The blood circulation inside the spleen. I. The arterial blood vessels general distribution in the rat spleen.

As an attempt to investigate the different pathways followed by the blood into the spleen and to analyse their functional significance, a technique was used mainly based on the intraarterial perfusion of a Prussian blue "solution" added of some chemical mediators and vasoactive substances. Such technique provides results which may be analysed taking into account the effect of the anaesthetic used, that may influence the findings. From the anaesthetic used, the sulfuric ether and the barbital sodium produce vasoconstriction of the white pulp blood vessels, whereas the chlorpromazine-promethazine doesn't have this effect, and so the Prussian blue appears inside these vessels. The vasodilator drugs, such as succinonitrile and papaverine hydrochloride, show a general vasodilator effect on the splenic arterial system. Teh arterial vessels of the white and the red pulp, including those placed at the subcapsular areas, become enlarged; into the white pulp, either the central or the peripheral blood vessel plexus of the lymphatic follicle becomes evident. The latter readily constitutes the perifollicular and the pericolumnar plexus. The blood vessels of this plexus become permeable to the Prussian blue "solution" by the heparin sodium effect, and so the dye particles enter the marginal zone and the splenic sinuses. In addition, from the white pulp arteries arise 2 types of anastomotic arterioles which appear enlarged after succinonitrile treatment: The short anastomotic arterioles that crosses the marginal zone entering the red pulp near the white pulp; the long anastomotic arterioles which enter the red pulp and after a long course end up into or around a collector sinus. The addition of histamine dihydrochloride to the perfusion solutions shows a slight vasodilator effect mainly on the subcapsular penicillar arterioles, including the helicine arterioles. The adrenergic stimulation of the splenic blood vessels induces a generalized arterial constriction, except of the anastomotic arterioles, that becomes open; in such way, the blood pathway follows the course of the anastomotic arterioles and the collector arterioles also become constricted. The adrenergic vasoconstrictor effect is inhibited by the phenoxy-benzamine hydrochloride. The addition of acetylcholine chloride, in the dosage, used, induces a generalized arterial vessel constriction, mainly of the perifollicular plexus. This effect is inhibited by atropine sulfate which, on the other hand, produces evident enlargement of the perifollicular and pericolumnar arterial plexus.