The effect of purinergic P2 receptor blockade on skeletal muscle exercise hyperemia in miniature swine.

PURPOSE: ATP could play an important role in skeletal muscle blood flow regulation by inducing vasodilation via purinergic P2 receptors. This study investigated the role of P2 receptors in exercise hyperemia in miniature swine. METHODS: We measured regional blood flow with radiolabeled-microsphere technique and systemic hemodynamics before and after arterial infusion of the P2 receptor antagonist reactive blue 2 during treadmill exercise (5.2 km/h, ~60 % VO2max) and arterial ATP infusion in female Yucatan miniature swine (~29 kg). RESULTS: Mean blood flow during exercise from the 16 sampled skeletal muscle tissues was 138 ± 18 mL/min/100 g (mean ± SEM), and it was reduced in 11 (~25 %) of the 16 sampled skeletal muscles after RB2 was infused. RB2 also lowered diaphragm blood flow and kidney blood flow, whereas lung tissue blood flow was increased (all P < 0.05). Infusion of RB2 increased arterial lactate concentration during exercise from 1.6 ± 0.5 to 3.4 ± 0.6 mmol/L and heart rate from 216 ± 12 to 230 ± 9 beats/min, whereas blood pressure was unaltered. Arterial ATP infusion caused a ~twofold increase in blood flow in 15 of the 16 sampled muscle tissues and this effect was abolished after RB2 infusion. CONCLUSIONS: These results indicate that P2 receptors play a role in regulating skeletal muscle blood flow during exercise in miniature swine.

Upregulation of cyclooxygenase-2 expression in porcine macula densa with chronic nitric oxide synthase inhibition.

The objective of this study was to investigate the effects of chronic inhibition of nitric oxide synthase (NOS) on cyclooxygenase-2 (COX-2) expression in the macula densa (MD) of swine, as well as the effects on expression of related proteins. Adult female Yucatan swine were given either tap water (control, n = 6) or water with N (G)-nitro-L-arginine methyl ester (L-NAME, 100 mg/liter, n = 5) for a minimum of 30 days. Duplicate samples of kidney were fixed or snap frozen. There was a significant (P = .0082) upregulation of COX-2 mRNA expression in the MD of L-NAME, as well as an apparent increase in COX-2 protein. Plasma renin activity also increased with L-NAME treatment (control, 0.34 ± 0.08 ng/ml; L-NAME, 1.26 ± 0.03 ng/ml; P = .00000003). There were no differences between groups in expression of either inducible NOS or renin protein or in serum electrolyte concentrations. In conclusion, with chronic inhibition of NOS, COX-2 in MD is upregulated, perhaps to compensate for loss of nitric oxide. Increases in COX-2 products may counteract renal arteriolar constriction and sustain renin release.

Effects of chronic nitric oxide synthase inhibition on endothelium-dependent and -independent relaxation in arteries that perfuse skeletal muscle of swine.

The purpose of this investigation was to test the hypothesis that chronic N(G)-nitro-l-arginine methyl ester (l-NAME) treatment produces differential effects on conduit artery and resistance arteriole relaxation responses to endothelium-dependent and -independent vasodilators in arteries that perfuse skeletal muscle of swine. To test this hypothesis, conduit skeletal muscle arteries and second-order skeletal muscle (2A) arterioles were harvested from 14 Yucatan swine that were chronically administered l-NAME and from 16 controls. In vitro assessments of vasorelaxation to increasing doses of acetylcholine (ACH), bradykinin (BK), and sodium nitroprusside (SNP) were performed in both conduit and 2A arterioles. l-NAME treatment produced a significant reduction in both BK and ACH relaxation responses in the conduit arteries. In contrast, the relaxation response and/or sensitivity to SNP were significantly greater in the intact, but not denuded, conduit arterial rings from chronically l-NAME-treated swine. There were no significant effects of chronic l-NAME treatment on vasodilation of skeletal muscle arterioles. These findings suggest (1) that unlike arterioles, skeletal muscle conduit arteries do not functionally compensate for a lack of NO through the upregulation of alternative vasodilator pathways; (2) that the greater relaxation response in conduit arteries of chronically l-NAME-treated swine to SNP can be explained by alterations to the endothelium.

Production of endothelial nitric oxide synthase (eNOS) over-expressing piglets.

Vascular function, vascular structure, and homeostasis are thought to be regulated in part by nitric oxide (NO) released by endothelial cell nitric oxide synthase (eNOS), and NO released by eNOS plays an important role in modulating metabolism of skeletal and cardiac muscle in health and disease. The pig is an optimal model for human diseases because of the large number of important similarities between the genomic, metabolic and cardiovascular systems of pigs and humans. To gain a better understanding of cardiovascular regulation by eNOS we produced pigs carrying an endogenous eNOS gene driven by a Tie-2 promoter and tagged with a V5 His tag. Nuclear transfer was conducted to create these animals and the effects of two different oocyte activation treatments and two different culture systems were examined. Donor cells were electrically fused to the recipient oocytes. Electrical fusion/activation (1 mM calcium in mannitol: Treatment 1) and electrical fusion (0.1 mM calcium in mannitol)/chemical activation (200 microM Thimerosal for 10 min followed by 8 mM DTT for 30 min: Treatment 2) were used. Embryos were surgically transferred to the oviducts of gilts that exhibited estrus on the day of fusion or the day of transfer. Two cloned transgenic piglets were born from Treatment 1 and low oxygen, and another two from Treatment 2 and normal oxygen. PCR, RT-PCR, Western blotting and immunohistochemistry confirmed that the pigs were transgenic, made message, made the fusion protein and that the fusion protein localized to the endothelial cells of placental vasculature from the conceptuses as did the endogenous eNOS. Thus both activation conditions and culture systems are compatible with development to term. These pigs will serve as the founders for a colony of miniature pigs that will help to elucidate the function of eNOS in regulating muscle metabolism and the cardiorespiratory system.

Thyroid status and nitric oxide in rat arterial vessels.

Thyroid disease has profound effects on cardiovascular function. Hypo- and hyperthyroidism, for example, are associated with reduced and increased maximal endothelium-dependent vasodilation respectively. We therefore hypothesized that the capacity for vascular nitric oxide (NO) formation is decreased in hypothyroidism and increased in hyperthyroidism. To test this hypothesis, rats were made hypothyroid (HYPO) with propylthiouracil or hyperthyroid (HYPER) with triiodothyronine over 3-4 months. Compared with euthyroid control rats (EUT), HYPO exhibited blunted growth and lower citrate synthase activity in the soleus muscle; HYPER exhibited left ventricular hypertrophy and higher citrate synthase activity in the soleus muscle (P<0.05 for all effects). The capacity for NO formation was determined in aortic extracts by formation of [3H]L-citrulline from [3H]L-arginine, i.e. NO synthase (NOS) activity. Thyroid status modulated NOS activity (EUT, 36.8 +/- 5.5 fmol/h per mg protein; HYPO, 26.0 +/- 7.9; HYPER, 64.6 +/- 12.7; P<0.05, HYPER vs HYPO). Expression of endothelial and neural isoforms of NOS was modulated by thyroid status in a parallel fashion. Capacity for responding to NO was also determined via measuring cGMP concentration in aortae incubated with sodium nitroprusside. Stimulated cGMP formation was also modulated by thyroid status (EUT, 73.0 +/- 20.2 pmol/mg protein; HYPO, 152.4 +/- 48.7; HYPER, 10.4 +/- 2.6; P<0.05, HYPER vs HYPO). These data indicate that thyroid status alters capacities for both formation of and responding to NO. The former finding may contribute to previous findings concerning vascular function in thyroid disease states.

Thyroid status and endothelium-dependent vasodilation in skeletal muscle.

Cardiovascular dysfunction is characteristic of both hypo- and hyperthyroidism. Endothelium-dependent dilation of conductance vessels is impaired in hypothyroidism but augmented in hyperthyroidism. We hypothesized that these alterations in dilation extend into the resistance vasculature of skeletal muscle. To test this hypothesis, rats were made hypothyroid with propylthiouracil (Hypo; n = 13) or hyperthyroid with triiodothyronine (Hyper; n = 9) over 3-4 mo. Compared with euthyroid controls (Eut; n = 14), Hypo rats were characterized by reduced skeletal muscle oxidative capacity and blunted growth; Hyper rats exhibited increased muscle oxidative capacity and left ventricular hypertrophy (P < 0.05 for all effects). Vasodilation to the endothelium-dependent agent acetylcholine ( approximately 2 x 10(-4) M) in skeletal muscle was determined in situ. Conductance in certain muscles increased from control [e.g., soleus: 0.98 +/- 0.15 (Eut), 0.79 +/- 0.14 (Hypo), and 1.06 +/- 0.24 ml.min(-1).100 g(-1).mmHg(-1) (Hyper); not significant among groups] to acetylcholine [1.91 +/- 0.21 (Eut), 2.28 +/- 0.26 (Hypo), and 2.15 +/- 0.33 ml.min(-1).100 g(-1).mmHg(-1) (Hyper); P < 0.05 vs. control values for all groups] but did not differ among groups. Expression of mRNA for the endothelial isoform of nitric oxide synthase in resistance vessels isolated from various muscles was similarly unchanged with alterations in thyroid status [e.g., soleus 1A arterioles: 33.15 +/- 0.58 (Eut), 32.73 +/- 0.27 (Hypo), and 32.80 +/- 0.54 (Hyper) cycles at threshold; not significant]. These data suggest that endothelium-dependent dilation of resistance vasculature in skeletal muscle is unchanged in both hypo- and hyperthyroidism. These data also emphasize the importance of examining resistance vasculature to improve understanding of effects of chronic disease on integrated cardiovascular function.

Nonuniform effects of endurance exercise training on vasodilation in rat skeletal muscle.

Endurance exercise training (Ex) has been shown to increase maximal skeletal muscle blood flow. The purpose of this study was to test the hypothesis that increased endothelium-dependent vasodilation is associated with the Ex-induced increase in muscle blood flow. Furthermore, we hypothesized that enhanced endothelium-dependent dilation is confined to vessels in high-oxidative muscles that are recruited during Ex. To test these hypotheses, sedentary (Sed) and rats that underwent Ex (30 m/min x 10% grade, 60 min/day, 5 days/wk, 8-12 wk) were studied using three experimental approaches. Training effectiveness was evidenced by increased citrate synthase activity in soleus and vastus lateralis (red section) muscles (P < 0.05). Vasodilatory responses to the endothelium-dependent agent acetylcholine (ACh) in situ tended to be augmented by training in the red section of gastrocnemius muscle (RG; Sed: control, 0.69 +/- 0.12; ACh, 1.25 +/- 0.15; Ex: control, 0.86 +/- 0.17; ACh, 1.76 +/- 0.27 ml x min(-1) x 100 g(-1) x mmHg(-1); 0.05 < P < 0.10 for Ex vs. Sed during ACh). Responses to ACh in situ did not differ between Sed and Ex for either the soleus muscle or white section of gastrocnemius muscle (WG). Dilatory responses of second-order arterioles from the RG in vitro to flow (4-8 microl/min) and sodium nitroprusside (SNP; 10(-7) through 10(-4) M), but not ACh, were augmented in Ex (vs. Sed; P < 0.05). Dilatory responses to ACh, flow, and SNP of arterioles from soleus and WG muscles did not differ between Sed and Ex. Content of the endothelial isoform of nitric oxide synthase (eNOS) was increased in second-order, fourth-order, and fifth-order arterioles from the RG of Ex; eNOS content was similar between Sed and Ex in vessels from the soleus and WG muscles. These findings indicate that Ex induces endothelial adaptations in fast-twitch, oxidative, glycolytic skeletal muscle. These adaptations may contribute to enhanced skeletal muscle blood flow in endurance-trained individuals.

Effects of hypothyroidism on the skeletal muscle blood flow response to contractions.

Hypothyroidism is associated with impaired blood flow to skeletal muscle under whole body exercise conditions. It is unclear whether poor cardiac and/or vascular function account for blunted muscle blood flow. Our experiment isolated a small group of hindlimb muscles and simulated exercise via tetanic contractions. We hypothesized that muscle blood flow would be attenuated in hypothyroid rats (HYPO) compared with euthyroid rats (EUT). Rats were made hypothyroid by mixing propylthiouracil in their drinking water (2.35 x 10-3 mol/l). Treatment efficacy was evidenced by lower serum T3 concentrations and resting heart rates in HYPO (both P<0.05). In the experimental preparation, isometric contractions of the lower right hindlimb muscles at a rate of 30 tetani/min were induced via sciatic nerve stimulation. Regional blood flows were determined by the radiolabelled microsphere method at three time points: rest, 2 min of contractions and 10 min of contractions. Muscle blood flow generally increased from rest ( approximately 5-10 ml/min per 100 g) through contractions for both groups. Further, blood flow during contractions did not differ between groups for any muscle (eg. red section of gastrocnemius muscle; EUT, 59.9 +/- 14.1; HYPO, 61.1 +/- 15.0; NS between groups). These findings indicate that hypothyroidism does not significantly impair skeletal muscle blood flow when only a small muscle mass is contracting. Our findings suggest that impaired blood flow under whole body exercise is accounted for by inadequate cardiac function rather than abnormal vascular function.

Subungual melanoma in situ: two independent streaks in one nail bed.

We report an unusual case of two nail-bed streaks under one nail, revealing melanoma in situ affecting the nail bed and plate, but not the nail fold. This unusual mode of presentation together with the absence of any nail-fold involvement has not been reported previously. We highlight the need for early histological assessment of nail-bed lesions and discuss subungual melanoma.

Effects of nitric oxide synthase inhibition on vascular conductance during high speed treadmill exercise in rats.

To determine the functional role of nitric oxide (NO) in regulating vascular conductance during high intensity dynamic exercise in skeletal muscles composed of all major fibre types, female Wistar rats (277 +/- 4 g; n = 7) were run on a motor-driven treadmill at a speed and gradient (60 m min(-1), 10 % gradient) established to yield maximal oxygen uptake (V(O2,max)). Vascular conductance (ml min(-1) (100 g)(-1) mmHg(-1)), defined as blood flow normalised to mean arterial pressure (MAP), was determined using radiolabelled microspheres during exercise before and after NO synthase (NOS) inhibition with N (G)-nitro-L-arginine methyl ester (L-NAME; 10 mg kg(-1), I.A.). The administration of L-NAME increased MAP from pre-L-NAME baseline values, demonstrating that NOS activity is reduced. The administration of L-NAME also reduced vascular conductance in 20 of the 28 individual hindlimb muscles or muscle parts examined during high speed treadmill exercise. These reductions in vascular conductance correlated linearly with the estimated sum of the percentage of slow twitch oxidative (SO) and fast twitch oxidative glycolytic (FOG) types of fibres in each muscle (Deltaconductance = -0.0082(%SO + %FOG) - 0.0105; r = 0.66; P < 0.001). However, if the reduction in vascular conductance found in the individual hindquarter muscles or muscle parts was expressed as a percentage decrease from the pre-L-NAME value (%Delta = (pre-L-NAME conductance - post-L-NAME conductance)/ pre-L-NAME conductance x 100), then the reduction in vascular conductance was similar in all muscles examined (average %Delta = -23 +/- 2 %). These results suggest that NO contributes substantially to the regulation of vascular conductance within and among muscles of the rat hindquarter during high intensity exercise. When expressed in absolute terms, the results suggest that the contribution of NO to the regulation of vascular conductance during high intensity exercise is greater in muscles that possess a high oxidative capacity. In contrast, if results are expressed in relative terms, then the contribution of NO to the regulation of vascular conductance during high intensity exercise is similar across the different locomotor muscles located in the rat hindlimb and independent of the fibre type composition.

Skeletal muscle oxidative capacity and exercise tolerance in rats with heart failure.

PURPOSE: Past research has shown the development of exercise intolerance after myocardial infarction (MI). The purpose of this study was to test the hypothesis that reductions in oxidative enzyme activity, in a variety of skeletal muscles, coincide with the development of exercise intolerance in a rat model of chronic heart failure (CHF) induced by MI. METHODS: The animals were initially divided into two groups: sham-operated controls (Sham) and animals in which a MI was surgically induced. MI rats were then subdivided into two groups according to left ventricular end-diastolic pressure (LVEDP): <20 mm Hg [small MI (SMI)] and > 20 mm Hg [large MI (LMI)]. Exercise tolerance was measured by performing a progressive run to fatigue test (RTF). Citrate synthase (CS), 3-hydroxyacyl CoA dehydrogenase (HADH), and malate dehydrogenase (MDH) activities were measured in six hindlimb muscles. RESULTS: After approximately 6 wk of recovery, LVEDP differed among groups (P < 0.05): Sham (1 +/- 1 mm Hg, N = 7), SMI (7 +/- 2 mm Hg, N = 7), and LMI (30 +/- 2 mm Hg, N = 6). RTF was 20 +/- 1 min for Sham, 25 +/- 3 min for SMI, and 11 +/- 2 min for LMI (P < 0.05 for LMI vs Sham, SMI). Significant reductions in enzyme activity were found for all three enzymes in the red portion of the gastrocnemius muscles of LMI. However, no significant correlation was found between RTF and CS, HADH, or MDH in any muscle of the three groups of animals. DISCUSSION: The results of the present study demonstrate that severe left ventricular dysfunction is associated with reductions in exercise tolerance and modest decreases in oxidative enzyme activities in selected muscles. It does not appear, however, that the development of exercise intolerance in CHF and oxidative enzyme activities are mechanistically related to one another.

Thyroid status influences baroreflex function and autonomic contributions to arterial pressure and heart rate.

The effect of thyroid status on arterial baroreflex function and autonomic contributions to resting blood pressure and heart rate (HR) were evaluated in conscious rats. Rats were rendered hyperthyroid (Hyper) or hypothyroid (Hypo) with triiodothyronine and propylthiouracil treatments, respectively. Euthyroid (Eut), Hyper, and Hypo rats were chronically instrumented to measure mean arterial pressure (MAP), HR, and lumbar sympathetic nerve activity (LSNA). Baroreflex function was evaluated with the use of a logistic function that relates LSNA or HR to MAP during infusion of phenylephrine and sodium nitroprusside. Contributions of the autonomic nervous system to resting MAP and HR were assessed by blocking autonomic outflow with trimethaphan. In Hypo rats, the arterial baroreflex curve for both LSNA and HR was shifted downward. Hypo animals exhibited blunted sympathoexcitatory and tachycardic responses to decreases in MAP. Furthermore, the data suggest that in Hypo rats, the sympathetic influence on HR was predominant and the autonomic contribution to resting MAP was greater than in Eut rats. In Hyper rats, arterial baroreflex function generally was similar to that in Eut rats. The autonomic contribution to resting MAP was not different between Hyper and Eut rats, but predominant parasympathetic influence on HR was exhibited in Hyper rats. The results demonstrate baroreflex control of LSNA and HR is attenuated in Hypo but not Hyper rats. Thyroid status alters the balance of sympathetic to parasympathetic tone in the heart, and the Hypo state increases the autonomic contributions to resting blood pressure.

Interaction of gender and exercise training: vasomotor reactivity of porcine skeletal muscle arteries.

The purpose of the present study was to test the hypothesis that gender influences exercise training-induced adaptations of vascular reactivity of porcine arteries that provide blood flow to skeletal muscle and femoral and brachial arteries. Male and female Yucatan miniature swine were exercise trained on a motor-driven treadmill or cage confined for 16-20 wk. Contractile responses of arterial rings were evaluated in vitro by determining concentration-response curves for endothelin-1 (ET-1; 10(-10) to 10(-7) M) and norepinephrine (NE; 10(-10) to 10(-4) M). Relaxation responses of arteries precontracted with 30 microM PGF(2alpha) were examined for endothelium-dependent agents [bradykinin (BK; 10(-11) to 10(-6) M), ACh (10(-10) to 10(-4) M), and a Ca(2+) ionophore, A-23187 (10(-6) M)] and a endothelium-independent agent [sodium nitroprusside (10(-10) to 10(-4) M)]. Arteries from female pigs developed greater contractile force in response to ET-1 than arteries from male pigs, whereas contractile responses to NE and KCl were similar in arteries from both genders. Femoral arteries from females exhibited greater endothelium-mediated vasorelaxation (BK and ACh) than did those from males. In contrast, brachial arteries of males were more responsive to BK and ACh than brachial arteries of females. Exercise training increased ET-1-induced contractions in arteries from males (without endothelium) but not in arteries from females. Training had no effect on endothelium-dependent relaxation in arteries from males but increased relaxation responses in brachial arteries from females. We conclude that both gender and anatomic origin of the artery influence exercise training-induced adaptations of vascular reactivity of porcine skeletal muscle conduit arteries.

Thyroid status and response to endothelin-1 in rat arterial vessels.

We have previously reported that changes in thyroid status are associated with significant alterations in skeletal muscle blood flow during exercise and that changes in endothelium-dependent vasodilation may contribute to these blood flow abnormalities. The purpose of this study was to test the hypothesis that altered endothelium-dependent vasoconstriction is also associated with changes in thyroid status. To test this hypothesis, rats were rendered hypothyroid with propylthiouracil (Hypo, n = 14) or hyperthyroid with triiodothyronine (Hyper, n = 14) over approximately 3 mo. Treatment efficacy was confirmed by altered (P < 0.05) citrate synthase activity in several hindlimb skeletal muscles from Hypo and Hyper, compared with that in muscles from euthyroid rats (Eut, n = 12). Vascular rings were prepared from abdominal aortae, and responses to several vasoactive agents were determined in vitro. As found previously, maximal acetylcholine-induced vasorelaxation was modulated by thyroid status (Eut, 47 +/- 9; Hypo, 28 +/- 6; Hyper, 68 +/- 5%; P < 0.05). Contractile responses of vascular rings with intact endothelium to the endothelium-derived constrictor endothelin-1 (ET-1), however, were similar among groups across a range of ET-1 concentrations. In addition, maximal responses [Eut, 3.75 +/- 0.47; Hypo, 2.72 +/- 0.25; Hyper, 3.22 +/- 0.42 g; not significant (NS)] and sensitivities (Eut, 8.12 +/- 0.09; Hypo, 8.10 +/- 0.06; Hyper, 8.28 +/- 0.09 -log M; NS) to ET-1 were similar among groups. If these findings from the conduit-type abdominal aorta extend into resistance vasculature, it appears that changes in endothelium-dependent vasoconstriction do not contribute to skeletal muscle blood flow abnormalities associated with thyroid disease states.

Acetylcholine is a vasodilator of porcine skeletal muscle arteries.

The purpose of this study was to test the hypothesis that porcine skeletal muscle arteries exhibit concentration-dependent vasodilation in response to acetylcholine (ACH) as observed in other mammals. We conducted three experiments. First, vasorelaxation responses to ACH were examined in isolated segments of femoral and brachial arteries, mounted on myographs and studied in vitro. Second, we determined whether resistance arteries from porcine skeletal muscle exhibit vasodilation in response to ACH by isolating second order arterioles (2-A) from the medial (MHT), deep-long (LOH) and lateral (LAT) heads of the triceps brachii muscles of four pigs. The rationale for selection of arterioles from these muscles was that these muscles represent muscles composed primarily of slow-oxidative, fast-oxidative-glycolytic, and fast-glycolytic muscle fiber types, respectively. 2-As were isolated and cannulated with micropipettes and intraluminal pressure set at 60 cm H2O. In both sets of in vitro experiments, we determined responses to an endothelium-independent dilator, sodium nitroprusside (10(-10)-10(-4) M), and to endothelium-dependent agents ACH (10(-10)-10(-4) M), and bradykinin (BK; 10(-11)-10(-6) M). Third, we used transcutaneous ultrasound imaging to measure changes in artery diameters and Doppler-principle measurements of blood flow velocities to estimate changes in total blood flow in the femoral vascular bed. Results reveal that ACH and BK produced similar vasorelaxation responses in femoral and brachial arteries and vasodilation of skeletal muscle 2-As. Also, ACH produced increases in blood flow and decreases in vascular resistance in the femoral vascular bed. These results indicate that the arterial tree of porcine skeletal muscle exhibits ACH-induced, endothelium-dependent vasodilation.

Effects of hyperthyroidism on vascular contractile and relaxation responses.

Previous research has shown that skeletal muscle blood flow, at rest and during muscular contractions, is elevated in the hyperthyroid state. We hypothesized that reduced vascular contractile and enhanced endothelium-dependent relaxation responses contribute to these observations. To test these hypotheses, male rats were administered triiodothyronine (Hyper, n = 27; 300 micrograms/kg) for 6-12 wk. Compared with euthyroid control rats (Eut, n = 27), Hyper exhibited left ventricular hypertrophy (Eut, 2.01 +/- 0.04 mg/g body wt; Hyper, 2.70 +/- 0.06; P < 0.0005) and greater oxidative enzyme activity in several skeletal muscles (all P < 0.0005). Vascular rings, 2-3 mm in axial length, were prepared from abdominal aortas, and responses to vasoactive agents were determined in vitro. Compared with Eut, vascular rings with intact endothelium from Hyper exhibited reductions in contractile responses to norepinephrine (NE) across a range of NE concentrations (P < 0.05). Maximal tension developed in response to NE was reduced approximately 30% in hyperthyroidism (Eut, 3.8 +/- 0.2 g; Hyper, 2.6 +/- 0.4; P < 0.01). Contractile responses to NE were not different between Eut and Hyper in rings denuded of endothelium. Maximal vasorelaxation responses to acetylcholine (ACh), after precontraction with NE (10(-7) M), were enhanced in the hyperthyroid state (Eut, 65.1 +/- 4.8%; Hyper, 84.0 +/- 7.1; P < 0.05). Enhanced vasorelaxation to ACh was also observed when precontraction was induced by prostaglandin F2 alpha. These findings indicate that vascular contractile and relaxation responses are altered in male hyperthyroid rats.

Evidence for immune system involvement in reflex sympathetic dystrophy.

Skin biopsies from patients with reflex sympathetic dystrophy were immunostained using a variety of antisera. An incidental finding with S100 staining was the presence of numerous Langerhans cells in the epidermis. All patients had significant pain at the time of biopsy, and all had symptoms refractory to treatment. The potential implications of this finding are discussed.

Adaptations in control of blood flow with training: splanchnic and renal blood flows.

Acute exercise is associated with large increases in cardiac and active skeletal muscle blood flows and reduced blood flows to inactive muscle, skin, kidneys, and organs served by the splanchnic circulation. Splanchnic and renal blood flows are reduced in proportion to relative exercise intensity. Increased sympathetic nervous system outflow to splanchnic and renal vasculature appears to be the primary mediator of reduced blood flows in these circulations, but the vasoconstrictors angiotensin II and vasopressin also make important contributions. Human and animal studies have shown that splanchnic and renal blood flows are reduced less from resting levels during acute exercise after a period of endurance exercise training. Investigations of mechanisms involved in these adaptations suggest that reductions in sympathetic nervous system outflow, and plasma angiotensin II and vasopressin concentrations, are involved in lesser splanchnic and renal vasoconstriction exhibited by trained individuals. In addition, a reduced response to the sympathetic neurotransmitter norepinephrine in renal vasculature may contribute to greater blood flow to the kidney during acute exercise after training. Greater splanchnic and renal blood flows during acute exercise following training are potentially beneficial in that disturbance from homeostasis would be less in the trained state. Additionally, increased splanchnic blood flow in the trained state may confer benefits for glucose metabolism during prolonged exercise.

Skeletal muscle biochemical adaptations to exercise training in miniature swine.

The primary purpose of this study was to test the hypothesis that endurance exercise training induces increased oxidative capacity in porcine skeletal muscle. To test this hypothesis, female miniature swine were either trained by treadmill running 5 days/wk over 16-20 wk (Trn; n = 35) or pen confined (Sed; n = 33). Myocardial hypertrophy, lower heart rates during submaximal stages of a maximal treadmill running test, and increased running time to exhaustion during that test were indicative of training efficacy. A variety of skeletal muscles were sampled and subsequently assayed for the enzymes citrate synthase (CS), 3-hydroxyacyl-CoA dehydrogenase, and lactate dehydrogenase and for antioxidant enzymes. Fiber type composition of a representative muscle was also determined histochemically. The largest increase in CS activity (62%) was found in the gluteus maximus muscle (Sed, 14.7 +/- 1.1 mumol.min-1.g-1; Trn, 23.9 +/- 1.0; P < 0.0005). Muscles exhibiting increased CS activity, however, were located primarily in the forelimb; ankle and knee extensor and respiratory muscles were unchanged with training. Only two muscles exhibited higher 3-hydroxyacyl-CoA dehydrogenase activity in Trn compared with Sed. Lactate dehydrogenase activity was unchanged with training, as were activities of antioxidant enzymes. Histochemical analysis of the triceps brachii muscle (long head) revealed lower type IIB fiber numbers in Trn (Sed, 42 +/- 6%; Trn, 10 +/- 4; P < 0.01) and greater type IID/X fiber numbers (Sed, 11 +/- 2; Trn, 22 +/- 3; P < 0.025). These findings indicate that porcine skeletal muscle adapts to endurance exercise training in a manner similar to muscle of humans and other animal models, with increased oxidative capacity. Specific muscles exhibiting these adaptations, however, differ between the miniature swine and other species.

Short-term exercise training alters responses of porcine femoral and brachial arteries.

The primary purpose of this study was to test the hypothesis that short-term exercise training enhances endothelium-dependent relaxation of porcine femoral and brachial arteries. Miniature swine ran on a treadmill for 1 h at 3.5 miles/h, twice daily, for 7 consecutive days (Trn; n = 8). Compared with sedentary controls (Sed; n = 7), Trn swine exhibited increased skeletal muscle citrate synthase activity (P < 0.05). Vascular rings approximately 3 mm in axial length were prepared from segments of femoral and brachial arteries, and responses to vasoactive agents were determined in vitro. Sensitivity to bradykinin (BK) was enhanced in brachial vascular rings from Trn swine compared with those from Sed swine, as indicated by lower concentration of vasorelaxing agent eliciting 50% of maximal response values [Sed, 8.63 +/- 0.09 (-log M); Trn, 9.07 +/- 0.13; P < 0.05]. This difference between groups was preserved in brachial rings in which formation of nitric oxide and vasodilator prostaglandins were inhibited [Sed, 8.57 +/- 0.17 (-log M); Trn, 8.97 +/- 0.13; P < 0.05]. Sensitivity to BK was not different between Sed and Trn in femoral arterial rings. Relaxation responses to the calcium ionophore A-23187 and sodium nitroprusside were not altered with training. Femoral and brachial arterial rings from Trn swine, compared with those from Sed swine, exhibited augmented vasocontraction across a range of concentrations and increased sensitivity to norepinephrine (all P < 0.05). These findings indicate that responses of porcine femoral and brachial arteries change in response to short-term training. Together with findings from previous studies involving longer term training, our data suggest that vascular adaptations may differ at different time points during long-term endurance exercise training.