cyclic-gmp and norathyriol

We examined the mechanisms of norathyriol on the serotonin-induced increased permeability of rat heart endothelial cell monolayers. The present study showed that the activation of rat heart endothelial cell protein kinase C by phorbol myristate acetate led to the dose-dependent increase in endothelial permeability to albumin, an effect that was inhibited by staurosporine (a protein kinase inhibitor). Staurosporine also attenuated the serotonin-induced increase in permeability. Norathyriol abolished both serotonin- and phorbol myristate acetate-induced permeability. We investigated whether norathyriol, by inhibiting protein kinase C activation, attenuated the serotonin-induced permeability. Immunofluorescence studies demonstrated that norathyriol prevented the redistribution of protein kinase C isozymes following stimulation with serotonin. Western blot analysis showed that norathyriol significantly inhibited the serotonin-induced translocation of the alpha protein kinase C isozyme from the cytosolic to the particulate fraction. In conclusion, norathyriol attenuates the serotonin-induced permeability of rat heart endothelial cells to macromolecules in association with inhibition of protein kinase C activation. This decrease in endothelial cell permeability may be one of the mechanisms for the protective effects of norathyriol against edema formation in response to inflammatory agonists in vivo.

Topics: Animals; Cell Membrane Permeability; Cells, Cultured; Cyclic AMP; Cyclic GMP; Endothelium, Vascular; Enzyme Activation; Enzyme Inhibitors; Protein Kinase C; Rats; Serotonin; Serotonin Antagonists; Staurosporine; Tetradecanoylphorbol Acetate; Xanthenes

The pharmacological effects of norathyriol on isolated rat thoracic aorta were examined. In the high-K+ (60 mM) medium, Ca2+ (0.03 to 3 mM)-induced vasocontraction was inhibited concentration dependently by norathyriol. Given as pretreatment norathyriol (20 to 200 microM) also inhibited the norepinephrine (NE, 3 microM)-induced tonic contraction. However, the phasic contraction was inhibited only by high concentrations of norathyriol (200 and 400 microM). The tonic contraction elicited by NE was also relaxed by the addition of norathyriol. This relaxing effect of norathyriol was not antagonized by methylene blue (50 microM) or indomethacin (20 microM) and was still seen in denuded rat aorta. Although the cAMP level was not changed by norathyriol, the cGMP level was increased by a high concentration of norathyriol (400 microM). [3H]Inositol monophosphate formation caused by NE was not affected by norathyriol at concentration of either 100 or 400 microM. The 45Ca2+ influx caused by either NE or high K+ was inhibited by norathyriol in a concentration-dependent manner. It is concluded that norathyriol relaxed the rat thoracic aorta mainly by suppressing the Ca2+ influx through both voltage-dependent and receptor-operated calcium channels.

Topics: Animals; Aorta, Thoracic; Caffeine; Calcium; Calcium Radioisotopes; Cyclic AMP; Cyclic GMP; Female; In Vitro Techniques; Inosine Monophosphate; Male; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; Norepinephrine; Plants, Medicinal; Potassium; Rats; Rats, Inbred Strains; Xanthenes