Structure and Properties of fac-[Re(I)(CO)3(NTA)](2-) (NTA(3-) = Trianion of Nitrilotriacetic Acid) and fac-[Re(I)(CO)3(L)](n-) Analogues Useful for Assessing the Excellent Renal Clearance of the fac-[(99m)Tc(I)(CO)3(NTA)](2-) Diagnostic Renal Agent.

We previously identified two new agents based on the [(99m)Tc(V)O](3+) core with renal clearances in human volunteers 30% higher than that of the widely used clinical tracer (99m)Tc-MAG3 (MAG3(5-) = penta-anion of mercaptoacetyltriglycine). However, renal agents with even higher clearances are needed. More recently, we changed our focus from the [(99m)Tc(V)O](3+) core to the discovery of superior tracers based on the fac-[(99m)Tc(I)(CO)3](+) core. Compared to (99m)Tc-MAG3, fac-[(99m)Tc(I)(CO)3(NTA)](2-) (NTA(3-) = trianion of nitrilotriacetic acid) holds great promise by virtue of its efficient renal clearance via tubular secretion and the absence of hepatobiliary elimination, even in patients with severely reduced renal function. We report here NMR, molecular (X-ray) structure, and solution data on fac-[Re(I)(CO)3(NTA)](2-) with a -CH2CO2(-) dangling monoanionic chain and on two fac-[Re(I)(CO)3(L)](-) analogues with either a -CH2CONH2 or a -CH2CH2OH dangling neutral chain. In these three fac-[Re(I)(CO)3(L)](n-) complexes, the fac-[Re(I)(CO)3(N(CH2CO2)2)](-) moiety is structurally similar and has similar electronic properties (as assessed by NMR data). In reported and ongoing studies, the two fac-[(99m)Tc(I)(CO)3(L)](-) analogues with these neutral dangling chains were found to have pharmacokinetic properties very similar to those of fac-[(99m)Tc(I)(CO)3(NTA)](2-). Therefore, we reach the unexpected conclusion that in fac-[(99m)Tc(I)(CO)3(L)](n-) agents, renal clearance is affected much more than anticipated by features of the core plus the chelate rings (the [(99m)Tc(I)(CO)3(N(CH2CO2)2)](-) moiety) than by the presence of a negatively charged dangling carboxylate chain.

Enhanced oral bioavailability of EGCG using pH-sensitive polymeric nanoparticles: characterization and in vivo investigation on nephrotic syndrome rats.

OBJECTIVE: Chronic kidney disease (CKD) is characterized by progressive loss of renal functions. At present, there are only limited therapeutic strategies to slow down the progress of CKD and there is an urgent need to develop new therapeutic strategies to treat CKD patients. Numerous research evidence supports the potential role of EGCG in the renal protection of CKD. However, the clinical use is still limited due to the poor oral bioavailability. The aim of this study was to develop pH-sensitive polymeric nanoparticles of EGCG to improve this deficiency. MATERIALS AND METHODS: EGCG-loaded nanoparticles (EGCG NPs) were prepared by an improved emulsion evaporation method. The formulation prepared was in spherical with uniform sizes, high encapsulation efficiencies and drug loading. The therapeutic efficacy of EGCG NPs on chronic kidney disease was investigated on model of rat Nephrotic syndrome by measuring urinary protein excretion and kidney pathology score. RESULTS: The mean particle size was found to be 91.3±0.8 nm and the encapsulation efficiency% and drug loading% of the formulation were 80.8%±1.6% and 6.3%±1.4%, respectively. The powder X-ray diffraction and differential scanning calorimetry of EGCG NPs showed that EGCG existed in amorphous form in NPs. The release of EGCG from NPs exhibited the lower burst release at pH 1.2 (<10%) and with the increase of pH value, the release of EGCG also gradually increased. During the observation period (24 hours), the total release amount was almost 68%. EGCG NPs could significantly modify the pharmacokinetic profile and increase the bioavailability of EGCG by more than 2.4-fold in comparison with the EGCG powder group. At the end of the fourth and sixth week, proteinuria excretion of nephrotic syndrome rats treated with EGCG NPs was significantly lower than those treated with EGCG powder, and kidney pathology scores in EGCG NPs treated rats were also significantly lower than EGCG powder treated rats. CONCLUSION: The results of pharmacodynamics showed that compared with EGCG powder treatment group, EGCG NPs treatment group had better efficacy and reduce kidney damage.

Conformations and receptor activity of desmopressin analogues, which contain gamma-turn mimetics or a psi[CH(2)O] isostere.

Three analogues of the antidiuretic drug desmopressin ([1-desamino,8-D-arginine]vasopressin) have been prepared. In two of these, gamma-turn mimetics based on a morpholin-3-one framework have been inserted instead of residues Phe3-Asn5, whereas the third analogue has a methylene ether isostere in place of the amide bond between residues 3 and 4. The three analogues were used to probe if the structure determined for desmopressin in aqueous solution, which contains an inverse gamma-turn centered around Gln4, is important in interactions with the vasopressin V(2) receptor. Conformational studies revealed that the analogues that contain either an inverse gamma-turn mimetic or a methylene ether isostere mimicked the conformation of desmopressin fairly well and very well, respectively. Despite this, the analogues displayed only very low agonistic activities at the vasopressin V(2) receptor. Consequently, an inverse gamma-turn involving residues Phe3-Asn5 does not appear to be important when desmopressin is bound to the V(2) receptor. In addition, it was concluded that the amide bond between Phe3 and Gln4 in desmopressin is crucial for interactions with the antidiuretic V(2) receptor.

[Vasopressin: cellular and molecular aspects of its antidiuretic effect]. / Vazopressin: kletochnye i molekuliarnye aspekty antidiureticheskogo deistviia.

The paper reviews current data on molecular mechanisms of action of the neuropituitary hormone vasopressin (VP) on the aqueous epithelial permeability of the amphibian renal tubules and urinary bladder. It considers the structure and function of VP receptors, cAMP-dependent cellular events induced by VP, the action of different modulators on the effects of VP, the structure and localization of proteins that water-forming channels within the cellular membranes along the renal tubules. The development of VP sensitivity in ontogenesis is shown to be associated with age-related changes in the membrane receptor complex and with the higher activity of the adenylate cyclase mechanism.

Safe and efficient transdermal delivery of desmopressin acetate by iontophoresis in rats.

Iontophoretic delivery of desmopressin acetate (DDAVP) was assessed for delivery efficiency and drug stability, both in vitro and in vivo. The effect of current intensity and duration of current application on the decomposition of DDAVP was investigated in vitro. It was shown that when a current of 0.1 mA was applied for 5 min, the decomposition of DDAVP was negligible. In vivo experiments under the same conditions showed that the antidiuretic response to DDAVP persisted for about 6 h. Furthermore, when this iontophoresis was repeated 3 times at intervals of 4 h, the antidiuretic response persisted for about 11 h. These results suggest that repeated short-term iontophoresis is a safe and effective technique for transdermal delivery of DDAVP.

Influence of 1-aminocyclohexane-1-carboxylic acid in position 2 or 3 of AVP and its analogues on their pharmacological properties.

In this study we describe the synthesis and some pharmacological properties of seven new analogues of arginine vasopressin (AVP) substituted in position 2 or 3 with 1-aminocyclohexane-1-carboxylic acid (Acc). All peptides were tested for the pressor, antidiuretic and uterotonic in vitro activities. The Acc3 modifications of AVP, dAVP, [d-Arg8]VP and [Cpa1]AVP have been found to be deleterious for interaction with all three neurohypophyseal hormone receptors, as judged from the several orders of magnitude decreased biological activities, whereas Acc2 substitution selectively altered the interaction with the receptors. Two of the new analogues, [Acc2]AVP and [Acc2, d-Arg8]AVP, are potent antidiuretic agonists. [Acc2]AVP exhibits moderate pressor agonistic activity and weak antiuterotonic properties. [Acc2, d-Arg8]AVP has been found to be a weak antagonist in the pressor and uterotonic tests. Another analogue - [Cpa1, Acc3]AVP - turned out to be a highly selective V2 agonist. This is an unexpected effect, as its parent peptide, [Cpa1]AVP is a very potent V1a receptor antagonist. This is the first Cpa1 modification to have resulted in V2 agonism enhancement. Besides providing useful information about structure-activity relationships, our results could open up new possibilities in the design of highly potent and selective V2 agonists.

[Development of formulations of desmopressin intranasal drops]. / Dezmopresino intranazaliniu lasu technologijos sukurimas.

In recent years synthetic vasopressin analogues (particularly desmopressin) emerged as safe and effective representatives of this class of drugs for same clinical indications as natural hormone. It was imperative to create intranasal drug form using synthetic desmopressin compound. The purpose of this work was to develop formulations of intranasal desmopressin drug using synthetic active compound with optimal composition. Aquatic desmopressin intranasal solution was prepared in 0.05 mg/ml concentration using phosphate buffer (pH 4.5-5.5) and following preservatives: nipagin-nipazol 7:3--0.1% or benzalkonium chloride 0.01%. Sterility is the main condition for intranasal drops and hormones as a raw material are thermolabile so it is not possible to apply a thermic sterilisation. Polymeric membrane filters of 0.22 micron pore size were employed as sterilizing filters. In order to control the quality, to determine the stability of desmopressin intranasal drops at long-lasting storage (24 months) and to evaluate the influence of the technological factors we have developed the analytical methods of quality control. According to our quality control data, desmopressin intranasal drops are stable for two years and remain sterile during storage and administration of the drug.