Pharmacology of arterioles versus venules: an overview.

Although a considerable amount of information exists regarding the pharmacology, physiology and biochemistry of arterial and venous smooth muscles, little in the way of such precise quantitative information exists with respect to arterioles and venules within different regions of the microvasculature. From the available data, it is clear that microvessels from within a single microvasculature, as well as in different regions of the circulation, display heterogeneity with respect to their physiology, pharmacology and biochemistry. Differences in receptor sub-populations and composition exist along the microvascular tree as well as varying degrees of autonomic innervation and neurotransmitters between different microvessels. Although these factors in themselves are important in conferring microvasculature heterogeneity, a number of other physiologic, pharmacologic as well as experimental factors also seem to be a critical; included here are endothelial cells, sex hormones, ionic milieu, membrane composition, geometry, tissue metabolism, diet, physiologic state of host, anesthesia-analgesia, buffers, route of drug administration, etc. It is rather obvious that design of therapeutic drugs for specific cardiovascular problems must perforce take such factors into careful consideration.