Vaso-active factors in pregnancy

Abstract

Pregnancy results in profound physiological changes in the cardiovascular system, yet these changes are completely reversible. It is apparent that vaso-active factors, some as yet probably unidentified, which act as humoral or local autocrine or paracrine regulators of vasular resistance, play a major role in these cardio-vascular changes. This role may be heightened in pregnancy when there has to be a large increase in blood flow to the uterus and placenta while maintaining adequate flow to other vascular beds. Our knowledge of the mechanisms of action of these vaso-active factors and their interactions with each other still remains incomplete. Alterations in synthesis and action of these vaso-active factors may occur in pregnancies associated with pregnancy-induced hypertension, pre-eclampsia or intra-uterine growth retardation. Investigation of such alterations may help to elucidate the roles of vaso-active factors in both normal and pathological situations. The gestational hormones oestrogen and progesterone, are obviously prime candidates as overall regulators of the cardiovascular changes of pregnancy and as agents which alter the synthesis or action of other vaso-active factors. Currently, much attention is being focused on the role of local autocrine or paracrine vaso-active factors which may be produced by the endothelium or by the underlying vascular smooth muscle cells and alterations in their production or action in the hyptertensive disorders of pregnancy. The endothelium forms the largest endocrine organ within the body and so its importance in the mediation of vascular events should not be under-estimated. The principal objective of this review is to examine the roles of these many autocrine and paracrine vaso-active factors during pregnancy and their relation with the overall regulation of the vascular system. Changes which may occur and be involved in the aetiology of pre-eclampsia and growth retardation will also be examined.

Plasma From Normal Pregnant Women Alters the Reactivity of Rabbit Aortic Smooth Muscle With Functional Endothelium

“…The nature of the agent(s) remains speculative. Likely agents include the vasodilators prostacyclin and endothelium derived relaxing factors which are released in larger amounts in pregnancy (Friedman 1988;Ahokas et al 1991;Myatt 1992), and the reproductive hormones, oestrogens and progesterone (Rosenfeld & Jackson 1984;McLaughlin et al 1985;Naden & Rosenfeld 1985). Prostacyclin and endothelium derived relaxing factor (EDRF) have short lifespans and are known to function as paracrine agents rather than hormones (Friedman 1988;Pinto et al 1991).…”

Dietary calcium, magnesium, and phosphorus intakes and risk of stroke in Chinese adults

“…Decreased dietary calcium may induce calcium depletion from all membrane storage sites, leading to instability of the vascular smooth muscle cell membrane 35 , which may trigger vasoconstriction and, possibly, elevated blood pressures and stroke. In addition to the possible direct action on smooth muscle cell contraction, calcium may also have indirect effects by modifying the responsiveness to or regulating the synthesis of vasoactive mediators, including angiotensin II and nitric oxide 36 . Kawasaki et al 37 discovered that vascular sensitivity to angiotensin II decreased evidently after the supplementation of calcium.…”