Blocking effects of OPC-21268 and OPC-31260 (vasopressin V1- and V2-receptor antagonists) on vasopressin-induced constrictions in isolated, perfused dog femoral arteries

Effects of the non-peptide inhibitor OPC-21268 on oxytocin and vasopressin stimulation of rat and human myometrium

OPC-21268 (1-[-1-[4-(3-acetylaminopropoxy)benzoyl]-piperidyl]-3,4- dihydro-2(1H)-quinolinone), a non-peptide vasopressin V1 receptor antagonist, inhibited oxytocin- and vasopressin-induced contractions of myometrial strips from rats and from full-term pregnant women. Administered intravenously in rats the drug also inhibited uterine contractions caused by infusion of oxytocin. When incubated with purified plasma membranes from rat or human myometrial tissue, OPC-21268 inhibited the specific receptor binding of tritiated oxytocin and vasopressin in a dose-dependent and reversible way.

OPC-21268 antagonizes arginine vasopressin-induced vasoconstrictor response in the spinally-anesthetized dog

We studied the antagonistic actions of OPC-21268 (1-(1-[4-(3-acetylaminopropoxy)-benzoyl]-4-piperidyl)-3,4-dihydro- 2(1H)-quinolinone) on the arginine vasopressin (AVP)-induced vasoconstrictor response in the spinally-anesthetized dog. OPC-21268 at doses of 0.3, 1.0 and 3.0 mg/kg, i.v. produced a rightward parallel shift of the dose-response curves for AVP in a dose-dependent manner. The doses of OPC-21268 were similar to those that inhibited the AVP-induced vasoconstrictor response in the rat. This observation suggests that OPC-21268 acts as a V1-AVP-receptor antagonist in peripheral resistance vessels in dogs as well as in rats.

Human internal mammary artery responses to non-peptide vasopressin antagonists

1. OPC-21268 and OPC-31260 are newly developed orally active non-peptide vasopressin (AVP) V1 and V2 receptor antagonists, respectively. The effects of the two compounds on human vessels have not been studied. 2. The effects of the two compounds on AVP-induced contraction of human internal mammary arteries (IMA) were investigated. Their effects were compared with the peptide V1 and V2 antagonists d(CH2)5Sar7AVP (SAVP) and d(CH2)5D-Ileu2Ileu4AVP (Ileu2Ileu4AVP), respectively. 3. The V1 antagonist OPC-21268 failed to antagonize AVP-induced contraction at low concentrations and potentiated the contraction at higher concentration (3 x 10(-7) mol/L, P < 0.05). It also caused a mild direct contractile effect on IMA. In contrast, the peptide V1 antagonist SAVP potently inhibited the AVP-induced contraction, indicating that functionally constrictor V1 receptors exist in IMA. Both the nonpeptide and peptide V2 antagonists OPC-31260 (3 x 10(-6) mol/L) and Ileu2Ileu4AVP significantly antagonized the AVP-induced contraction (P < 0.01). 4. The AVP-induced contraction was reversed by high concentrations of OPC-31260 (10(-6) mol/L-3 x 10(-5) mol/L) but not by OPC-21268 (up to 3 x 10(-5) mol/L). 5. These studies indicate that, in human IMA, OPC-21268 is a partial V1 receptor agonist with no V1 receptor antagonist activity, while OPC-31260 is a V1 receptor antagonist. The results also indicate that Ileu2Ileu4AVP may be a V1 receptor antagonist in humans.

Potent antagonistic action of OPC-31260, a vasopressin V2 receptor antagonist, on [Arg8]vasopressin-induced vasoconstriction in isolated simian femoral arteries

Using a perfusion technique with isolated vessels, we investigated the effect of OPC-21268 (a selective V1 receptor antagonist) and OPC-31260 (a V2 receptor antagonist) on arginine vasopressin (AVP)- or norepinephrine (NE)-induced vasoconstrictions of isolated simian femoral arteries. The dose-response curve for AVP was shifted to the right in parallel by OPC-31260 but not by OPC-21268. Neither antagonist significantly modified the NE-induced vasoconstriction. On the basis of these results, there are functionally constrictory vasopressin V2 receptors but no V1 receptors in isolated simian femoral arteries.