Mfv. Dantas et al., Increased acetylcholine-induced vasodilation in pregnant rats - A role forgap junctional communication, HYPERTENSIO, 34(4), 1999, pp. 937-942
Citations number
31
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
We have tested the hypothesis that increased gap junctional communication c
ontributes to the augmented endothelium-dependent vasodilation in pregnancy
. Contractile force and connexin43 expression were measured in aortic rings
from nonpregnant and pregnant rats. Norepinephrine-constricted aortas from
pregnant rats were more sensitive to acetylcholine, but not to sodium nitr
oprusside, compared with those from nonpregnant rats. Vessels from pregnant
rats, constricted either with 45 mmol/L KCl or with norepinephrine + 10(-4
) mol/L N-G-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide sy
nthase, also exhibited greater relaxation to acetylcholine. Heptanol, an un
coupler of gap junctional communication, inhibited acetylcholine responses
in norepinephrine-constricted aortas from nonpregnant rats but greatly impa
ired acetylcholine relaxation in aortas from pregnant rats. Heptanol also i
nhibited in both groups acetylcholine responses in vessels constricted with
KCl, only minimally affected acetylcholine relaxation in arteries constric
ted with norepinephrine + L-NMMA, and did not change sodium nitroprusside-i
nduced relaxation. Tetraethylammonium chloride induced greater contractions
in control aortas compared with aortas from pregnant rats. Increased conne
xin43 mRNA levels were found in the uterus and in the mesenteric, uterine,
and thoracic aortic arteries, but not in the heart and brain, from pregnant
rats. These results suggest that increased gap junctional communication, p
ossibly due to increased gap junction protein expression, may facilitate th
e effects of endothelium-derived relaxing factors, contributing to the augm
ented endothelium-dependent relaxation in arteries from pregnant rats.