J.O.G. Karlsson

Effects of ultraviolet radiation on the tension and the cyclic GMP level of bovine mesenteric arteries

Strips of bovine mesenteric arteries brought to sustained contraction by the addition of 3.0 microM phenylephrine relaxed when exposed to ultraviolet radiation (366 nm). The relaxation was reversible and associated with a rapid increase in the cGMP content. After termination of the radiation the cGMP level rapidly decreased below the basal level. The crude soluble guanylate cyclase from the artery was stimulated about 8-fold by ultraviolet radiation (366 nm). Neither the cGMP-phosphodiesterase activity nor the cAMP level were found to be changed during irradiation. The ultraviolet light-induced relaxation was not dependent on an intact intimal surface. Furthermore, the relaxing effect was found to be enhanced and accompanied by a larger increase of the cGMP level in nitroglycerin-tolerant arteries. The present results show that the ultraviolet light-induced relaxation in bovine mesenteric arteries is associated with a rapid increase in the cGMP content and that ultraviolet light and nitrocompounds may exert their relaxing actions through a common substance.

Fish scales as biosensors

Abstract It is demonstrated how certain fish scales (in our case from Cuckoo Wrasse, Labrus ossifagus) can be used for biosensing purposes. These scales contain cells with pigment granules which are either dispersed or aggregated. The pigments of an isolated fish scale are, e.g., aggregated by noradrenaline or other catecholamines. The aggregation can be measured by a simple photometer or by fibre optical probes. The sensitivity is very large. Nanomoles of noradrenaline can be easily measured. We discuss therefore the possibility of developing sensor probes for clinical use based on the fish scales.

Glyceryl trinitrate inhibits phosphatidylinositol hydrolysis and protien kinase C activity in bovine mesenteric artery

The effect of glyceryl trinitrate (GTN) on relaxation, cGMP levels, phosphorylase a activity, phosphatidylinositol hydrolysis and protein kinase C activity was studied on isolated bovine mesenteric arteries (BMA). Two concentrations of GTN were tested, 0.1 nM representing a high affinity component and 1 microM representing a low affinity component of the GTN induced relaxation of BMA, giving a relaxation of 20% and 60% and a 2-fold and 5-fold increase in cGMP, respectively. Phosphatidylinositol hydrolysis and protein kinase C activity were significantly, and to the same extent, reduced at both concentrations tested, whereas the phosphorylase a activity was significantly reduced at the higher concentration only, which might indicate a reduction of the free intracellular Ca2+-concentration at high concentrations of GTN. It is concluded that a therapeutically relevant concentration (0.1 nM) of GTN induces relaxation and an increase in cGMP in bovine mesenteric arteries. The relaxation seems to be associated with an inhibition of phosphatidylinositol hydrolysis and a reduction of the protein kinase C activity.

Effects of sodium nitrite on ultraviolet light-induced relaxation and ultraviolet light-dependent activation of guanylate cyclase in bovine mesenteric arteries

It was demonstrated that precontracted strips from different bovine mesenteric arteries showed variation in sensitivity to ultraviolet radiation (366 nm). Some strips relaxed when they were exposed to ultraviolet light, others showed no sensitivity at all and, finally, some showed contraction. However, all arteries relaxed when they were irradiated with UV-light in the presence of 10 microM NaNO2. Ultraviolet radiation (366 nm) increased the activity of guanylate cyclase in crude homogenate from bovine mesenteric arteries by about 20-fold in the presence of NaNO2, while UV-light in the absence of sodium nitrite had no effect on the guanylate cyclase activation. These results support the notion that nitrite may be essential for vascular smooth muscle relaxation by UV-light, possibly through the release of nitric oxide.

Effects of pertussis toxin on vasodilation and cyclic GMP in bovine mesenteric arteries and demonstration of a 40 kD soluble protein ribosylation substrate for pertussis toxin

The inhibitory nucleotide-regulatory protein (Gl) has been shown to lose its adenylate cyclase inhibitory effect upon treatment with pertussis toxin. To find out whether a pertussis sensitive mechanism is involved in the regulation of the cGMP-system, bovine mesenteric arteries were incubated in buffer containing pertussis toxin, and the relaxation and intracellular cGMP accumulation induced by different groups of vasodilating agents were studied. The present results show a pertussis toxin induced decrease in relaxation as well as a decrease in the cGMP-elevation induced by the endothelium dependent vasodilators acetylcholine and calcium ionophore A 23187. Arteries treated with atrial natriuretic peptide showed no alterations in relaxation or cGMP content after incubation with pertussis toxin. A 40 kD soluble ribosylation substrate for pertussis toxin was identified in bovine mesenteric artery. These results suggest that a pertussis toxin sensitive mechanism is involved in the vasodilating mechanism of acetylcholine and calcium ionophore A 23187, while no evidence for such a mechanism could be found regarding the vasodilatory action of atrial natriuretic peptide.

Optical biosensors based on fish pigment cells

Abstract Melanophores (black pigment cells) in isolated fish scales have the ability to either aggregate their intracellular pigment granules to the centre or disperse them throughout the cell. Noradrenaline stimulates aggregation within these cells. The sensitivity of noradrenaline is considerably increased after approximately one week of isolation of the scales in a tissue culture medium. In order to measure simultaneously pigment aggregation in several isolated scales, a multichannel fibre-optic system has been developed. The system enables the scales to be constantly perfused with tissue culture medium, which in turn allows measurements to be made over long periods of time. After nine days of isolation there is an approximately 12 000-fold increase in noradrenaline sensitivity. The fibre-optic system, combined with cultured melanophores and molecular biology techniques, should provide a number of interesting biosensing possibilities.

A pertussis toxin resistant alpha2-adrenoceptor pathway in fish melanophores

The effect of pertussis toxin (PT) on the aggregation of pigment granules in melanophores from cuckoo wrasse (Labrus ossifagus L.) was studied. The results indicate the presence of a PT resistant alpha 2-adrenoceptor signal transduction mechanism.

Fish-scale photometry and in vitro cytotoxicity

Abstract Certain fish scales contain thousands of black pigment cells (melanophores). Electrical stimulation of such a scale causes intrinsic nerves to release noradrenaline, which in turn aggregates the pigment within each melanophore. The aggregation is readily quantified by the aid of a simple fish-scale photometer. The probability of detecting toxic effects of chemicals (and their mode of action) is supposed to be quite good in such a system. The present contribution describes fish-scale photometry for in vitro estimation of acute toxicity of the first ten MEIC (Multicentre Evaluation of in vitro Cytotoxity) chemicals. The IC50 (50% inhibition of nerve-induced pigment aggregation) values of the tested chemicals (except one) are close to or far below the known lethal blood concentrations in man. By comparing these IC50 values with those of exogenously added noradrenaline, it is concluded that most of the tested chemicals mainly inhibit the nerve function. The present results suggest that fish-scale photometry may be of potential value as an inexpensive toxicity screening method.