Study of SR 142801, a new potent non-peptide NK3 receptor antagonist on cardiovascular responses in conscious guinea-pig.

1. The cardiovascular responses to intravenous (i.v.) injection of natural tachykinins, substance P (SP), neurokinin A (NKA), neurokinin B (NKB) and selective tachykinin (NK) receptor agonists, [Sar9, Met(O2)11]SP, [beta Ala8]NKA(4-10), [MePhe7]NKB and senktide were assessed in conscious, freely moving, guinea-pigs. 2. SP and [Sar9, Met(O2)11]SP (1-1000 pmol kg-1) induced dose-dependent decreases in mean arterial blood pressure (MAP) accompanied by increases in heart rate (HR). NKA evoked only weak hypotensive effects at high doses (3000 pmol kg-1) whereas [beta Ala8]NKA(4-10) (1-3000 pmol kg-1) had no effects. By contrast, NKB [MePhe7]NKB (1-10,000 pmol kg-1) and senktide (1-1000 pmol kg-1), produced dose-related hypertensive effects with the following rank order of potency: senktide > [MePhe7]NKB > NKB. Bradycardia occurred simultaneously with the increases in arterial pressure. 3. The pressor response to intravenous injection of senktide (300 pmol kg-1) was partially reduced by pretreatment with prazosin (0.71 mumol kg-1), or clonidine (0.38 mumol kg-1) and was completely inhibited by the combination of the two compounds. Atropine (1.5 mumol kg-1) suppressed the decrease in HR induced by senktide without altering the blood pressure response. These findings suggest that the blood pressure response to senktide is an indirect effect mediated by noradrenaline released from sympathetic nerve endings, whereas the bradycardia is of vagal reflex origin. 4. SR 142801, ((S)-(N)-(1-(3-(1-benzoyl-3-(3,4-dichlorophenyl) piperidin-3-yl) propyl)-4-phenyl-piperidin-4-yl)-N-methylacetamide), a potent and specific non-peptide NK3 receptor antagonist dose-dependently (0.46-4.6 mumol kg-1, i.v.; 4.6-46 mumol kg-1, p.o.) inhibited the cardiovascular effects of senktide and displayed a long-lasting inhibitory effect after oral administration. By contrast, SR 142806 (4.6 mumol kg-1, i.v.), the (R)-enantiomer of SR 142801 had no effect on the responses to senktide. SR 142801 at a high dose (15 mumol kg-1, i.v.) was inactive toward the [Sar9, Met(O2)11]SP-induced hypotension. 5. SR 142801 did not modify MAP in conscious guinea-pigs both after i.v. (4.6 and 15 mumol kg-1) and oral (46 and 150 mumol kg-1) administration, showing a lack of agonistic properties. However, a slight reduction in HR was observed only after i.v. injection. 6. In conclusion, these results show evident differences in the functional role of tachykinin receptors in the peripheral control of the cardiovascular system. Furthermore, a clear pressor effect of senktide, which was selectively blocked by SR 142801, was observed in conscious guinea-pigs. Hence, this antagonist appears suitable for investigating the functional role of NK3 receptors.

A pharmacodynamic study of SR 47436, a selective AT1 receptor antagonist, on blood pressure in conscious cynomolgus monkeys.

1. Conscious normotensive cynomolgus monkeys were chronically instrumented for the measurement of arterial blood pressure and heart rate to investigate the relationships between the plasma concentration, suppression of the pressor response to angiotensin II (AII), compensatory increase in plasma AII, and hypotensive effect obtained after a single oral dose of SR 47436, a potent and specific nonpeptide AT1 receptor antagonist. As blood sampling could influence the hypotensive effect of SR 47436 through activation of the renin angiotensin system (RAS), drug effects were studied in groups of animals with or without blood samplings. 2. SR 47436 at 10 mg kg-1 induced a hypotensive effect which was not greater following a second dose of 30 mg kg-1, indicating that a maximal hypotensive effect had already been obtained. 3. A single oral dose of SR 47436 (10 mg kg-1) caused a sustained hypotension and a marked inhibition of the AII-induced pressor response, lasting for up to 28 h. These effects of SR 47436 are consistent with good oral bioavailability and a slow elimination of the drug (t 1/2 approximately 20 h), and were accompanied by a sustained increase in plasma AII concentration. Taken together, both the hypotensive response and the compensatory increase in AII indicated that vascular and juxtaglomerular AII receptors were blocked. 4. Although a fair correlation between individual plasma drug concentrations and inhibition of AII-induced pressor response was observed, neither the hypotensive effect nor the compensatory increase in AII correlated with the plasma drug levels. 5. Basal arterial pressure and AII-induced pressor response were not affected by blood samplings. 6. These results suggest that SR 47436 is an effective and long lasting AT1 receptor antagonist with a potent hypotensive action in normotensive cynomolgus monkeys. It may be an efficacious blocker of the RAS in man and suitable for once-a-day dosing.

HLA compatibility for patients with thalassemia: implications for bone marrow transplantation.

In order to evaluate the possibility of a patient with thalassemia finding an HLA-identical sibling donor, we performed an analysis of HLA antigens in families of thalassemic patients. The pattern distribution was not significantly different from the expected ratio 25:50:25. When the siblings were subdivided according to the age of the patients (under or over 5 years), the above pattern remained unmodified for both the age groups. The average size of the 129 thalassemic families was 2.4. Thus, taking into account that thalassemic patients have an average of 1.4 siblings and that the HLA genotype distribution is expected as such, HLA-matched siblings are available for 33% of the patients. Because an additional 8.5% of the patients were found HLA-phenotypically identical to one parent, the chance for a patient with thalassemia to find a suitable donor for bone marrow transplantation would be increased to 41.5%. Our preliminary data cannot be extrapolated to the overall Italian thalassemic population; however, it can be inferred that for a patient with thalassemia, the chance of finding a suitable donor for bone marrow transplantation is not reduced.