Synthetic atrial natriuretic factor is a specific dilator of noradrenaline and serotonin activated renal resistance vessels.

The action of a synthetic 'atrial natriuretic factor' (sANF) on induced tone in isolated rat renal resistance vessels (lumen diameter about 200 microns) was examined and compared with the effects of sANF on resistance vessels of similar size taken from the cerebral, mesenteric and femoral vasculature. Synthetic ANF caused a relaxation of the renal vessels when these were submaximally activated with noradrenaline or serotonin, but had no effect on the responses of the other vessels to these agonists. In contrast to previous reports concerning rabbit aortic vessels, methylene blue (which is thought to cause inhibition of guanyl cyclase) did not reduce the dilator response to sANF in the renal vessels.

Abnormal vascular function and morphology in pre-eclampsia: a study of isolated resistance vessels.

In order to obtain direct information about vascular changes associated with pre-eclampsia, the morphological and functional characteristics of isolated omental resistance vessels from 11 women with pre-eclampsia, 10 normotensive pregnant women and eight normotensive non-pregnant women were determined. In vessels from the women with pre-eclampsia, the ratio of media thickness to lumen diameter was increased, compared with that in vessels from the other two groups. The vessels from the women with pre-eclampsia had an increased responsiveness to angiotensin II and a decreased rate of relaxation, but only when compared with the vessels from the normotensive pregnant women.

Atrial natriuretic factor causes specific relaxation of rat renal arcuate arteries.

We have investigated the effect of a synthetic 'atrial natriuretic factor' (ANF) on induced tone in rat isolated renal arcuate arteries (lumen diameter ca. 250 microns), and compared this with the effects of synthetic ANF on resistance vessels of similar size taken from the mesenteric, femoral, cerebral and coronary vasculature. Synthetic ANF was found to cause relaxation of the renal vessels when these were sub-maximally activated with K+, noradrenaline or 5-hydroxytryptamine, but had no effect on the responses of the other vessels to these agonists.

Effect of ouabain on tone, membrane potential and sodium efflux compared with [3H]ouabain binding in rat resistance vessels.

To investigate the mechanism by which ouabain causes acute increase in peripheral resistance, the effect of ouabain on vessel tone, 22Na efflux and membrane potential has been compared with the binding of [3H]ouabain in rat isolated mesenteric resistance vessels (lumen diameter approximately 200 microns). Ouabain at concentrations between 1 X 10(-8) and 1 X 10(-3) M had no effect on the tone of resting vessels but caused potentiation of the tone of vessels which were submaximally contracted with noradrenaline. In the entire concentration range, these acute potentiating effects of ouabain on vessel tone correlated well with an acute inhibitory effect on 22Na efflux and with acute [3H]ouabain binding, consistent with the vasoconstrictor effect of ouabain being associated with inhibition of the Na-K pump.

Ouabain binding and Na+ content in resistance vessels and skeletal muscles of spontaneously hypertensive rats and K+-depleted rats.

The possible role of Na+ in the development of hypertension in rats was explored in measurements of intracellular Na+, 22Na efflux, and 3H-ouabain binding sites in resistance vessels and skeletal muscles. In resistance vessels obtained from 13-week-old spontaneously hypertensive rats (SHR) or age-matched Wistar-Kyoto rats (WKY), (Na)i, total or ouabain-resistant 22Na efflux, and the concentration of 3H-ouabain binding sites showed no significant differences. Soleus muscles obtained from 6-week-old and 13-week-old SHR contained 5 to 11% more 3H-ouabain binding sites than those of WKY.

Characteristics of resistance vessels in pre-eclampsia and normotensive pregnancy.

Isolated omental resistance vessels from women with pre-eclampsia had an increased media thickness/lumen diameter ratio compared to similar vessels from normotensive pregnant women. The active and passive tension length curves for the two groups of vessels were similar and like the classical tension length curve for skeletal muscles. The maximal media stress (force per media cross-section) was also similar; however, calculating in terms of equivalent pressure (on basis of Laplaces law) indicated that the vessels in vivo would have been able to contract against an increased blood pressure.

Intracellular sodium, membrane potential, and contractility of rat mesenteric small arteries.

We have investigated effects of altered extracellular sodium, intracellular sodium concentration, and membrane potential on the contractile responses of rat isolated mesenteric small arteries (internal diameter ca. 200 microns), when mounted as ring preparations on an isometric myograph. To avoid possible neural effects, all vessels were denervated in vitro using 6-hydroxydopamine.

Sodium metabolism in rat resistance vessels.

Using 22Na we have investigated the Na metabolism in rat mesenteric resistance vessels (internal diameter about 200 micron). The intracellular Na content was determined by washing the vessels at 0 degrees C in saline with Li substituted for Na, and was related to smooth muscle volume determined from measurements of media thickness and internal diameter using light microscopy. On this basis an internal Na concentration of 13.

Human and rat resistance vessels: a comparison of their morphological and pharmacological characteristics.

The morphology and pharmacology of isolated human omental and rat mesenterial resistance vessels of about 200 micron i.d. have been compared.

Functional and morphological properties of human omental resistance vessels.

We have examined the functional and morphological properties of arterial resistance vessels with lumen diameters about 200 micrometer from the human omentum. The vascular smooth muscle cells were circumferentially oriented and arranged in about 3 layers within the media. The cells, when held at a length where their contractile response was maximal, were 97 micrometer long and had a mean diameter of 3.

Morphological and mechanical properties of small mesenteric arteries and veins in spontaneously hypertensive rats.

Segments of small mesenteric arteries(approximately 150 micrometer lumen diameter) and of corresponding veins were taken from 5-month-old spontaneously hypertensive rats(SHR) AND FROM AGE MATCHED Wistar Kyoto (WKY) controls. The segments were mounted on a myograph which enabled their mechanical and morphological parameters to be investigated simultaneously. Compared with the WKY arteries the lumen diameter of the SHR arteries was smaller while the media thickness and active wall tension response were greater.

Effect of age on noradrenaline sensitivity of mesenteric resistance vessels in spontaneously hypertensive and Wistar-Kyoto rats.

1. We have compared the noradrenaline sensitivity of 150 micron arterial resistance vessels taken from a specific place in the mesenteric bed of spontaneously hypertensive (SH) rats and of control Wistar-Kyoto (WK) rats at three ages: 6 weeks, 12 weeks and 24 weeks. 2.

Direct evidence that the greater contractility of resistance vessels in spontaneously hypertensive rats is associated with a narrowed lumen, a thickened media, and an increased number of smooth muscle cell layers.

The mechanical and morphological properties of segments of certain precisely defined resistance vessels (approximately 150 micrometer lumen diameter) in the mesenteric bed of spontaneously hypertensive (SHR) and normotensive (WKY) rats have been compared in vitro under carefully controlled conditions and also after fixation. At a given transmural pressure, the relaxed SHR vessels (compared with the WKY vessels) would have had a 16% smaller lumen diameter (P less than 0.01) and a 49% thicker media (P less than 0.