Caveolar bands and the effects of sterol-binding agents in vascular smooth muscle plasma membrane. Single and double labeling with filipin and tomatin in the aorta, pulmonary artery, and vena cava.
The effects of single and sequential double treatment with the sterol probes filipin and tomatin were investigated in relation to the distribution of caveolae (flask-shaped membrane invaginations) in the smooth muscle plasma membrane of rabbit aorta, pulmonary artery, and posterior vena cava. The principal structural characteristics of vascular smooth muscle caveolae are documented, and the effects of filipin are quantitatively evaluated and compared in the three vessel types. Aortic and pulmonary artery smooth muscle cells were found to resemble one another with respect to caveolar banding pattern and response to filipin. By comparison, however, the caveolar bands of vena cava smooth muscle were aligned with remarkable precision and regularity, and proved to be significantly (p less than 0.001) more sensitive to filipin than those of the arterial cells. The noncaveolar interband zones in all vessels were resistant to filipin action but sensitive to tomatin. Again, this sensitivity was more marked in vena cava smooth muscle than in arterial smooth muscle. The precision of caveolar banding, combined with the accentuated effects shown by each agent in the vena cava made the result of sequential double filipin-tomatin labeling outstandingly clear-cut in this vessel, with alternate filipin-affected and tomatin-affected zones superimposed, respectively, upon the caveolar bands and interbands. These findings strengthen the view that cholesterol distribution in the smooth muscle plasma membrane is homogeneous, and that the resistance of the smooth muscle interband membrane to filipin is a false-negative cytochemical result due to the presence of underlying membrane associated dense bodies.
D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D002784:Cholesterol / Q000378:metabolism; D005372:Filipin / Q000494:pharmacology*; D005614:Freeze Fracturing; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000648:ultrastructure*; D011090:Polyenes / Q000494:pharmacology*; D011651:Pulmonary Artery / Q000648:ultrastructure; D011817:Rabbits; D013997:Time Factors; D014053:Tomatine / Q000494:pharmacology*; D014682:Vena Cava, Inferior / Q000648:ultrastructure
D000470:Alkaloids; D008563:Membrane Lipids; D011090:Polyenes; D014053:Tomatine; D005372:Filipin; D002784:Cholesterol