Vaso-pressin

In normal clinical use the peak plasma fluoride concentration rarely exceeds 25 pmohL-l and is well within the threshold for renal toxicity. Significant renal impairment is unlikely in patients with normal renal function. Prolonged enflurane anaesthesia may result in vaso-pressin-resistant type of renal failure with fluoride concentrations of around 30 pmohL-l In contrast to methoxyflurane peak fluoride concentrations occur early (3-4 h) after enflurane and diminish rapidly after discontinuing the agent. 

The renin—angiotensin—aldosterone and sympathetic nervous systems are the main homeostatic effectors of vasoconstriction and sodium retention, paralleled by vaso-pressin/adiuretin activation. They all act synergistically but, at the same time, are balanced by counter-regulatory vasodilator and natriuretic mechanisms, particularly the natriuretic peptides and the NO system, also interplaying with endothelial redox systems, inflammatory cytokines and growth factors (Kaplan, 2002). 

Sympathins, the sympathomimetic substamces liberated in the heart, intestine, and elsewhere as the result of adrenergic stimulation one of them has been identified with adrenaline. Natural compounds with a sympathin effect are vaso-pressin (p. 349), tyramine, /-adrenaline, hordenine (an alkaloid from barley) and /-ephedrine (an alkaloid from the Chinese plant. Ephedra... 

Summary.— The principal vaso-pressor factors obtained from natural sources are tyramine, tryptamine, ephedrine, adrenine and pituitary vaso-pressin. 

Posterior pituitary Anti-diuretin. Vaso-pressin. Oxytocin. Diuresis control. Vaso-constriotor. Muscle contraction. 

Vaso-pressin, jS-hypophamine, causes contraction of capillaries and arterioles after injection. The blood pressure slowly rises and remains high for several hours. There is little change in the rate and force of the heart beat other than that due to increased vascular resistance. 

Injection of a second dose after the pressor effects of the first have worn off usually causes little or no response, the vascular system remaining insensitive for several hours. This may be due to the appearance of an anti-vaso-pressin in the organism, or, more likely, to the exhaustion of a contractile factor in the vessel walls. Birds for some unexplained reason appear to be immune from the vasopressor action of pituitary extracts. In man, the constricting effect on the capillaries is very conspicuous in the blanching of the skin that follows subcutaneous injection. 

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