Odd S. Steinsland

Increased Nitric Oxide Synthase Activity and Expression in the Human Uterine Artery During Pregnancy

Evidence exists that NO plays a role in the vasodilation that occurs during pregnancy. The purpose of the present study was to determine whether the role of NO is associated with an increase in the activity and protein expression of NO synthase (NOS) in the human uterine artery. Uterine arteries were obtained from pregnant patients (P arteries) and nonpregnant patients (NP arteries). NOS activity was estimated with the l-[3H]-arginine–to–l-[3H]-citrulline conversion method and on the basis of changes in tissue levels of cGMP. Western immunoblotting and immunohistochemistry were used to assess NOS protein expression. Ca2+-dependent NOS activity was 8 times greater (P <0.01) in P than in NP arteries. Although most of this pregnancy-induced increase in NOS activity was Ca2+ dependent (64%), a considerable portion was Ca2+ independent. Expressions of endothelial NOS (eNOS) and neuronal NOS, but not inducible NOS, were demonstrated in P and NP arteries. The eNOS was located in the endothelium and stained with a qualitative order of P arteries>NP arteries (follicular)>NP arteries (luteal). The neuronal NOS was located in the adventitia of P and NP arteries. Basal NO-dependent and bradykinin-stimulated levels of cGMP were higher (P <0.05) in P than in NP arteries. These results indicate that an upregulation of eNOS protein expression could account for the increased NO synthesis/release in the human uterine artery during pregnancy.

Increased vascular response to adrenergic stimulation in rats exposed to cadmium

Adult female rats were injected ip with a low total dose (1–2.25 mg/kg) or a high total dose (7.5 mg/kg) of cadmium, as cadmium chloride with cysteine, given in divided doses spaced over 1–3 wk. At 1–4 wk after administration of high doses of cadmium, anesthetized rats were less responsive to the pressor effect of norepinephrine (1.0–10.0 μg/kg, iv) than were controls. This type of effect has been described previously by other investigators and was not explored further in this study. In contrast to the results in high‐cadmium animals, anesthetized rats of the low‐cadmium group, tested 1–4 wk after exposure, were more sensitive to the pressor effects of norepinephrine (0.1–10.0 μg/kg, iv) than were controls. This increase in sensitivity was no longer apparent in animals tested 16–26 wk later. Neither basal blood pressure in anesthetized animals nor systolic pressure in conscious animals of the low‐cadmium series was different from the corresponding value in controls. Aortic rings isolated from low‐cadmium ...

The effects of cadmium on adrenergic neurotransmission invitro

Abstract The effect of cadmium on the response of isolated perfused rabbit ear arteries to nerve stimulation and norepinephrine administration was examined. Cadmium in concentrations of .075–.25μM caused enhancement of the pressor responses to nerve stimulation, but higher concentrations caused inhibition of the response. The pressor response to norepinephrine was also inhibited by cadmium, but required a 100x higher concentration than that needed for inhibition of the response to nerve stimulation. The dual effect of cadmium on the response to nerve stimulation suggests a plausible explanation for the conflicting reports in the literature regarding the blood pressure effects of cadmium exposure. The enhancement by low concentrations of cadmium of the response to nerve stimulation provides a possible mechanism for cadmium-induced hypertension.

Inhibition of cytomegalovirus replication by smooth-muscle relaxing agents.

Abstract The effect of the smooth-muscle relaxing agents, papaverine, sodium nitroprusside, and verapamil, on the replication of human cytomegalovirus (CMV) was investigated. At a concentration of 100 μM, infectious yields of CMV were reduced by 1.23 to 5.72 log10 by these drugs (papaverine, 5.72 log10; nitroprusside, 1.85 log10; verapamil, 1.23 log10). The ED50 for papaverine was found to be somewhat less than 1 μM, a concentration which appears to be within the range achieved clinically. Papaverine did not irreversibly modify treated cells to a virus-resistant state since treatment of cells with papaverine from 24 hr before until immediately prior to CMV infection did not significantly reduce CMV yields. Replication of CMV was most sensitive to inhibition when papaverine was added at or before 6 hr after CMV infection. Addition of papaverine at later times resulted in a substantial reduction of the inhibitory effect on virus yields, suggesting that the phase of CMV replication sensitive to papaverine inhibition occurred early in the replication cycle. These results, particularly in light of the potency of papaverine, indicate that some smooth-muscle relaxing agents have significant antiviral activity toward the replication of CMV.

A role for nitric oxide in endotoxin-induced depletion of the peripheral catecholamine stores.

Endotoxemia is associated with increased sympathetic nerve activity and depletion of norepinephrine (NE) and epinephrine (EPI) contents in the adrenal gland and in sympathetically innervated tissues. Endotoxin (bacterial lipopolysacchride [LPS]) causes an increased production of nitric oxide (NO) by inducing nitric oxide synthase (iNOS) expression in various tissues. This increased production of NO contributes significantly to the hypotension associated with endotoxemia. At high concentrations, NO also can act as a neurotoxin. In this study we tested the hypothesis that increased production of NO is involved in depletion of catecholamine content in various tissues from rats treated with a nonlethal dose of LPS. Catecholamine content was measured by high-performance liquid chromatography with electrochemical detection (HPLC-EC) and NOS activity was measured by the 3H-I-arginine to 3H-I-citrulline conversion method. The NE content was decreased in rat adrenal gland, lung, spleen, tail artery, and aorta after LPS. The maximal decrease was at 24 h and returned to control levels at 6 days (144 h). There was no depletion of the NE content in the heart. The EPI content in the adrenal gland was greatly depleted (91%) from 12 to 72 h after LPS. LPS increased the NOS activity in all tissues examined. The time course for NOS activity showed an increase at 3 h, a further increase at 6 h, and a return to control level at 48 h after LPS. The increase in NOS activity occurred before maximal catecholamine depletion. Aminoguanidine, a relatively selective iNOS inhibitor, completely prevented NE depletion in all tissues and partially prevented adrenal EPI depletion induced by LPS. These results are consistent with the hypothesis that LPS-induced production of NO plays a role in depletion of tissue NE and EPI.

Pregnancy: Increased effect of verapamil in human uterine arteries

The effect of verapamil on the contractile response to norepinephrine in isolated, suffused uterine arteries from pregnant and nonpregnant humans was investigated. The arteries, obtained after hysterectomy, were dissected free from surrounding tissue and arterial rings were prepared and mounted in tissue chambers filled with Krebs-bicarbonate solution. Isometric tension was recorded. There was no significant difference between arteries from pregnant patients and arteries from nonpregnant patients when maximal contractile response and sensitivity to norepinephrine were compared. At concentrations of 0.3 and 3 microM, verapamil attenuated the response to norepinephrine in uterine arteries from both pregnant and nonpregnant patients. However, verapamil was significantly more potent in blocking the response to norepinephrine in arteries from pregnant patients.

Similarities between cytomegalovirus-induced cell rounding and contraction of smooth muscle cells

Cytomegalovirus infection of human fibroblastic cell cultures resulted in rounding of the cells and a subsequent decrease in their size. Smooth muscle relaxing agents such as papaverine, hydralazine, diazoxide, nitroprusside and verapamil blocked these early cytopathogenic effects suggesting that cell rounding results from a contractile-like response involving an influx of calcium ions.

Isolated, perfused rabbit ear artery: a model for studying segmental vasoconstriction and dilatation.

Summary Severe increases in blood pressure (BP) are associated with a segmental pattern of constriction and dilatation in small arteries and arterioles, but the pathogenesis is poorly understood. We showed that the isolated, perfused rabbit ear artery typically develops segmental constriction and dilatation when intraluminal pressure is > 160–180 mm Hg during field stimulation of perivascular nerves (>6 Hz) or extra- or intraluminal infusions of norepinephrine (NE > 10-7 M) or phenylephrine (PE) (>5 x 10-7 M). Light, transmission, and scanning electron microscopy showed that the dilated vessel segments initially show endothelial injury with no smooth muscle lesions. After repeated or prolonged exposure to high intraluminal pressure, dilated segments manifest extensive and severe endothelial and smooth muscle damage. Dilated regions also became abnormally permeable to tracer particles (ferritin). Constricted segments did not show evidence of endothelial or smooth muscle injury or hyperpermeability. These changes, i.e., segmental vaso-constriction/dilatation, hyperpermeability, and vessel wall damage localized to dilated segments, are comparable to those that occur in small arteries and arterioles during severe hypertension. We discuss the potential usefulness of the isolated ear artery as a model for studying the pathogenesis and morphology of segmental vasocon-striction/dilatation.

Effects of cholera toxin on vasoconstriction and cyclic AMP content of the isolated rabbit ear artery

Abstract We have studied the effect of cholera toxin on the constrictor responses of the isolated, perfused rabbit ear artery to nerve stimulation and to norepinephrine infusion. We found that when we perfussed arteries with cholera toxin (1–9 μg/ml) for five minutes or longer, the toxin gradually inhibited the responses to intermittent stimulation of the adrenergic nerves and to brief infusion of norepinephrine. The constrictor responses began to decrease between one and two hours after we added cholera toxin, and the responses were still depressed after 24 hours. Cholera toxin inhibited both the rapid, initial phase and the slower, sustained phase of the biphasic response of the ear artery to nerve stimulation. Propranolol and indomethacin did not block the effect of cholera toxin on vasoconstriction. However, when we mixed the toxin with antitoxin or GM1 ganglioside, we prevented the inhibitory effect on vasoconstriction. Levels of adenosine 3′:5′-cyclic monophosphate (cyclic AMP) in arteries treated with cholera toxin were greater than levels of cyclic AMP in untreated arteries. The cyclic AMP content increased and the constrictor responses decreased with a similar time course after the arteries were exposed to the toxin. Thus an increase in cyclic AMP may be involved in the relaxation of vascular smooth muscle induced by cholera toxin.

Dopamine receptors: Structure-activity relationship of d-tubocurarine analogues

d-Tubocurarine (dTC) and d-tubocurine acted as antagonists of the dopamine-induced inhibition of adrenergic neurotransmission in the isolated, perfused rabbit ear artery. N-Methyl-dTC and O,O,N-trimethyl-dTC (metocurine) did not exhibit dopaminergic antagonist activity. dTC contains one tertiary (3 degrees) nitrogen and one quaternary (4 degrees) nitrogen and d-tubocurine contains two 3 degrees nitrogens; whereas, both N-methyl-dTC and O,O,N-trimethyl-dTC have two 4 degrees nitrogens. The results suggest that a dTC analogue (e.g., metocurine) which lacks a 3 degrees nitrogen should be considered for use in patients treated with dopamine.