Birgitta Arneklo-Nobin

Non-specific steroidal esterase activity and distribution in human and other mammalian tissues

An NADPH dependent arylamine carcinogen and fatty acid steroid ester metabolizing esterase activity belonging to the B- or carboxylesterase class of non-specific esterase (EC 3.1.1.1) was measured by two different methods: (i) a spectrophotometric assay using alpha naphthyl acetate (ANA) as substrate and (ii) a radiometric method using the conversion of beclomethasone-17,21-dipropionate to beclomethasone-17-monopropionate as the endpoint. The two methods were strongly correlated when assayed in human mononuclear leukocytes (r = 0.89, P < 0.0001) and human mammary tissue (r = 0.91, P < 0.0001). Hence it was concluded that the two substrates are metabolized at least in part by the same enzyme. This esterase activity was abundant in human monocytes, present in T-lymphocytes and equally divided between CD4 and CD8 T-lymphocyte subsets. The same activity was expressed in human liver, colon, stomach, breast and brain tissues. The distribution of this esterase in human tissues showed high activity in liver, intermediate activity in colon, stomach and breast and low activity in brain tissue. The interorgan distribution observed in human tissues was closely mimicked when the esterase activity was assessed in liver, colon and brain tissues from three mouse strains and three rat strains. The non-specific steroidal esterase activity determined by ANA metabolism in human mammary tissue was shown to be reproducible when assayed as triplicate samples from each of 16 different women (intraclass correlation coefficient 67.3%, P < 0.03). The interindividual variation in mammary tissue was high (18.4-fold) and there was a positive correlation between the esterase activity and age (r = 0.58, P < 0.01), as well as a tendency toward bimodal distribution. To our knowledge, these data represent the first systematic study of interorgan and interspecies comparisons of a non-specific steroidal esterase activity.

Cooling augments contractile response to 5-hydroxytryptamine via an endothelium-dependent mechanism.

The interaction between cooling and vasoactive substances, e.g. 5-hydroxytryptamine (5-HT), plays an important role in the pathophysiology of cold-induced vasospasm. Our objective was to study the effect of cooling on the 5-HT vascular response, classify the involved 5-HT receptors, and to analyze the role of the endothelium. Ring segments from the rat jugular vein, a preparation without alpha-adrenergic receptors, were suspended in organ baths to record the circular motor activity. The temperature was initially 37 degrees C and was thereafter either continuously lowered to 10 degrees C or kept constant at different temperatures within this range. 5-HT at low concentrations (10(-11) to 3 x 10(-8) M) induced relaxation at 37 degrees C in segments precontracted by prostaglandin F2 alpha. The relaxation was recognized to be mediated via an endothelium-dependent 5-HT1-like receptor mechanism presumably involving the release of endothelium-derived relaxing factor (EDRF). Cooling to 29 and 20 degrees C diminished the relaxation, probably due to an attenuated release of EDRF. 5-HT at concentrations of more than 10(-8) M induced a contraction in all vessels at 37 degrees C mediated via a 5-HT2 receptor. An increased 5-HT-induced contraction was seen at temperatures below 37 degrees C in vessels with an intact endothelium. Endothelial denudation diminished the cold-induced enhancement of the contraction to 5-HT. These studies suggest that endothelial mechanisms contribute to a cold-induced augmented response to 5-HT.

Adrenergic and Serotoninergic Mechanisms in Human Hand Arteries and Veins Studied by Fluorescence Histochemistry and in vitro Pharmacology

Isolated hand arteries and veins from healthy human subjects were tested in vitro for their contractile response to adrenergic agonists and 5-hydroxytryptamine (5-HT) under standardized conditions. This allowed for quantitative estimation of various receptor characteristics. The relative sympathomimetic potency suggested alpha-adrenergic receptors, which was confirmed in Schild plots following phentolamine antagonism of the response (pA2 for artery 7.57, for vein 7.75). 5-HT contracted with a relative potency approximately equal to noradrenaline and adrenaline in arteries, but only one fifth to one tenth of the catecholamine activity in veins. Ketanserin inhibited the 5-HT response in a competitive, probably also irreversible, manner in arteries (pA2 9.50, KA 8.90 X 10(-7) M). In the veins, ketanserin counteracted the 5-HT-induced contraction in a noncompetitive way.

Heterogeneity of contractile 5-HT receptors in human hand veins

To increase our knowledge of human peripheral vasospasm we characterized the contractile 5-hydroxytryptamine (5-HT) receptors in human superficial hand vein segments in vitro. The 5-HT1 receptor agonist, sumatriptan, the 5-HT2 receptor agonist, dl-alpha-methyl-5-HT, and the 5-HT3 receptor agonist, 2-methyl-5-HT, all induced concentration-dependent contractions. The contractile response to sumatriptan was antagonized by the non-selective 5-HT receptor antagonist, methiothepin, but was unaffected by the 5-HT2 receptor antagonist, ketanserin. The contractile response to dl-alpha-methyl-5-HT was antagonized by both methiothepin and ketanserin. The contraction elicited by 2-methyl-5-HT was not affected by the 5-HT3 receptor antagonist, MDL 72222, but was antagonized by ketanserin. The results suggest that serotonergic contraction in the human superficial hand vein involves both 5-HT1 and 5-HT2 but not 5-HT3 receptors. Such receptor heterogeneity in human blood vessels should be considered when using drugs and when designing future compounds for medical use.

Indications for angiography and its optimal performance in patients with Raynaud's phenomenon

Fifty-two patients with Raynauds phenomenon of the upper extremity were examined by angiography because of suspected organic stenosis or occlusions in areas available for reconstructive vascular surgery. Different vasodilatating treatments were compared either singly or combined: blockade of the brachial plexus, intraarterial injections of phentolamine or reserpine, body warming, and orally administered alcohol. Body warming in combination with 4 mg phentolamine gave optimal vasodilatation within the shortest time and without vasospasm after local cold provocation in patients with sympathetically induced vasospasm, enabling a clear visualization of organic lesions. A proper vasodilatation was also obtained after blockade of the brachial plexus or reserpine injection combined with body warming, but not until 40 min after the start of the treatments.