Changes in coronary resistance related to the stages of the female life cycle.
BACKGROUND
Estrogen is known to dilate the coronary vascular system mainly through nitric oxide (NO) release. However, it has not been determined whether or not this effect occurs equally throughout all stages of the female life cycle. We examined the changes in coronary flow properties in adolescent, adult and ovariectomized (OVX) female rats using the endothelial NO synthetase blocker, L-N (omega) nitroarginine (L-NNA).


RESULTS
Female rats were divided into 3 groups: adolescent (13 weeks, n=6), adult (19 weeks, n=8) and OVX (20 weeks, n=7, 12 weeks after oophorectomy). Coronary effluent was measured using the Langendorff non-working heart model before and 15 min after the use of L-NNA. In OVX rats, coronary effluent was significantly decreased in comparison with adolescent and adult rats (adolescent vs OVX: p<0.001; adult vs OVX: p<0.05). After treatment with L-NNA, coronary effluent was significantly higher in the adolescent group compared with the adult and OVX groups (adolescent vs adult: p<0.01; adolescent vs OVX: p<0.0005).


CONCLUSIONS
Oophorectomy brought about an increase in coronary vascular resistance. L-NNA exacerbated coronary vascular resistance in relation to maturation. It is suggested that the effect of estrogen on vascular dilatation in adolescents is largely dependent on a non-NO pathway, whereas adults are largely dependent on an NO pathway.
School of Medicine, University of Tsukuba, Tenoudai, Japan.
Shinji
S
Fukuhara
Shonosuke
S
Matsushita
Yuzuru
Y
Sakakibara
D000375:Aging; D000818:Animals; D003331:Coronary Vessels / Q000502:physiology*; D004967:Estrogens / Q000502:physiology; D005260:Female; D008018:Life Cycle Stages; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000502:physiology; D019335:Nitroarginine / Q000494:pharmacology; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000187:drug effects; D012737:Sex Factors; D014655:Vascular Resistance / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects
D004967:Estrogens; D019335:Nitroarginine; D052250:Nitric Oxide Synthase Type III