Prostaglandin E1 is a highly potent vasodilator in canine subcutaneous adipose tissue, whereas sympathetic nerve stimulation, histamine, and bradykinin significantly increase capillary permeability.
Abstract The circulatory effects of acetylcholine, bradykinin, isoprenaline, histamine, 5‐hydroxytrypt‐amine (5‐HT), noradrenaline and prostaglandin Ei (PGE 1 ) were studied in the canine subcutaneous adipose tissue. PGE 1 produced clearcut vasodilatations at calculated blood concentrations as low as 10 ‐9 M and was found to be the most potent of the drugs tested. PGE 1 was about 1000 times more potent than acetylcholine and about 10 times more potent than histamine. 5‐HT induced a moderate blood flow increase with no change or a decrease of tissue volume, indicating a constriction of the venous section. The vascular responses to noradrenaline infusions were essentially similar to those produced by sympathetic nerve activation, i.e . constriction of arterioles and veins and a markedly increased capillary filtration coefficient (CFC). Histamine and bradykinin induced increases of CFC of the same magnitude as did sympathetic nerve stimulation, whereas acetylcholine, isoprenaline, 5‐HT and PGE 1 induced smaller increases of CFC. Sympathetic nerve stimulation superimposed upon infusions of the latter drugs produced a further marked increase of CFC, while nerve stimulation applied during a period of histamine or bradykinin infusion produced no further rise or even a decrease of CFC. It is discussed that the pronounced CFC increase during sympathetic nerve stimulation is due to an increased permeability of the capillary membrane.
Fredholm et al. (Sat,) studied this question.
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