Jp. Tolvanen et al., VARIATIONS OF ARTERIAL RESPONSES IN-VITRO IN DIFFERENT SECTIONS OF RAT MAIN SUPERIOR MESENTERIC-ARTERY, Pharmacology & toxicology, 83(2), 1998, pp. 75-82
We examined the control of vascular tone in rat main superior mesenter
ic artery. Three standard rings (3 mm in length) of the mesenteric art
ery were cut, beginning 5 mm, 13 mm and 21 mm distally from the mesent
eric artery-aorta junction. In noradrenaline-precontracted rings, rela
xations to acetylcholine in the absence and presence of the cyclooxyge
nase inhibitor diclofenac, did not differ in the studied sections. How
ever, the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl
ester, attenuated the diclofenac-resistant responses to acetylcholine
more effectively in the proximal than the distal section. Glibenclamid
e, an inhibitor of ATP-sensitive K+ channels, diminished relaxations e
voked by acetylcholine only in the distal section, whereas the inhibit
or of Ca2+ activated K+ channels, apamin, attenuated the responses in
all sections. Furthermore, relaxation sensitivity to nitroprusside and
isoprenaline was lower in the proximal than distal section. Arterial
contractile sensitivity to noradrenaline and potassium chloride was hi
gher, while the maximal contractile force generation was lower in the
proximal than the distal part. In conclusion, in different sections of
rat main superior mesenteric artery considerable variability was obse
rved in vasoconstrictor and vasodilator responses, as well as in the c
ontribution of endothelial nitric oxide and endothelium-mediated hyper
polarization to vasodilation. Therefore, the present results emphasize
the fact that only corresponding vessel segments should be used when
investigating the control of arterial tone.