally released vasoconstrictor factors.

1. In homozygous sickle cell (SS) disease, skin cooling is a common precipitating factor of the painful crisis which is associated with avascular necrosis of active bone marrow. Since skin cooling does not directly induce sickling, we have investigated the nature of the reflex vascular responses to mild cooling in SS patients in a steady state of the disease and compared them with their history of painful crises. 2. Experiments were performed in Jamaica on 60 male SS patients and 30 matched control subjects with normal haemoglobin (AA) genotype. Forearm blood flow (FBF) was measured by venous occlusion plethysmography and mean arterial pressure (MAP) by a Finapres device: forearm vascular resistance (FVR) was calculated as MAP/FBF. Cutaneous erythrocyte flux in forearm and hand was monitored by a laser Doppler meter. The contralateral hand was immersed in cool water at 16°C for 2 min, 6 times, at random intervals of 0.5–3 min. 3. The first cool immersion evoked an increase in MAP, cutaneous vasoconstriction and a net increase in FVR in both AA and SS subjects. However, the direction of change in FVR varied between individuals such that 18 AA subjects showed an increase in FVR (constrictor group) while 12 showed a decrease in FVR, indicating vasodilatation in forearm muscle (dilator group). In contrast, 50 SS subjects showed an increase in FVR and only 10 showed a decrease in FVR. The proportion of subjects who showed net vasoconstriction was significantly greater in the SS than in the AA group (83% versus 60%, P = 0.03, χ 2 test). 4. By the sixth cool stimulus, the ‘dilator’ group of AA subjects showed no change in FVR while the ‘dilator’ group of SS patients showed an increase in FVR. We suggest that forearm muscle vasodilatation was the characteristic component of the alerting/defence response to novel or noxious stimuli which habituates on repetition. 5. In the whole group of SS patients, baseline values of cutaneous vascular resistance and FVR increased between stimuli, indicating persistent vasoconstriction, and the sixth cool stimulus still evoked cutaneous vasoconstriction and a net increase in FVR. In contrast, AA subjects showed an increase in baseline FVR between stimuli, but the sixth cool stimulus had no significant effect on cutaneous vascular resistances, or FVR. 6. In SS patients there were no associations between the direction of change in FVR evoked by the first cool stimulus and forearm circumference or skinfold thickness, concentrations of haemoglobin or fetal haemoglobin. However, the frequency of painful crises was significantly greater in the ‘constrictor’ group than in the ‘dilator’ group (0.36 versus 0.12/year, P = 0.04, Mann-Whitney test). 7. These results indicate that the primary reflex vasoconstrictor response evoked by mild cooling is stronger and more persistent in SS patients than in AA subjects and is particularly strong in SS patients who are most prone to painful crises. The results are consistent with the hypothesis that skin cooling may precipitate the painful crisis by causing reflex vasoconstriction in muscle, and possibly in bone marrow, so diverting blood flow away from the active marrow.

1. Laser Doppler flowmetry has been used to study changes in cutaneous erythrocyte flux produced in the hand (i) on successive immersion of the contralateral hand in water at 20°C (cold test) and then in water at 0–4°C (cold pressor test), and (ii) by mental arithmetic. 2. In 11 subjects, placing the right hand in water at 20°C for 2 min induced a significant decrease in cutaneous erythrocyte flux in the contralateral hand and a significant fall in mean arterial pressure. Cutaneous vascular resistance, calculated as arterial pressure/cutaneous erythrocyte flux, showed no significant change. Thus, the decrease in erythrocyte flux was apparently due to a fall in perfusion pressure. 3. Subsequent immersion of the right hand in water at 0–4°C for 2 min caused a significant decrease in erythrocyte flux in the contralateral hand and a significant rise in mean arterial pressure. It is concluded that the cold pressor response evoked from one hand elicited a substantial reflex vasoconstriction in the skin of the other hand; accordingly, calculated cutaneous vascular resistance increased significantly. 4. Eight subjects performed mental arithmetic for two periods of 2 min separated by a rest period of 2 min. By the end of the second minute of each period of mental arithmetic there was a significant decrease in erythrocyte flux. Mean arterial pressure increased significantly in the first period only, but calculated cutaneous vascular resistance increased in both periods, consistent with cutaneous vasoconstriction. 5. The cold pressor test and mental arithmetic are aversive stimuli that evoke the characteristic pattern of the alerting or defence response which includes splanchnic vasoconstriction and muscle vasodilatation. Previous studies on the cutaneous vascular component of this response have yielded equivocal results. The present study provides firm evidence that it includes cutaneous vasoconstriction, at least in the hand.