Whereas mobilization of intracellular Ca 2 1 stimulates neuronal adenylyl cyclase via Ca 2 1 /calmodulin, mobilized Ca 2 1 directly inhibits adenylyl cyclase in other tissues. To determine the physiologic role of the Ca 2 1 -dependent interaction between Na 1 /Ca 2 1 exchange and b -adrenergic signal transduction in the intact heart, digoxin (0.3 mg/kg) was administered intravenously in rabbits...

The ergot alkaloid ergovaline has demonstrated a persistent and sustained contractile response in several different vascular models. It was hypothesized that different alkaloids isolated from tall fescue (Lolium arundinaceum) will contribute to this contractile response differently. The objective was to compare contractile-response patterns of single additions of the ergoline alkaloids lysergic...

Voltage-clamp experiments were performed on isolated single frog (Rana catesbeiana or Rana pipiens) atrial cells to determine the voltage-contraction relations of the single cardiac cell. The contractile responses of the single cell associated with long duration (3 second) depolarizing steps consisted of a rise to peak (phasic) followed by a decay to a sustained contraction (tonic). These phasi...

Hypoxia (0% O2) evokes a late-phase, endothelium-dependent contractile response in porcine isolated pulmonary arteries that may be caused by a cyclooxygenase-independent, endothelium-derived contractile factor. The aim of this study was to further analyze the mechanism underlying this hypoxic response. Proximal porcine pulmonary arterial rings were suspended for isometric tension recording in o...

To examine mechanisms by which cardiac tissue regulates the /S-adrenergic receptor and physiological response to /9-adrenergic agonists, we studied the effects of cytoskeletal disrupting agents and inhibition of protein synthesis on receptor properties and contractile response to isoproterenol in intact cultured ventricular cells from embryonic chick heart. Thirty minutes of exposure of intact ...

To examine mechanisms by which cardiac tissue regulates the beta-adrenergic receptor and physiological response to beta-adrenergic agonists, we studied the effects of cytoskeletal disrupting agents and inhibition of protein synthesis on receptor properties and contractile response to isoproterenol in intact cultured ventricular cells from embryonic chick heart. Thirty minutes of exposure of int...

Background & Aims: Considering the higher incidence of cardiovascular disorders in diabetes mellitus and some evidence on antioxidant and antidiabetic potential of Tribulus terrestris (TT), this study was conducted to evaluate the beneficial effect of 6-week oral administration of TT on contractile reactivity of isolated thoracic aorta in diabetic rats. Methods: Female Wistar rats were divided ...

Previous studies have documented that repetitive exposure to intermittent hypoxia, such as that encountered in preparation to high-altitude ascent, influences breathing. However, the impact of intermittent hypoxia on airway smooth muscle has not been explored. Ascents to high altitude, in addition to hypoxia, expose individuals to cold air. The objective of the present study is to examine the e...

Vasoconstriction is a response associated with consumption of toxic endophyte-infected tall fescue. It is not known if endophyte-produced alkaloids act alone or collectively in mediating the response. Therefore, the objective of this study was to examine the vasoconstrictive potentials of selected ergot alkaloids, individually or in paired combinations, using bovine lateral saphenous veins biop...