Heterogeneity of membrane properties in vascular muscle cells from various vascular beds.

It is becoming increasingly more apparent that vascular smooth muscle cannot be treated as a homogeneous group and cannot be compared to other types of smooth muscle at least in terms of responsiveness to vasoactive agents. This heterogeneity may have as part of its basis differences in the molecular structure at the level of the plasma membrane. Such differences manifest themselves in terms of resting membrane potential (Em), response to cardiac glycosides, ionic conductances, and membrane responses to neurotransmitters. Results show that the middle cerebral artery of the cat has a higher Em and depolarizes to excess K+ with a steeper slope than other peripheral arteries of the same animal. Furthermore, cerebral arteries from different areas of the brain exhibit distinctly different resting membrane properties as well as different responses to norepinephrine. In addition, cerebral arteries exhibit a high degree of electromechanical coupling not always observed in other peripheral arteries.