Thalistyline, a monoquaternary bisbenzylisoquinoline alkaloid isolated from Thalictrum sp. inhibited respiration in anesthetized dogs. Thalistyline is about one-fourth as potent as d-tubocurarine in blocking neuromuscular transmission in the rat hemidiaphragm preparation. The pharmacological mechanism of action of the alkaloid is similar to that of d-tubocurarine. Obamegine did not exhibit curare-like activity. On the isolated rabbit aorta, contractions induced by an alpha-adrenoreceptor agonist, phenylephrine, were antagonized by both alkaloids. Increasing concentrations of thalistyline produced parallel shifts to the right in the dose-response curves of phenylephrine. The pA2 value for the competitive pharmacological antagonism was 6.33. Obamegine also antagonized the effects of phenylephrine on the aorta, line and obamegine lowered blood pressure in normotensive dogs. The effect was transient. Repeated injections of the alkaloids resulted in tachyphylaxis to blood pressure lowering effects. Although alkaloids exhibited alpha adrenergic blockade in the vascular preparation, the mechanism for the hypotensive effect remains to be established.
The synthesis of the cis-and írans-2-amino-l-phenylcyclobutanols 2 and 3 is described. The results of the potentiation of the action of (-)-norepinephrine by these two compounds are discussed.
Copper (Cu) metabolism is altered in rats fed diets high in molybdenum (Mo) and low in Cu. This 10-week study was carried out to examine the effects of supplemental Mo (7.5–240 μg/g diet) on male Sprague Dawley rats fed diets adequate in Cu (5 μg/g diet); and to determine the susceptibility of Mo-treated animals to the environmental pollutant 3,3′,4,4′-tetrabromobiphenyl (TBB). After seven weeks of dietary treatment, half the rats in each group received a single IP injection of TBB (150 μM/Kg bw), while the other half received the corn oil vehicle. Rats sacrificed at 10 weeks showed no effects of Mo on growth, feed efficiency, or selected organ or tissue weights. Dose-dependent effects on plasma Mo (0 – 5.1 μg/mL), Cu (0.95 – 0.20 μg/mL) and bone Cu (3.4 – 10 μg/g), in control through the high-dose were found. Cu sequestration in bone of Mo-treated rats is a new finding. TBB treatment resulted in dramatic weight loss and loss of absolute organ mass. Relative organ weights were increased, except for the thymus. TBB altered amino acid concentrations of certain amino acids. Compared to control rats, this polybrominated biphenyl congener significantly decreased plasma Cu and ceruloplasmin at higher concentrations of dietary Mo, and promoted the process of plasma Cu decrease by Mo, suggesting a combined effect.
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