Pressure-diameter curves of mesometrial arteries of guinea pigs demonstrate a non-muscular, oestrogen-inducible mechanism of lumen regulation

Abstract

Pressure-diameter curves were determined on mesometrial (uterine radial) arteries obtained from guinea pigs during different stages of ovarian cycle and pregnancy. In order to investigate changes in arterial diameter that are not caused by the vascular musculature, we studied excised arteries that were relaxed by papaverine (40 mg/l). The pressure-diameter curves were found to be shifted toward wider diameters when the arteries studied were obtained from pregnant, oestrous or oestrogen treated animals (oestradiol benzoate, 10 micrograms s.c.): the external diameter at 60 mm Hg transmural pressure on the 14th day of pregnancy exceeded the one during dioestrus by 50%. At term, there was a 7-fold increase. During oestrus and 24 h after oestrogen treatment the diameter was 30-40% wider than during dioestrus. Moreover, we found that the diameter measured on excised vessels in the presence of papaverine is the same as the one observed in situ. We conclude that the mesometrial arteries of guinea pigs possess a muscle-independent mechanism of lumen regulation. The mechanism operates in non-pregnant and pregnant animals. It may be induced by oestrogen and seems to be qualified for long-term lumen regulation during pregnancy. In contrast, dilation by smooth muscle relaxation appears to be of minor importance in mesometrial arteries.

Effect of Pregnancy and Sex Steroids on α1‐Adrenoceptor Mechanisms in the Guinea‐Pig Uterine Vascular Bed

“…The increase in vessel diameter of the extrinsic uterine arteries of the pregnant animals in the present study is in concert with that of previous reports (Bell & Brown 1971;Moll et al 1983;Moll & Gotz 1985). The increase in the transectional area of the different components in the vessel walls is considered to be the result of both cell proliferation (hyperplasia) and an increase in size of the individual cells (hypertrophy; Moll el al.…”

Uterine blood flow during the development and regression of the decidual cell reaction in ovariectomized, steroid-treated mice

“…The proportion of cardiac output perfusing the uterus of the ovariectomized, oestradiol-treated mouse in the present study (017 + 003%) is similar to that in non-pregnant rats (012 + 001%) (Ahokas et al, 1983). In the guinea-pig, it has been reported that uterine radial (mesometrial) artery diameter increased by 30-40% 24 h after subcutaneous injection of oestradiol (Moll & Götz, 1985) and a similar mechanism may operate in the mouse uterus. The present study also showed that oestradiol caused a significant increase in uterine blood flow on the day of maximal sensitivity to a decidual stimulus, although by 4 days later the uterus had lost this sensitivity to oestradiol.…”

Predominance of Local Over Systemic Factors in Uterine Arterial Remodeling During Pregnancy

“…Sex steroids, particularly estrogens, have been shown to cause significant uterine vascular growth in several species of rodents. For example, exogenous estradiol and estrus states in guinea pigs increased uterine small artery diameter by 30–40%, although it is not clear whether this is due to vasodilation or true growth 11. Estrogen also increased the size of ovarian and uterine veins, and of the uterine corpus in non-pregnant mice compared to controls 12, 30.…”

“…For example, intravascular pressure and shear stress each produce distinct effects on vascular structure, as do steroid hormones - particularly C18 and C19 sex steroids 11, 12. At this time, however, the molecular signals that mediate and coordinate the process of remodeling during pregnancy have not been described, and the physiological pathways through which changes are effected are not known.…”