Hemodynamic effects of calibrated stenosis of the superior mesenteric artery in conscious rats with portal vein stenosis

Functional symmetry of the aortic baroreflex in female spontaneously hypertensive rats

BACKGROUND

Altered baroreflex function is well documented in hypertension; however, the female sex remains far less studied compared with males. We have previously demonstrated a left-sided dominance in the expression of aortic baroreflex function in male spontaneously hypertensive rats (SHRs) and normotensive rats of either sex. If lateralization in aortic baroreflex function extends to hypertensive female rats remains undetermined. This study, therefore, assessed the contribution of left and right aortic baroreceptor afferents to baroreflex modulation in female SHRs.

METHOD

Anesthetized female SHRs (total n  = 9) were prepared for left, right and bilateral aortic depressor nerve (ADN) stimulation (1-40 Hz, 0.2 ms, 0.4 mA for 20 s) and measurement of reflex mean arterial pressure (MAP), heart rate (HR), mesenteric vascular resistance (MVR) and femoral vascular resistance (FVR). All rats were also matched for the diestrus phase of the estrus cycle.

RESULTS

Reflex (%) reductions in MAP, HR, MVR and FVR were comparable for both left-sided and right-sided stimulation. Bilateral stimulation evoked slightly larger ( P  = 0.03) reductions in MVR compared with right-sided stimulation; however, all other reflex hemodynamic measures were similar to both left-sided and right-sided stimulation.

CONCLUSION

These data show that female SHRs, unlike male SHRs, express similar central integration of left versus right aortic baroreceptor afferent input and thus show no laterization in the aortic baroreflex during hypertension. Marginal increases in mesenteric vasodilation following bilateral activation of the aortic baroreceptor afferents drive no superior depressor responses beyond that of the unilateral stimulation. Clinically, unilateral targeting of the left or right aortic baroreceptor afferents may provide adequate reductions in blood pressure in female hypertensive patients.

Differential central integration of left versus right baroreceptor afferent input in spontaneously hypertensive rats

BACKGROUND

The blood pressure (BP) regulatory impact of the arterial baroreflex has been well established in health and disease. Under normotensive conditions, we have previously demonstrated functional differences in the central processing of the left versus right aortic baroreceptor afferent input. However, it is unknown if lateralization in aortic baroreflex function remains evident during hypertension.

METHOD

We therefore, investigated the effects of laterality on the expression of baroreflex-driven cardiovascular reflexes in a genetic model of essential hypertension, the spontaneously hypertensive rat (SHR). Anesthetized male SHRs (total n  = 9) were instrumented for left, right, and bilateral aortic depressor nerve (ADN) stimulation (1-40 Hz, 0.2 ms, and 0.4 mA for 20 s) and measurement of mean arterial pressure (MAP), heart rate (HR), mesenteric vascular resistance (MVR), and femoral vascular resistance (FVR).

RESULTS

Left right, and bilateral ADN stimulation evoked frequency-dependent decreases in MAP, HR, MVR, and FVR. Left and bilateral ADN stimulation evoked greater reflex reductions in MAP, HR, MVR, and FVR compared with right-sided stimulation. Reflex bradycardia to bilateral stimulation was larger relative to both left-sided and right-sided stimulation. Reflex depressor and vascular resistance responses to bilateral stimulation mimicked those of the left-sided stimulation. These data indicate a left-side dominance in the central integration of aortic baroreceptor afferent input. Furthermore, reflex summation due to bilateral stimulation is only evident on the reflex bradycardic response, and does not drive further reductions in BP, suggesting that reflex depressor responses in the SHRs are primarily driven by changes in vascular resistance.

CONCLUSION

Together, these results indicate that lateralization in aortic baroreflex function is not only evident under normotensive conditions but also extends to hypertensive conditions.

Type 2 diabetes mellitus as a risk factor for intestinal resection in patients with superior mesenteric vein thrombosis

BACKGROUND & AIMS

The most serious complication of acute mesenteric vein thrombosis (MVT) is acute intestinal ischaemia requiring intestinal resection or causing death. Risk factors for this complication are unknown. To identify risk factors for severe intestinal ischaemia leading to intestinal resection in patients with acute MVT.

METHODS

We retrospectively analysed consecutive patients seen between 2002 and 2012 with acute MVT in 2 specialized units. Patients with cirrhosis were excluded. We compared patients who required intestinal resection to patients who did not.

RESULTS

Among 57 patients, a local risk factor was identified in 14 (24%) patients, oral contraceptive use in 16 (29%), and at least one or more other systemic prothrombotic condition in 25 (44%). Five (9%) patients had diabetes mellitus (DM), 33 (58%) had overweight or obesity, 9 (18%) had hypertriglyceridemia and 10 (19%) had arterial hypertension. Eleven patients (19%) underwent intestinal resection. DM was significantly associated with intestinal resection (P = 0.02) while local factors or prothrombotic conditions were not. Computed tomography (CT) scans performed at diagnosis found that occlusion of second order radicles of the superior mesenteric vein was more frequently observed in patients who underwent intestinal resection (P = 0.009).

CONCLUSIONS

In acute MVT, patients with underlying DM have an increased risk of requiring intestinal resection. Neither local factors nor systemic prothrombotic conditions are associated with intestinal resection. When CT scan shows the preservation of second order radicles of the superior mesenteric vein, the risk of severe resection is low.

Haemodynamic effects of chronic octreotide and tetrandrine administration in portal hypertensive rats

Octreotide is an effective portal hypotensive drug in the control of variceal bleeding. Tetrandrine is a type of calcium channel blocker recently reported to reduce portal hypertension. The present study was undertaken to investigate the haemodynamic effects of octreotide and tetrandrine, alone and in combination, in portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation. Portal hypertensive rats were allocated into one of the four groups: vehicle group (saline, 0.5 mL/day), octreotide group (100 microg/kg per 12 h), tetrandrine group (20 mg/kg per 12 h), and octreotide (100 microg/kg per 12 h) plus tetrandrine (20mg/kg per 12 h) group. Tetrandrine or saline was administered by gavage, and octreotide by subcutaneous injection. The drug was given for 8 consecutive days, starting 1 day before ligation and continuing onwards. Haemodynamic parameters were measured thereafter, using the radioactive microsphere method. The portal venous pressure and portal tributary blood flow were significantly reduced, while portal territory and renal vascular resistances were significantly enhanced, by octreotide, tetrandrine, or octreotide plus tetrandrine in portal hypertensive rats, compared with the vehicle group. Our results showed that long-term administration of octreotide, tetrandrine, or octreotide plus tetrandrine led to portal hypotensive effects in portal hypertensive rats, but octreotide alone exerted better anti-hyperdynamic effects compared with tetrandrine alone. A combination of octreotide and tetrandrine offered no major beneficial anti-hyperdynamic effects compared with octreotide alone.

Effects of superior mesenteric artery stenosis on splanchnic and systemic hemodynamics in conscious rats with biliary cirrhosis

BACKGROUND/AIMS

Since portal tributary blood flow is increased in portal hypertension due to cirrhosis, a reduction in mesenteric arterial blood flow should decrease portal pressure.

METHODS

Calibrated stenosis of the superior mesenteric artery was performed in bile duct ligated rats, using a 22-gauge needle. Arterial stenosis was performed 4 weeks after bile duct ligation. Hemodynamic studies were performed in the 5th week following bile duct ligation in conscious rats.

RESULTS

At that time, no digestive tract alterations were observed. In rats with mesenteric arterial stenosis, portal pressure was 12.2 +/- 2.0 mmHg; this value was lower than in rats with cirrhosis without arterial stenosis (14.5 +/- 1.1 mmHg) but higher than normal rats (5.8 +/- 0.7 mmHg). In rats with cirrhosis with mesenteric arterial stenosis, portal tributary and mesenteric blood flows were lower than in rats with cirrhosis without arterial stenosis and not significantly different from normal rats. In rats with mesenteric stenosis, cardiac index was significantly lower than in rats with cirrhosis and not significantly different from normal rats.

CONCLUSION

This study shows that calibrated superior mesenteric arterial stenosis normalized portal tributary blood flow and reduced but did not normalize the degree of portal hypertension.