Lactate production of mammalian intestinal and vascular smooth muscles under aerobic and hypoxic conditions

Creatine kinase, energy reserve, and hypertension: from bench to bedside

We hypothesized that human variation in the activity of the ATP regenerating enzyme creatine kinase (CK) activity affects hypertension and cardiovascular disease risk. CK is tightly bound close to ATP-utilizing enzymes including Ca2+-ATPase, myosin ATPase, and Na+/K+-ATPase, where it rapidly regenerates ATP from ADP, H+, and phosphocreatine. Thus, relatively high CK was thought to enhance ATP-demanding processes including resistance artery contractility and sodium retention, and reduce ADP-dependent functions. In a series of studies of our group and others, CK was linked to hypertension and bleeding risk. Plasma CK after rest, used as a surrogate measure for tissue CK, was associated with high blood pressure and failure of antihypertensive therapy in case-control and population studies. Importantly, high tissue CK preceded hypertension in animal models and in humans, and human vascular tissue CK gene expression was strongly associated with clinical blood pressure. In line with this, CK inhibition substantially reduced the contractility of human resistance arteries ex vivo. We also presented evidence that plasma CK reduced ADP-dependent platelet aggregation. In subsequent intervention studies, the oral competitive CK inhibitor beta-guanidinopropionic acid (GPA) reduced blood pressure in spontaneously hypertensive rats (SHRs), and a 1-week trial of sub-therapeutic dose GPA in healthy men was uneventful. Thus, based on theoretical concepts, evidence was gathered in laboratory, case-control, and population studies that high CK is associated with hypertension and with bleeding risk, potentially leading to a new mode of cardiovascular risk reduction with CK inhibition.

Carbon dioxide-induced inhibition of mechanical activity in gastrointestinal smooth muscle preparations isolated from the guinea-pig

Mechanical responses of smooth muscle elicited by application of CO2-gas bubbled physiological salt solution (CO2-gas solution) were investigated in isolated stomach antrum and colon preparations of the guinea-pig. Circular smooth muscle preparations of both colon and stomach were spontaneously active with periodic generation of phasic contractions. In colonic preparations, the CO2-gas solution produced a biphasic response, with an initial small transient contraction followed by a sustained inhibition of phasic contractions. Removal of the CO2-gas solution allowed a slow recovery of the spontaneous contractions over a period of about 40 min. The recovery developed with a similar time course irrespective of the length of time exposed to CO2-gas solution. The inhibitory responses elicited by CO2-gas solution were not modulated by atropine, Nω-nitro-L-arginine or neostigmine. Atropine-sensitive excitatory responses of smooth muscle elicited by transmural nerve stimulation or exogenously applied acetylcholine were attenuated or abolished in the presence of CO2-gas solution. In stomach preparations, the CO2-gas solution elicited a tri-phasic response, with an initial transient relaxation followed by a transient contraction and then a sustained inhibition of the rhythmic contractions. The peak amplitude of the transient contraction was about 2.5 times larger than the spontaneous phasic contractions. The pH of the CO2-gas solution was reduced to about 6. Application of pH 6 solution again produced a tri-phasic response, as was the case for the CO2-gas solution, however the amplitude of the transient contraction was only about 0.4 times that of the spontaneous contractions. The re-appearance of the abolished phasic contraction was quicker with the pH 6 solution (about 1.8 min) than it was for the CO2-gas solution (about 6 min). The inhibitory responses elicited by the CO2-gas solution could be simulated only partly by the acidified solution, and a possible involvement of additional factors in the inhibition elicited by CO2-gas solution was considered.

Ethnic differences in resistance artery contractility of normotensive pregnant women

Black women are at a greater risk to develop hypertension during pregnancy, with a 4.5 times higher rate of fatal preeclampsia than white women. Therefore, it is important to identify factors that may affect this risk. Our group previously proposed that high activity of the central regulatory enzyme of energy metabolism, creatine kinase (CK), may increase ATP-buffering capacity and lead to enhanced vascular contractility and reduced nitric oxide bioavailability. Therefore, we assessed microvascular contractility characteristics in isolated resistance arteries from self-defined black and white normotensive pregnant women using a Mulvany-Halpern myograph. Additionally, morphology was assessed with electron microscopy. Resistance-sized arteries obtained from omentum donated during cesarean sections (11 black women and 20 white women, mean age: 34 yr) studied in series showed similar morphology but significantly greater maximum contractions to norepinephrine (10(-5) M) in blacks [14.0 mN (1.8 SE)] compared with whites [8.9 mN (1.4 SE), P = 0.02]. Furthermore, we found greater residual contractility after the specific CK inhibitor dinitrofluorobenzene (10(-6) M) in black women [55% (6 SE)] compared with white women [28% (4 SE), P = 0.001] and attenuated vasodilation after bradykinin (10(-7) M) in black women [103% (6 SE)] compared with white women [84% (5 SE), P = 0.023], whereas responses to sodium nitroprusside (10(-4) M) and amlodipine (10(-6) M) were similar. We conclude that compared with white women, normotensive pregnant black women display greater resistance artery contractility and evidence of higher vascular CK activity with attenuated nitric oxide synthesis. These findings in normotensives may imply that the black population is at risk for a further incline in pregnancy-related hypertensive disorders.

Comparison of lymphomononuclear cell energy metabolism between healthy, impaired glucose intolerance and type 2 diabetes mellitus patients

Diabetes mellitus (DM) is a complex disease that affects many systems. The most important cells of the immune system are lymphomononuclear (LMN) cells. Here, we aimed to evaluate the energy metabolism of LMN cells in patients with diabetes and impaired glucose tolerance. We measured LMN cell energy metabolism in patients with type 2 diabetes mellitus, impaired glucose tolerance (IGT) and healthy subjects. Cells were freshly isolated from peripheral blood and the subgroups were determined by flow cytometric method. Lactate production and glycogen utilization were significantly increased in the LMN cells of patients with type 2 DM and IGT when compared with healthy volunteers. No statistical difference was observed between the patients with type 2 DM and IGT. There was a significant correlation between fasting plasma glucose and lactate production in LMN cells. LMN cells changed their energy pathway in a diabetic state and preferred anaerobic glycolysis. Prediabetic range also affected energy metabolism in LMN cells. This abnormal energy production might cause dysfunction in LMN cells and the immune system in diabetic and prediabetic patients. In conclusion, we concluded that impaired glucose metabolism could change energy metabolism.

Vascular smooth muscle function: The physiology and pathology of vasoconstriction

Vascular smooth muscle is the contractile component of arteries and veins. The control of contraction and relaxation is dependent upon intracellular and extracellular signals. Abnormal contractions can cause and or contribute to pathology such as hypertension, ischemia and infarction. In this review, we address the vascular pathogenesis associated with hypertension and subarachnoid hemorrhage induced cerebral vasospasm. Hypertension is a multifactorial disease with many causes and a profound impact on the cardiovascular system, whereas subarachnoid hemorrhage induced cerebral vasospasm is a pathological vasoconstriction often causing infarction that is thought to be 'caused' by a factor or factors in the CSF following the hemorrhage. However, the mechanism by which the vessels are constricted is unknown. Although the causes for these two pathological vasoconstrictions remain to be determined, we conclude that the common denominator is that these contractile changes result in pathology with devastating consequences to human health.

Hypoxic vasorelaxation: Ca2+-dependent and Ca2+-independent mechanisms

The mechanisms of oxygen sensing in vascular smooth muscle have been studied extensively in a variety of tissue types and the results of these studies indicate that the mechanism of hypoxia-induced vasodilation probably involves several mechanisms that combined to assure the appropriate response. After a short discussion of the regulatory mechanisms for smooth muscle contractility, we present the evidence indicating that hypoxic vasorelaxation involves both Ca2+-dependent and Ca2+-independent mechanisms. More recent experiments using proteomic approaches in organ cultures of porcine coronary artery reveal important changes evoked by hypoxia in both Ca2+-dependent and Ca2+-independent pathways.