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Disparate effects of vasoactive drugs on large artery compliance
Abstracts~Netherlands Journal af Medicine 48 (1996) A51-AIO0 spirit (OR 4.0, P = 0.005). After adjustment for total cholesterol, blood pressure, smoking, and independent psychological factors, wine lost its significance (OR 0.4, P = 0.17), whereas the OR for spirit even rose (OR 6.0, P = 0.01). The beneficial effect of wine may be an expression of a relatively low level of life stress. Alcohol itself is not protective but rather a strong risk factor for CHD.
95. Effects of ageing on wall properties of different large arteries. J.J. Spek, J.A. Staessen t, A.P.G. Hoeks 2, H.A.J. Struijker Boudier, L.M.A.B. Van Bortel. Departments of Pharmacology and 2 Biophysics, Cardiovascular Research Institute, University of Limburg, Maastricht, Netherlands. 1Hypertension Unit, University of Leuven. Leuven, Belgium. Compliance (CC) and distensibility (DC) are vessel wall properties of large arteries. It is thought that impaired large artery properties are related to an increased cardiovascular risk. This study investigates the influence of age on the wall properties of the elastic common carotid artery (CCA) and the muscular brachial (BA) and femoral (FA) arteries. 175 persons, who did not use vasoactive mediation, were divided into 5 age-decades (20-29 yr up to 60-69 yr). In these subjects diameter (D) and change in D during the heart cycle were measured non-invasively with a vessel wall movement detector system. From these data and pulse pressure (Ap; Dinamap) DC and CC were calculated. Data are mean-+ SD. Mean arterial pressure was 82 4-1 mmHg in the 3rd decade and 86 4- 1 mmHg in the 7th decade. In the 3rd decade D of CCA was 6.30 -+0.70 mm, DC was 32.3 _+8.1 I0- 3/kPa, CC was 1.02_+0.36 mm2/kPa. With ageing there was a gradual increase in D (7th decade: +21%) and decrease in DC and CC (7th decade: DC - 5 1 % ; CC - 2 9 % ) of CCA. D of FA was 8.47_+ 1.33 mm in the 3rd decade. DC was 15.3_+5.8 10-3/kPa, CC was 0.83_+0.30 mm2/kPa. Ageing resulted also in an increase in D, which mainly occurred in the 5th decade (5th decade + 11%, 7th decade + 15%). There was also a decrease in DC and CC of FA, mainly in the 4th decade (DC 4th decade - 28%, 7th decade - 4 5 % ; CC 4th decade - 2 4 % , 7th decade -24%). In the third decade D of BA was 3.40_+0.64 mm, DC was 23.3_+8.8 10- 3/"kPa, CC was 0.21 _+0.09 mmZ/kPa. With ageing there was a small decrease in DC (7th decade - 9 % ) and an increase in D and CC (7th decade: D + 23%; CC + 38%) of BA. Conclusion: With age the diameter of all large arteries increases. DC and CC of the CCA decrease gradually, while DC and CC of the FA also decrease with age, but this decrease occurs mainly in the 4th decade. In contrast, the CC of the bA increases with age, due to an increase in diameter with only a minor decrease in DC. This apparently paradoxical increase of CC of the BA might be a compensation for the loss of CC in other large arteries.
96. Influence of insulin resistance on vessel wall properties of large arteries. J.J. Spek, J.A. Staessen t, A.P.G. Hoeks 2, H.A.J. Struijker Boudier, L.M.A.B. van Bortel. Departments" of Pharmacology and 2 Biophysics, Cardiovascular Research Institute, University of Limburg, Maastricht, Netherlands; i Hypertension Unit, University of Leuven. Leuven, Belgium. Insulin resistance increases the risk of cardiovascular disease.
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In addition, a relation between impaired large artery properties and cardiovascular disease has been suggested. This study investigates the influence of insulin resistance on wall properties--compliance (CC) and distensibility ( D C ) - - o f the elastic aorta and common carotid artery (CCA) and muscular brachial (BA) and femoral (FA) arteries. Insulin resistance index (IRI) was defined as [Fasting Insulin]/22.5 × e -In[Fasting Glucose] (Matthews). Fortyfour subjects with high IRI (HIRI) (male/female: 23/21, 49_+ 2 yr, body mass index (BMI) 27.3+0.5 k g / m 2, mean arterial pressure (MAP) 89_+i mmHg) were matched for gender, age, MAP and BMI with 45 subjects with a low IRI (LIRI) (male/female: 24/21, 50_+1 yr, BMI 26.6-+0.5 k g / m 2, MAP 89_+ 1 mmHg). All subjects had a fasting glucose < 6.5 mmol/l. In these subjects diameter (D) and change in D during the heart cycle were measured non-invasively with a vessel wall movement detector system. From these data and the pulse pressure (Ap; Dinamap) DC and CC were calculated. In addition, aortic pulse wave velocity (PWV)--a measure of aortic distensibility--was calculated. Data are mean _+SEM. Insulin resistance index in HIRI was 3.41 _+0.18, compared to 1.20_+0.04 in LIRI (P <0.01). HIRI and LIRI did not differ for Ap and heart rate. D of CCA, FA and BA did not differ between the two groups. DC of FA was smaller (P < 0.05) in HIRI (7.6-+0.6 10-3/kPa) than in LIRI (9.5_+0.6 10-3/kPa). CC of FA was also lower ( P <0.01) in HIRI than in LIRI (0.49_+0.03 mm2/kPa, 0.66-+0.04 mm2/kPa, resp.). There was no difference in DC and CC of CCA and BA between HIRI and LIRI. Aortic PWV was also similar in both groups. Conclusion: In insulin-resistant subjects the femoral artery is less elastic (DC), which also results in a lower compliance. Since there evidence is of a relation between insulin resistance and arterial disease, this lower distensibility of the femoral artery might be an early stage or marker of a higher risk of arterial disease.
97. Disparate effects of vasoactive drugs on large artery compliance. M.J.F. Starmans-Kool 1.3 F.A.T. Lustermans l, J.G.S. Breed 2, j.j. Spek 3, L.M.A.B. Van Bortel 3. Departments of Internal Medicine, j De Weverziekenhuis, Heerlen and 2 St Jansgas'thuis, Weert and 3 Department of Pharmacology, University of Limburg, Maastricht. Netherlands. Distensibility (DC) and compliance (CC) are important vessel wall properties. CC is related to DC and diameter (D). DC is related to elastic properties of the arterial wall; CC reflects its buffering function. DC is considered a determinant of the stress on the vessel wall. A decreased DC might lead to arterial wall damage, an important feature in atherosclerotic disease. Local DC and CC of various large arteries can be measured non-invasively with echo-tracking techniques. The present study compares the results on local DC and CC of 2 different controlled studies, one (n = 22) investigating the effect of the nitrate compound ISDN 20 mg t.i.d., the other ( n = 18) investigating the effect of the ACE inhibitor, perindopril (P) 4 mg o.d. Data are percentual change from baseline. With P DC and CC of the elastic common carotid artery (CCA) increased (18 and 8%, resp.), while D decreased (2%). At the muscular common femoral artery (CFA) P increased both DC and CC by 43%, without changing D. With ISDN, CC of
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Abstracts~Netherlands Journal of Medicine 48 (1996) A51-AIO0
the CCA increased (17%), DC did not change and D increased (11%). At the FA ISDN had no effect on CC and DC while D increased by 3%. These results show that P increases CC by increasing DC, while D is unchanged or even slightly decreased. In contrast, ISDN increases CC by increasing D without changing DC. This indicates that an increase in CC does not automatically imply an increase in DC (elasticity). The effect of P on CC was much larger at the FA than at the CCA. In contrast, with ISDN CC was increased only at the CCA and not at the FA. This indicates that the effect of drugs on vessel wall properties might depend on the vascular territory. Conclusion: These distinctive effects of vasoactive drugs on large artery DC and CC and on vascular territories may be relevant to pharmacological prevention and management of arterial disease.
98. Classicifaction as (non-)dipper is strongly determined by different definitions for day and night period. M.S. van der Steen, S.J. Graafsma 1, j. den Arend, J.W.M. Lenders, Th. Thien.
Department of Medicine, Division of General Internal Medicine, University Hospital, Nijmegen and I Department of Internal Medicine, Maria Ziekenhuis, Tilburg, Netherlands'. Ambulatory blood pressure monitoring (ABPM) is increasingly used for the diagnostic work-up in hypertensives. In several studies the significance of being a non-dipper (no or a small BP decline during the nigh0 has been emphasized to be a sign of secondary hypertension, of the presence of target organ damage etc. In a recent paper (J Hypertens 1995;13:1053-1058) it was demonstrated that the percentage of (non-)dippers was dependent on the precise definitions of the day and night period. Aim: To look for the day-night differences according to 16 of the 17 definitions in the literature. Subjects~Methods: 24-h ABPM was applied in 80 hypertensives, in 60 using the Oxford Medilog (OM) device; in the remainder the Spacelab 90207 (Sp) was used. All hypertensives were untreated for at least 2 weeks. From 09.00 to 24.00 h BP (mmHg) and heart rate (HR) in beats per min were measured every 15 rain. From 24.00 to 07.00 h every 40 rain a reading was programmed. At least 80% of all the readings had to be evaluable and prospective criteria were defined. All hypertensives had undergone two 24-h ABPM's. From all registrations the mean day and night BP and HR were calculated. Results: Mean 24-h BP and HR in the OM group was 137/87 (SD + 9 / 7 ) and 79 5=6, respectively. The corresponding Sp values were 147/95 (5= 10/8) and 77+5. According to the 16 definitions the mean difference in the OM group amounted to 16.8 + 2.7 (range 12-20) on the first and 17.2+2.5 (13-20) on the second day for systolic and for diastolic 13.1 5= 1.8 (10-15) and 12.9+2.0 (10-15) on the first and second day. HR day-night differences were 12.2± 1.1 (11-14) and 13.3+_1.1 (12-15). In the Sp group the numbers were for systolic 17.8 +_2.9 (13-23) and 18.8 + 2.9 (14-23) and for diastolic 15.8+2.1 (13-19)and 16.1 +-2.1 (1319). HR numbers were 9.9+- 1.0 (9-12) and 11.9+_ 1.1 (10-14). Conclusions: The day-night BP and HR differences and thus the percentage (non-)dippers depend on the definitions of the time-periods. In general, in accordance with the literature the difference is small when possibly awake BP's are considered as
sleep BP's and the differences are more pronounced when the definition of the night period is as short as possible (and sometimes questionable values between 22.00 and 0t.00 h are left out). It is clear that a consensus is needed for an adequate definition before (patho)physiological conclusions can be drawn.
99. Increased forearm blood flow in uncomplicated IDDM: no evidence for increased NO synthesis. G. Vervoort, J. Wetzels, J. Lutterman, J. Berden, P. Smits. Departments of Medicine and Pharmacology, University Hospital St. Radboud, Nijmegen, Netherlands'. Objective: There is considerable evidence that diabetic microangiopathy is preceded by a state of generalized capillary hyperperfusion. These observations have led to the hypothesis that changes in regional haemodynamics contribute to microvascular complications in IDDM. The cause of these early functional changes is not understood. Nitric oxide (NO) is a potent vasodilator and increases blood flow as well as capillary permeability. Therefore NO is a candidate for mediating increases in blood flow and vascular permeability induced by diabetes. We performed a study in which we investigated basal forearm blood flow and NO synthesis in uncomplicated type 1 diabetic patients (DP). Design~Methods: We studied 46 normal controls (C) and 34 normoalbuminuric DP. Forearm blood flow (FBF) was measured using plethysmography during brachial artery infusion of saline followed by infusion of N%monomethyl-L-arginine (t.-NMMA), an inhibitor of endothelial NO synthesis and noradrenaline (NA), an endothelium-independent vasoconstrictor. All subjects were in a fasting state and glucose was not corrected to avoid confounding by the vasodilator effect of insulin. Data were analyzed by repeated measures of ANOVA or unpaired t-test if indicated. Results were expressed as mean _+SEM. Results: Basal FBF was significantly increased in DP compared to C (2.8+0.2 and 2.0+0.1 m l / m i n / d l ) , P < 0 . 0 1 . t.NMMA caused similar vasocontriction in DP as in C (30.2+ 2.0 and 31.0+2.3%). The dose-response curve corrected for flow (concentration-response curve) was identical in both groups. The vasocontricting effect of NA was not different in both groups (43.9 _ 3.0 and 40.0 _ 3.2%). Conclusion: Basal (forearm) blood flow is increased in uncomplicated type 1 diabetes mellitus. There is however no evidence that basal endothelial nitric oxide synthesis is increased. Other vasodilating factors may therefore contribute to capillary hyperperfusion.
100. Circadian blood pressure regulation during long-term head-down tilted bedrest. A.J. Voogel, W.J. Stok, G.A. van Montfrans, G.J. Langewouters 2, J.M. Karemaker. Departments of Internal Medicine and l Physiology, University of Amsterdam, TNO BioMedical Instrumentation, Amsterdam, Netherlands. Objective: Head-down tilted bedrest (HDT) is used as a ground-based microgravity simulation model. In HDT the influence of two major determinants of the circadian blood pressure profile--activity and posture--are reduced. Therefore, HDT allows us to study the intrinsic regulatory mechanisms responsible
95. Effects of ageing on wall properties of different large arteries. J.J. Spek, J.A. Staessen t, A.P.G. Hoeks 2, H.A.J. Struijker Boudier, L.M.A.B. Van Bortel. Departments of Pharmacology and 2 Biophysics, Cardiovascular Research Institute, University of Limburg, Maastricht, Netherlands. 1Hypertension Unit, University of Leuven. Leuven, Belgium. Compliance (CC) and distensibility (DC) are vessel wall properties of large arteries. It is thought that impaired large artery properties are related to an increased cardiovascular risk. This study investigates the influence of age on the wall properties of the elastic common carotid artery (CCA) and the muscular brachial (BA) and femoral (FA) arteries. 175 persons, who did not use vasoactive mediation, were divided into 5 age-decades (20-29 yr up to 60-69 yr). In these subjects diameter (D) and change in D during the heart cycle were measured non-invasively with a vessel wall movement detector system. From these data and pulse pressure (Ap; Dinamap) DC and CC were calculated. Data are mean-+ SD. Mean arterial pressure was 82 4-1 mmHg in the 3rd decade and 86 4- 1 mmHg in the 7th decade. In the 3rd decade D of CCA was 6.30 -+0.70 mm, DC was 32.3 _+8.1 I0- 3/kPa, CC was 1.02_+0.36 mm2/kPa. With ageing there was a gradual increase in D (7th decade: +21%) and decrease in DC and CC (7th decade: DC - 5 1 % ; CC - 2 9 % ) of CCA. D of FA was 8.47_+ 1.33 mm in the 3rd decade. DC was 15.3_+5.8 10-3/kPa, CC was 0.83_+0.30 mm2/kPa. Ageing resulted also in an increase in D, which mainly occurred in the 5th decade (5th decade + 11%, 7th decade + 15%). There was also a decrease in DC and CC of FA, mainly in the 4th decade (DC 4th decade - 28%, 7th decade - 4 5 % ; CC 4th decade - 2 4 % , 7th decade -24%). In the third decade D of BA was 3.40_+0.64 mm, DC was 23.3_+8.8 10- 3/"kPa, CC was 0.21 _+0.09 mmZ/kPa. With ageing there was a small decrease in DC (7th decade - 9 % ) and an increase in D and CC (7th decade: D + 23%; CC + 38%) of BA. Conclusion: With age the diameter of all large arteries increases. DC and CC of the CCA decrease gradually, while DC and CC of the FA also decrease with age, but this decrease occurs mainly in the 4th decade. In contrast, the CC of the bA increases with age, due to an increase in diameter with only a minor decrease in DC. This apparently paradoxical increase of CC of the BA might be a compensation for the loss of CC in other large arteries.
96. Influence of insulin resistance on vessel wall properties of large arteries. J.J. Spek, J.A. Staessen t, A.P.G. Hoeks 2, H.A.J. Struijker Boudier, L.M.A.B. van Bortel. Departments" of Pharmacology and 2 Biophysics, Cardiovascular Research Institute, University of Limburg, Maastricht, Netherlands; i Hypertension Unit, University of Leuven. Leuven, Belgium. Insulin resistance increases the risk of cardiovascular disease.
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In addition, a relation between impaired large artery properties and cardiovascular disease has been suggested. This study investigates the influence of insulin resistance on wall properties--compliance (CC) and distensibility ( D C ) - - o f the elastic aorta and common carotid artery (CCA) and muscular brachial (BA) and femoral (FA) arteries. Insulin resistance index (IRI) was defined as [Fasting Insulin]/22.5 × e -In[Fasting Glucose] (Matthews). Fortyfour subjects with high IRI (HIRI) (male/female: 23/21, 49_+ 2 yr, body mass index (BMI) 27.3+0.5 k g / m 2, mean arterial pressure (MAP) 89_+i mmHg) were matched for gender, age, MAP and BMI with 45 subjects with a low IRI (LIRI) (male/female: 24/21, 50_+1 yr, BMI 26.6-+0.5 k g / m 2, MAP 89_+ 1 mmHg). All subjects had a fasting glucose < 6.5 mmol/l. In these subjects diameter (D) and change in D during the heart cycle were measured non-invasively with a vessel wall movement detector system. From these data and the pulse pressure (Ap; Dinamap) DC and CC were calculated. In addition, aortic pulse wave velocity (PWV)--a measure of aortic distensibility--was calculated. Data are mean _+SEM. Insulin resistance index in HIRI was 3.41 _+0.18, compared to 1.20_+0.04 in LIRI (P <0.01). HIRI and LIRI did not differ for Ap and heart rate. D of CCA, FA and BA did not differ between the two groups. DC of FA was smaller (P < 0.05) in HIRI (7.6-+0.6 10-3/kPa) than in LIRI (9.5_+0.6 10-3/kPa). CC of FA was also lower ( P <0.01) in HIRI than in LIRI (0.49_+0.03 mm2/kPa, 0.66-+0.04 mm2/kPa, resp.). There was no difference in DC and CC of CCA and BA between HIRI and LIRI. Aortic PWV was also similar in both groups. Conclusion: In insulin-resistant subjects the femoral artery is less elastic (DC), which also results in a lower compliance. Since there evidence is of a relation between insulin resistance and arterial disease, this lower distensibility of the femoral artery might be an early stage or marker of a higher risk of arterial disease.
97. Disparate effects of vasoactive drugs on large artery compliance. M.J.F. Starmans-Kool 1.3 F.A.T. Lustermans l, J.G.S. Breed 2, j.j. Spek 3, L.M.A.B. Van Bortel 3. Departments of Internal Medicine, j De Weverziekenhuis, Heerlen and 2 St Jansgas'thuis, Weert and 3 Department of Pharmacology, University of Limburg, Maastricht. Netherlands. Distensibility (DC) and compliance (CC) are important vessel wall properties. CC is related to DC and diameter (D). DC is related to elastic properties of the arterial wall; CC reflects its buffering function. DC is considered a determinant of the stress on the vessel wall. A decreased DC might lead to arterial wall damage, an important feature in atherosclerotic disease. Local DC and CC of various large arteries can be measured non-invasively with echo-tracking techniques. The present study compares the results on local DC and CC of 2 different controlled studies, one (n = 22) investigating the effect of the nitrate compound ISDN 20 mg t.i.d., the other ( n = 18) investigating the effect of the ACE inhibitor, perindopril (P) 4 mg o.d. Data are percentual change from baseline. With P DC and CC of the elastic common carotid artery (CCA) increased (18 and 8%, resp.), while D decreased (2%). At the muscular common femoral artery (CFA) P increased both DC and CC by 43%, without changing D. With ISDN, CC of
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Abstracts~Netherlands Journal of Medicine 48 (1996) A51-AIO0
the CCA increased (17%), DC did not change and D increased (11%). At the FA ISDN had no effect on CC and DC while D increased by 3%. These results show that P increases CC by increasing DC, while D is unchanged or even slightly decreased. In contrast, ISDN increases CC by increasing D without changing DC. This indicates that an increase in CC does not automatically imply an increase in DC (elasticity). The effect of P on CC was much larger at the FA than at the CCA. In contrast, with ISDN CC was increased only at the CCA and not at the FA. This indicates that the effect of drugs on vessel wall properties might depend on the vascular territory. Conclusion: These distinctive effects of vasoactive drugs on large artery DC and CC and on vascular territories may be relevant to pharmacological prevention and management of arterial disease.
98. Classicifaction as (non-)dipper is strongly determined by different definitions for day and night period. M.S. van der Steen, S.J. Graafsma 1, j. den Arend, J.W.M. Lenders, Th. Thien.
Department of Medicine, Division of General Internal Medicine, University Hospital, Nijmegen and I Department of Internal Medicine, Maria Ziekenhuis, Tilburg, Netherlands'. Ambulatory blood pressure monitoring (ABPM) is increasingly used for the diagnostic work-up in hypertensives. In several studies the significance of being a non-dipper (no or a small BP decline during the nigh0 has been emphasized to be a sign of secondary hypertension, of the presence of target organ damage etc. In a recent paper (J Hypertens 1995;13:1053-1058) it was demonstrated that the percentage of (non-)dippers was dependent on the precise definitions of the day and night period. Aim: To look for the day-night differences according to 16 of the 17 definitions in the literature. Subjects~Methods: 24-h ABPM was applied in 80 hypertensives, in 60 using the Oxford Medilog (OM) device; in the remainder the Spacelab 90207 (Sp) was used. All hypertensives were untreated for at least 2 weeks. From 09.00 to 24.00 h BP (mmHg) and heart rate (HR) in beats per min were measured every 15 rain. From 24.00 to 07.00 h every 40 rain a reading was programmed. At least 80% of all the readings had to be evaluable and prospective criteria were defined. All hypertensives had undergone two 24-h ABPM's. From all registrations the mean day and night BP and HR were calculated. Results: Mean 24-h BP and HR in the OM group was 137/87 (SD + 9 / 7 ) and 79 5=6, respectively. The corresponding Sp values were 147/95 (5= 10/8) and 77+5. According to the 16 definitions the mean difference in the OM group amounted to 16.8 + 2.7 (range 12-20) on the first and 17.2+2.5 (13-20) on the second day for systolic and for diastolic 13.1 5= 1.8 (10-15) and 12.9+2.0 (10-15) on the first and second day. HR day-night differences were 12.2± 1.1 (11-14) and 13.3+_1.1 (12-15). In the Sp group the numbers were for systolic 17.8 +_2.9 (13-23) and 18.8 + 2.9 (14-23) and for diastolic 15.8+2.1 (13-19)and 16.1 +-2.1 (1319). HR numbers were 9.9+- 1.0 (9-12) and 11.9+_ 1.1 (10-14). Conclusions: The day-night BP and HR differences and thus the percentage (non-)dippers depend on the definitions of the time-periods. In general, in accordance with the literature the difference is small when possibly awake BP's are considered as
sleep BP's and the differences are more pronounced when the definition of the night period is as short as possible (and sometimes questionable values between 22.00 and 0t.00 h are left out). It is clear that a consensus is needed for an adequate definition before (patho)physiological conclusions can be drawn.
99. Increased forearm blood flow in uncomplicated IDDM: no evidence for increased NO synthesis. G. Vervoort, J. Wetzels, J. Lutterman, J. Berden, P. Smits. Departments of Medicine and Pharmacology, University Hospital St. Radboud, Nijmegen, Netherlands'. Objective: There is considerable evidence that diabetic microangiopathy is preceded by a state of generalized capillary hyperperfusion. These observations have led to the hypothesis that changes in regional haemodynamics contribute to microvascular complications in IDDM. The cause of these early functional changes is not understood. Nitric oxide (NO) is a potent vasodilator and increases blood flow as well as capillary permeability. Therefore NO is a candidate for mediating increases in blood flow and vascular permeability induced by diabetes. We performed a study in which we investigated basal forearm blood flow and NO synthesis in uncomplicated type 1 diabetic patients (DP). Design~Methods: We studied 46 normal controls (C) and 34 normoalbuminuric DP. Forearm blood flow (FBF) was measured using plethysmography during brachial artery infusion of saline followed by infusion of N%monomethyl-L-arginine (t.-NMMA), an inhibitor of endothelial NO synthesis and noradrenaline (NA), an endothelium-independent vasoconstrictor. All subjects were in a fasting state and glucose was not corrected to avoid confounding by the vasodilator effect of insulin. Data were analyzed by repeated measures of ANOVA or unpaired t-test if indicated. Results were expressed as mean _+SEM. Results: Basal FBF was significantly increased in DP compared to C (2.8+0.2 and 2.0+0.1 m l / m i n / d l ) , P < 0 . 0 1 . t.NMMA caused similar vasocontriction in DP as in C (30.2+ 2.0 and 31.0+2.3%). The dose-response curve corrected for flow (concentration-response curve) was identical in both groups. The vasocontricting effect of NA was not different in both groups (43.9 _ 3.0 and 40.0 _ 3.2%). Conclusion: Basal (forearm) blood flow is increased in uncomplicated type 1 diabetes mellitus. There is however no evidence that basal endothelial nitric oxide synthesis is increased. Other vasodilating factors may therefore contribute to capillary hyperperfusion.
100. Circadian blood pressure regulation during long-term head-down tilted bedrest. A.J. Voogel, W.J. Stok, G.A. van Montfrans, G.J. Langewouters 2, J.M. Karemaker. Departments of Internal Medicine and l Physiology, University of Amsterdam, TNO BioMedical Instrumentation, Amsterdam, Netherlands. Objective: Head-down tilted bedrest (HDT) is used as a ground-based microgravity simulation model. In HDT the influence of two major determinants of the circadian blood pressure profile--activity and posture--are reduced. Therefore, HDT allows us to study the intrinsic regulatory mechanisms responsible