Effects of tezosentan, a dual endothelin receptor antagonist, on the cardiovascular and renal systems of neonatal piglets

Repetitive urine and blood sampling in neonatal and weaned piglets for pharmacokinetic and pharmacodynamic modelling in drug discovery: a pilot study

Piglets are considered to be suitable animal models for predicting the pharmacokinetics and pharmacodynamics (PK/PD) of test drugs for potential use in the paediatric population. Such PK/PD studies require multiple blood and urine samplings. The goal of the present study was to determine a suitable blood collection strategy applicable in the youngest age categories of six days, four weeks and eight weeks of age, as well as a urine collection technique for male piglets in the same age categories. Blood was collected either by a surgically-placed jugular vein catheter (six days old [ n = 4] and four weeks old [ n = 2] piglets) or by direct venepuncture of the jugular vein (four weeks old [ n = 2] and eight weeks old [ n = 4] piglets). A non-invasive method for total volume urine collection in male piglets was also developed using a urine pouch. No specific complications were encountered during anaesthesia or surgery for jugular catheter placement. After a 24 h recovery period, urine and blood were easily collected without technical complications. One piglet was humanely killed at week 2 because of septicaemia. Histological analysis of both veins in all four piglets revealed negligible damage to the blood vessel wall. In conclusion, the presented techniques for blood (jugular catheter and direct venepuncture) and urine collection (pouches) are suitable for PK/PD studies in piglets.

Tezosentan decreases pulmonary artery pressure and improves survival rate in an animal model of meconium aspiration

Acute pulmonary arterial hypertension in acute lung injury aggravates the clinical course and complicates treatment. Increased release and turnover of endogenous endothelin-1 is known to be a major determinant in the pathophysiology of pulmonary arterial hypertension of various etiologies. We tested whether intravenous tezosentan, a dual endothelin receptor antagonist, reduced pulmonary artery pressure in a pig model of acute lung injury induced by meconium aspiration. Acute pulmonary arterial hypertension was induced in 12 anesthetized and instrumented pigs by instillation of human pooled meconium in a 20% solution. Hemodynamic and gas exchange parameters were recorded every 30 min. Six animals received tezosentan 5 mg/kg after 0 and 90 min; six animals served as controls. Tezosentan led to a decrease of mean pulmonary artery pressure (PAP) from 33.4 +/- 4.0 mm Hg to 24.7 +/- 2.1 mm Hg and pulmonary vascular resistance (PVR) from 7.8 +/- 1.4 mm Hg.L(-1).min.m2 to 5.2 +/- 0.7 mm Hg.L(-1).min.m2. All animals treated with tezosentan survived, whereas in the control group four out of six animals died. Tezosentan improved survival and decreased pulmonary artery pressure in a porcine model of acute pulmonary arterial hypertension after meconium aspiration. Tezosentan has the potential for effective pharmacological treatment of pulmonary arterial hypertension following acute lung injury.

Bacterially synthesized folate and supplemental folic acid are absorbed across the large intestine of piglets

A large pool of folate exists in the large intestine of humans. Preliminary evidence, primarily in vitro, suggests that this folate may be bioavailable. The purpose of this study was to test the hypothesis that supplemental folic acid and bacterially synthesized folate are absorbed across the large intestine of piglets. The pig was used as an animal model because it resembles the human in terms of folate absorption, at least in the small intestine. A tracer of [3H]-folic acid or [3H]-para-aminobenzoic acid ([3H]-PABA), a precursor of bacterially synthesized folate, was injected into the cecum of 11-day-old piglets. Feces and urine were collected for 3 days. Thereafter, piglets were killed, and livers and kidneys harvested. [3H]-Folate was isolated from biological samples by affinity chromatography using immobilized milk folate binding proteins and counted using a scintillation counter. In piglets injected with [3H]-folic acid, the feces, liver, urine and kidneys accounted for 82.1%, 12.3%, 3.9% and 1.7% of recovered [3H]-folate, respectively. In piglets injected with [3H]-PABA, the amount of recovered bacterially synthesized folate in the feces, liver and urine was 85.1%, 0.4% and 14.6%, respectively. Twenty-three percent and 13% of tritium were recovered in samples examined (liver, kidney, fecal and urine) from piglets injected with [3H]-folic acid and [3H]-PABA, respectively. Using our estimates of [3H]-folic acid absorption and the total and percent monoglutamyl folate content of piglet feces, we predict that at least 18% of the dietary folate requirement for the piglet could be met by folate absorption across the large intestine.

Tezosentan, a combined parenteral endothelin receptor antagonist, produces pulmonary vasodilation in lambs with acute and chronic pulmonary hypertension

OBJECTIVE

To investigate the hemodynamic effects of tezosentan in the intact lamb both at rest and during acute and chronic pulmonary hypertension.

DESIGN

Prospective, randomized experimental study.

SETTING

University-based research laboratory.

SUBJECTS

Lambs with and without pulmonary hypertension.

INTERVENTIONS

Six newborn lambs were instrumented to measure vascular pressures and left pulmonary blood flow. The hemodynamic effects of tezosentan (0.5, 1.0, 5.0 mg/kg, intravenously) were studied at rest and during U46619-induced pulmonary hypertension. Following in utero placement of an aortopulmonary vascular graft, nine additional lambs with increased pulmonary blood flow and chronic pulmonary hypertension (shunt) were also studied at 1 wk (n = 5) and 8 wks (n = 4) of age.

MEASUREMENTS AND MAIN RESULTS

At rest, tezosentan had no significant effect on any of the variables. During acute U46619-induced pulmonary hypertension, tezosentan caused a dose-dependent decrease in pulmonary arterial pressure (from 5.9% +/- 4.7 to 16.0% +/- 10.7; p < .05) and pulmonary vascular resistance (from 6.2% +/- 8.0 to 21% +/- 8.8; p < .05). Mean systemic arterial pressure was unchanged. In 1- and 8-wk-old shunt lambs with increased pulmonary blood flow, tezosentan (1 mg/kg) produced potent nonselective pulmonary vasodilation.

CONCLUSIONS

Tezosentan, a combined endothelin receptor antagonist optimized for parenteral use, induces potent selective pulmonary vasodilation during acute U46619-induced pulmonary hypertension and potent nonselective vasodilation in chronic pulmonary hypertension secondary to increased pulmonary blood flow. In general, the hemodynamic effects of bolus doses of tezosentan occurred within 60 secs of administration and lasted approximately 5-10 mins. The hemodynamic profile of intravenous tezosentan may make it a useful adjunct therapy for acute pulmonary hypertensive disorders and warrants further study.