[Changes in transcapillary fluid exchange and the distensibility of small intestinal blood vessels upon adrenergic stimulation].

In acute experiments on cats, the mean coefficient of capillary filtration (CFC) in denervated small intestine was 0.10 ml/min/mm Hg/100 g and the stretching ability of the intestinal venous vessels was 0.21 ml/mm Hg/100 g. Infusion of noradrenaline (5 micrograms/min) reduced the CFC by 33% and the stretching ability by 24%. Blockade of vascular alpha-adrenoreceptors abolished and beta-adrenoreceptors augmented the noradrenaline effect on CFC and stretching ability. The data obtained indicate presence of both alpha- and beta-adrenoreceptors in precapillary sphincters and venous vessels of small intestine. Stimulation of the alpha-adrenoreceptors entails constriction of precapillary sphincters and decreases venous stretching ability whereas stimulation of beta-adrenoreceptors leads to opposite effects. Noradrenaline exerts main effect on alpha-adrenoreceptors of precapillary sphincters and venous vessels in the denervate intestine; alpha-blockade is followed by an obvious beta-effect in the form of relaxation of precapillary sphincters and increase of the venous stretching ability.