Effect of KMD-3213, an alpha1A-adrenoceptor antagonist, on the prostatic urethral pressure and blood pressure in male decerebrate dogs.

BACKGROUND: KMD-3213 is an alpha1A-adrenoceptor-selective antagonist currently being developed for the treatment of urinary outlet obstruction in patients with benign prostatic hyperplasia. In the present study, the uroselectivity of KMD-3213 was evaluated and compared with that of prazosin and tamsulosin in a decerebrate dog model. METHODS: Intercollicular decerebration was carried out in male mongrel dogs under anesthesia. The inhibitory effects of intravenously and intraduodenally administered compounds on the increase in intraurethral pressure (IUP) induced by electrical stimulation of the hypogastric nerve were estimated. Systemic blood pressure was measured simultaneously. RESULTS: The alpha1-antagonists tested produced a dose-dependent inhibition of the induced IUP response and decreased mean blood pressure (MBP). The ID50 of KMD-3213, tamsulosin and prazosin for IUP (dose required to inhibit the increase in IUP by 50%) was 3.15, 1.73 and 11.8 microg/kg i.v., respectively, and the ED20 for the hypotensive effect (dose required to reduce MBP by 20%) was 8.03, 0.59 and 2.46 microg/kg i.v., respectively. The data indicate that uroselectivity (ED20/ID50) of KMD-3213 is 12- and 7.5-fold higher than that of prazosin and tamsulosin, respectively. When the drugs were administered intraduodenally, KMD-3213 was sufficiently absorbed from the digestive tract and continued to demonstrate at least 3.8-fold higher uroselectivity than tamsulosin. CONCLUSION: Based on these findings, KMD-3213 appears to be an effective orally active compound for decreasing urethral resistance during micturition that does not induce any negative cardiovascular effects in patients with benign prostatic hyperplasia.

KMD-3213, a uroselective and long-acting alpha(1a)-adrenoceptor antagonist, tested in a novel rat model.

KMD-3213, an alpha(1a)-adrenoceptor (AR) antagonist, is under development for the treatment of urinary outlet obstruction in patients with benign prostatic hypertrophy. In the present study, we developed a rat model to investigate simply the effects of alpha(1)-AR antagonists on the intraurethral pressure (IUP) response to phenylephrine. Using this model, inhibitory effects of both i.v. and intraduodenally administered KMD-3213 on the IUP response were evaluated and compared to those of other reference compounds, including prazosin and tamsulosin. In addition, the hypotensive effects of these compounds were estimated to evaluate uroselectivity. Intravenously administered alpha(1)-AR antagonists tested, including KMD-3213, potently inhibited the IUP response in a dose-dependent manner. Although the higher doses of those compounds almost completely inhibited the IUP response, yohimbine failed to inhibit the response. When the in vivo potencies of those compounds on IUP response were correlated with their affinities for the human or animal recombinant alpha(1)-AR subtypes, alpha(1a)-AR gave the best correlation. In this model, KMD-3213 had greater uroselectivity than any other compounds examined, by both i.v. and intraduodenal routes. Moreover, 12, 18, and 24 h after the oral administration of KMD-3213, a dose-dependent inhibition of the IUP response was found, whereas the effect of tamsulosin disappeared at 18 h after the oral administration. These data indicate that KMD-3213 is a highly uroselective alpha(1)-AR antagonist with a longer duration of action. In addition, this model is useful for not only estimation of uroselectivity but also some part of the administration, distribution, metabolism, and excretion of many compounds to discover uroselective compounds.

Effect of KMD-3213, an alpha 1a-adrenoceptor-selective antagonist, on the contractions of rabbit prostate and rabbit and rat aorta.

KMD-3213, (-)-(R)-1-(3-hydroxypropyl)-5-[2-[[2-[2-(2,2,2-trifluoroethoxy) phenoxy]ethyl]amino]propyl]indoline-7-carboxamide, a newly synthesized alpha 1-adrenoceptor antagonist, has been shown to have potent action toward, and to be selective for human cloned and native alpha 1-adrenoceptors. In the present study, we characterized the inhibitory effect of KMD-3213 on the phenylephrine (alpha 1-adrenoceptor-selective agonist)-induced contraction of rabbit prostate, rabbit thoracic aorta and rat thoracic aorta to functionally confirm the tissue selectivity of KMD-3213. The mean pA2 value for KMD-3213 for the inhibition of the rabbit prostatic contraction was 10.05, whereas the values for the rabbit and rat aortic contractions were 9.36 and 8.13, respectively. The order of mean pA2 values for the inhibition of the rabbit prostatic contraction was KMD-3213 > or = tamsulosin >> prazosin, whereas that for the rabbit and rat aortic contractions was tamsulosin > KMD-3213 > prazosin and tamsulosin > or = prazosin >> KMD-3213, respectively. KMD-3213 produced a sigmoidal inhibition curve for single-dose phenylephrine-induced contractions of rabbit prostate, whereas it produced a non-sigmoidal curve for that of rabbit aorta. KMD-3213 had no effect on isoproterenol-induced chronotropic action in guinea-pig atria, and 5-hydroxytryptamine-, histamine- and acetylcholine-mediated contractions of rabbit aorta. These results indicate that the potency of the inhibitory activity of KMD-3213 depends on the tissue subtype expression and that KMD-3213 preferentially antagonizes prostatic contraction.

[Measurement of superoxide dismutase activity in normal skin by electron spin resonance-spin trapping method].

Superoxide dismutase (SOD) activity in 20 skin specimens from healthy individuals measured by the electron spin resonance-spin trapping method was 7.08 U +/- 0.41 U/mg protein (mean +/- SE). This method may be useful in the determination of SOD, since it requires a shorter time (approx. 3 min) and a smaller amount of specimen (approx. 30 mg) than previously reported methods other than the EIA method.

Binding of heparin or dermatan sulfate to thrombin is essential for the sulfated polysaccharide-accelerated inhibition of thrombin by heparin cofactor II.

Heparin cofactor II (HC II) and thrombin were chemically modified with pyridoxal 5'-phosphate, and their effects on the inhibition of thrombin by HC II in the presence of heparin or dermatan sulfate were studied. The inhibition of thrombin by HC II was enhanced about 7000-fold in the presence of heparin or dermatan sulfate. However, this enhancement by heparin dwindled to 110- and 9.6-fold when the modified HC II and the modified thrombin, respectively, were substituted for native proteins. Essentially identical results were obtained from the experiments using dermatan sulfate. These results indicate that the binding of heparin or dermatan sulfate to both thrombin and HC II is required for the sulfated polysaccharide-dependent acceleration of the thrombin inhibition by HC II, and the binding to thrombin is more essential for the reaction.

Specificity of sulfated polysaccharides to accelerate the inhibition of activated protein C by protein C inhibitor.

The ability of various sulfated polysaccharides to activate protein C inhibitor (PCI) and the effect of molecular weight (Mr) and sulfur content of dextran sulfates were investigated. Besides dextran sulfate, highly sulfated polysaccharides such as chondroitin polysulfates 1 and 5, and pentosan polysulfate were more active than heparin in enhancing the activated protein C inhibition by PCI. The molecular weight and the sulfur content of dextran sulfate were critical for the second-order rate constant of the reaction and for the optimal concentration of the polysaccharide, respectively. These results suggest that the carboxyl groups of polysaccharides are not necessarily required, but some sulfate groups within polymers may play a critical role in the interaction with PCI.

Studies on membrane proteins involved in ribosome binding on the rough endoplasmic reticulum. Ribophorins have no ribosome-binding activity.

A membrane protein fraction showing affinity for ribosomes was isolated from rat liver microsomes (microsomal fractions) in association with ribosomes by treatment of the microsomes with Emulgen 913 and then solubilized from the ribosomes with sodium deoxycholate. This protein fraction was separated into two fractions, glycoproteins, including ribophorins I and II, and non-glycoproteins, virtually free from ribophorins I and II, on concanavalin A-Sepharose columns. The two fractions were each reconstituted into liposomes to determine their ribosome-binding activities. The specific binding activity of the non-glycoprotein fraction was approx. 2.3-fold higher than that of the glycoprotein fraction. The recovery of ribosome-binding capacity of the two fractions was about 85% of the total binding capacity of the material applied to a concanavalin A-Sepharose column, and about 90% of it was found in the non-glycoprotein fraction. The affinity constants of the ribosomes for the reconstituted liposomes were somewhat higher than those for stripped rough microsomes. The mode of ribosome binding to the reconstituted liposomes was very similar to that to the stripped rough microsomes, in its sensitivity to proteolytic enzymes and its strong inhibition by increasing KCl concentration. These results support the idea that ribosome binding to rat liver microsomes is not directly mediated by ribophorins I and II, but that another unidentified membrane protein(s) plays a role in ribosome binding.

Thrombin inhibitory activity of heparin cofactor II depends on the molecular weight and sulfate amount of dextran sulfate.

The effect of molecular weight and sulfate amount of sulfated polysaccharide on the thrombin inhibitory activity of heparin cofactor II was investigated by using various dextran sulfate fractions with different molecular weight and sulfur content. The activity of dextran sulfate fractions of each size increased as the sulfur content was increased from 9 to 18%, and the activity decreased in molecules below 10 kDa. The maximum second order rate constant of heparin cofactor II-thrombin reaction in the presence of the fractions of over-10 kDa and 18% sulfur was 2.7 X 10(8) M-1 min-1 that was almost same as in the presence of heparin or dermatan sulfate. On the other hand, dextran sulfate accelerated antithrombin III-thrombin reaction only about 40-fold less than heparin. These results indicate that a large molecular size and significant amount of sulfate groups are only essential in the acceleration of the thrombin inhibitory activity of heparin cofactor II, whereas a specific sequence of heparin is required to that of antithrombin III.

Studies on the purification and characteristics of histidine-rich glycoprotein.

HRG demonstrated a high affinity for heparin and could thus participate in the inhibition of the clotting mechanism. HRG had inhibitory effects on DS as well, as was observed from assaying HC II activity. This investigation will be continued to clarify the role of HRG, HC II, AT III, and heparin in the prevention of thrombi formation.

Purification and biological property of heparin cofactor II: activation of heparin cofactor II and antithrombin III by dextran sulfate and various glycosaminoglycans.

Heparin cofactor II (HC II) has been purified from human plasma by a modification of the method described by Tollefsen et al. (J. Biol. Chem., 257, 2162, 1982) and abilities of dextran sulfate and various glycosaminoglycans to activate the antithrombin activities of HC II and antithrombin III (AT III) were studied. By the purification method described here, highly purified HC II with the same specific activity as reported by Tollefsen et al. was obtained with a higher yield and in a shorter purification time. Heparin, dextran sulfate and chondroitin polysulfates 1 and 5 activated both HC II and AT III, while dermatan sulfate activated only HC II. Dextran sulfate was almost as active as heparin in the activation of HC II and AT III, indicating that in the interactions of heparin with HC II and AT III, sulfate groups of heparin are more important than carboxyl groups. When mixed with thrombin in the presence of dermatan sulfate, normal human plasma showed antithrombin activity which was not due to AT III but to HC II only. HC II did not inhibit factor Xa or plasmin in the presence of any glycosaminoglycans or dextran sulfate, suggesting that HC II would be a specific inhibitor of thrombin.