Decreased release of nitric oxide from damaged endothelium is responsible for the impaired endothelium-dependent vasodilator responses found in animal models of vascular disease. Dietary supplementation with fish oils has been shown to augment endothelium-dependent relaxations, principally by improving the release of nitric oxide from injured endothelium. Using forearm venous occlusion plethysmography we studied vascular responses to 60, 120, 180 and 240 nmol/min of acetylcholine (an endothelium-dependent vasodilator) and 3, 6 and 9 nmol/min of glyceryl trinitrate (an endothelium-independent vasodilator) infused into the brachial artery in 23 patients with Type 2 (non-insulin-dependent) diabetes mellitus. NG monomethyl-L-arginine was employed to inhibit stimulated and basal release of nitric oxide from the endothelium. On completion of the baseline studies patients randomly received either fish oil or matching olive oil capsules in a double-blind crossover fashion for 6 weeks followed by a 6-week washout period and a final 6-week treatment phase. Studies, identical to the initial baseline studies, were performed at the end of the active treatment periods at 6 and 18 weeks. Fish oil supplementation significantly improved forearm blood flow responses to each dose of acetylcholine when compared to the vasodilator responses recorded at baseline and after olive oil administration (p < 0.01). Neither fish oil nor olive oil supplementation produced any significant changes in forearm blood flow to the incremental infusions of glyceryl trinitrate when compared with responses recorded during the baseline studies.(ABSTRACT TRUNCATED AT 250 WORDS)

The potency of neuropeptide Y (NPY) to cause negative and positive contractile responses in rat ventricular cardiomyocytes was investigated. In these cells, NPY was found to activate the transient outward K+ current (Ito) and the slow inward Ca2+ current (Isi). As reported before (H. M. Piper, B. C. Millar, and J. R. McDermott, Naunyn Schmiedeberg's Arch. Pharmacol. 340: 333-337, 1989), NPY attenuated the increase in the contractile response induced by isoprenaline (10(-7) M). This effect of NPY could be abolished by 1) the presence of the inhibitor of Ito, 4-aminopyridine (4-AP, 0.5 mM); 2) pretreatment of the cells with pertussis toxin (1 microgram/ml for 6 h); and 3) the presence of the 19-amino acid COOH-terminal fragment of NPY, NPY-(18-36) (10(-6) M). In the absence of isoprenaline, but in the presence of 4-AP, NPY exerted a stimulatory effect on the cardiomyocytes. This effect could be abolished 1) by using the inhibitor of the Isi, verapamil (10(-8) M), but not 2) by pretreatment with pertussis toxin, nor 3) by coincubation with NPY-(18-36). The results indicate that in the rat the antiadrenergic negative contractile effect of NPY results from its action on the Ito. Blockade of this current by 4-AP unmasks a positive contractile effect of NPY that is related to activation of the Isi.

For studies on the regulation of myocardial protein metabolism, isolated adult cardiomyocytes were introduced as an experimental model about a decade ago. When used shortly after isolation, this model represents a tool for studying the properties of normal and diseased myocardium on the cellular level. The influence of various peptide hormones, neurotransmitters, and mechanical stimulation on protein synthesis and degradation in isolated cardiomyocytes has been studied. It has been demonstrated, for example, that alpha 1-adrenoceptor stimulation increases protein synthesis in newly isolated cardiomyocytes, independently of any mechanical effects. Other potential growth stimuli require appropriate conditions to induce cellular responsiveness. Neuropeptide Y, for example, does not stimulate cellular protein synthesis in newly isolated cells, whereas it does so in cells that have been cultured for a week in the presence of serum. Mechanical stretch also represents a growth stimulant. It seems that its signal transduction involves an autocrine loop. Thus different mechanisms, by which exogenous influences can modify cellular protein synthesis and degradation, have been identified on the cellular level, with the use of isolated adult cardiomyocytes.

The endothelium plays a pivotal role in modulating the reactivity of vascular smooth muscle through the formation of several vasoactive substances. We examined the effects of endothelium-dependent and independent vasodilators on forearm blood flow in 29 patients with Type 2 (noninsulin-dependent) diabetes mellitus and in 21 control subjects, using venous occlusion plethysmography. Via a brachial artery cannula, increasing amounts of acetylcholine and glyceryl trinitrate were infused in doses of 60, 120, 180 and 240 mmol per min and 3, 6 and 9 nmol per min respectively. N G monomethyl-L-arginine, a stereospecific inhibitor of endothelium derived relaxing factor, was infused to inhibit basal and stimulated release of this dilator substance. Reactive hyperaemic forearm blood flow did not differ between groups. Forearm blood flow responses to each dose of acetylcholine were significantly greater in control than diabetic subjects (p < 0.01 for all doses). N ~ monomethyl-L-arginine attenuated forearm blood flow from maximal stimulated values when responses were compared with the natural decline to acetylcholine in forearm flow in both control and diabetic subjects (p < 0.05 for both groups), but had no effect on basal blood flow responses. Forearm blood flow responses to each dose of glyceryl trinitrate were significantly greater in control than diabetic subjects (p < 0.05 for all). These data provide evidence for endothelial and smooth muscle dysfunction in diabetes which may have important therapeutic implications.

A 5-day continuous infusion of vincristine (VCR; total dose 4 mg/m2) has been given as part of a high-dose chemoradiotherapy regimen with bone marrow transplantation. Evidence of neurotoxicity, such as weakness, paraesthesia and intestinal hypomotility, was evaluated prospectively in nine patients. Five patients had advanced neuroblastoma and four, relapsed sarcomas, and all had responded to initial conventional-dose therapy. VCR was combined with high-dose melphalan (180 mg/m2) and fractionated total-body irradiation. Plasma concentrations of VCR were measured by radioimmunoassay during and up to 24 h after the infusion. Serum and urine electrolytes and liver function tests were measured during VCR treatment and at regular intervals thereafter. VCR concentration at 1 h ranged from 1.8 to 10.9 (median 6.6) ng/ml, and a steady state was achieved by 13-30 h (median 16 h). Levels above 1 ng/ml were maintained throughout the 5-day period with a mean steady-state concentration of 1.7 ng/ml (range 1.3-2.15). After cessation of the infusion, serum concentrations fell to below 0.25 ng/ml within 24 h. Abdominal pain occurred in one patient, but neither constipation nor ileus was seen. In two patients severe muscle pain occurred in the lower limbs towards the end of the infusion. Significant electrolyte problems did not occur and, in particular, there was no evidence of inappropriate ADH secretion. Transient increases in liver enzymes were common but bilirubin was not elevated during the period of monitoring. This regimen allows a two-fold escalation in the dose of VCR to be administered, producing sustained high serum drug levels without major toxicity.