Individualities in post-serotonin attenuation and Na+/K+ pump activity in vascular smooth muscle.
Prior treatment with serotonin (10(-8)-10(-7) M for 6 min) attenuated responses of rabbit mesenteric arteries to norepinephrine (NE) by 18-62%, but was without effect on the responses of the rabbit aorta. K+ relaxation responses in the mesenteric arteries were enhanced by serotonin, but in the aortic strips K+ relaxation occurred either before or after treatment with serotonin. Maximum relaxation to monensin was similar in the two tissues. Post-serotonin attenuation and K+ and monensin relaxation were blocked by ouabain, indicating that they depended on Na+/K+ pump stimulation. Intracellular Na+ contents (Nai) were determined in the vessels by the Li substitution method. Nai was greater, and was increased to a greater extent by serotonin and K(+)-free physiological salt solution in the mesenteric artery compared to the aorta, suggesting that the cell membrane of the mesenteric artery is leakier to Na+ than is that of the aorta. We conclude that the absence of post-serotonin attenuation in the aorta results from the failure of serotonin to increase Nai and thereby to stimulate the Na+/K+ pump in this tissue. This study demonstrates that important individualities in vascular smooth muscle reactivity even in the same animal may result from differences in membrane permeability to sodium.
Bell
D R
DR
Department of Physiology, University of Michigan, Ann Arbor 48109-0010.
Babcock
C M
CM
Bohr
D F
DF
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001693:Biological Transport, Active; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D008985:Monensin / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D011817:Rabbits; D012701:Serotonin / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D013054:Spectrophotometry, Atomic
D012701:Serotonin; D010042:Ouabain; D008985:Monensin; D012964:Sodium; D011188:Potassium; D009638:Norepinephrine