Received: 18 April 2016
Revised: 30 June 2016
Accepted: 26 July 2016
DOI 10.1002/jlcr.3435
RESEARCH ARTICLE
Radioiodination and biological evaluation of candesartan as a tracer for cardiovascular disorder detection M.H. Sanad* | Kh.M. Sallam | F.A. Marzook | S.M. Abd‐Elhaliem Labeled Compounds Department, Radioisotopes Production and Radioactive Sources Division, Hot Laboratories Center, Atomic Energy Authority, P.O. Box 13759, Cairo, Egypt Correspondence M.H. Sanad, Labeled Compounds Department, Radioisotopes Production and Radioactive Sources Division, Hot Laboratories Center, Atomic Energy Authority, P.O. Box 13759, Cairo, Egypt. Email:
[email protected]
The goal of the study aims to evaluate newly radioiodinated candesartan (CAN) as a potential cardiovascular tracer. CAN was labeled using 125I with chloramine‐T (Ch‐T) and N‐bromosuccinimide (NBS) with full characterization of cold Iodo‐ candesartan. Factors such as pH, reaction temperature, reaction time, substrate, and oxidizing agent amounts were studied to optimize the radioiodination of CAN. The optimum radiochemical yield of 125I‐CAN was 98%. The labeled compound was separated and purified using high‐pressure liquid chromatography. The biological distribution indicates the suitability of 125I‐CAN as a novel tracer to detect cardiovascular disorders. KE YWO RD S
biological distribution, candesartan, cardiovascular, radioiodination
1 | IN T RO D U C T IO N Candesartan (CAN) is an angiotensin II receptor blocker (ARB). ARBs are widely used in treating diseases such as hypertension, heart failure, myocardial infarction, and diabetic nephropathy. CAN is a tetrazole derivative (5‐membered heterocyclic ring with 4 nitrogen atoms). Clinically, it is used in the form of an ester prodrug— candesartan cilexetil. Candesartan cilexetil is chemically expressed as 2‐ethoxy‐3‐[21‐(1H‐tetrazol‐5‐yl) biphenyl‐ 4‐ylmethyl]‐3H‐benzoimiadazole‐4‐carboxylic acid 1‐ cyclohexyloxycarbonyloxy ethyl ester. CAN is an orally active non‐peptide tetrazole derivative. It finds its most significant clinical use in the treatment of hypertension of all grades. CAN is a potent, highly selective ARB that is devoid of agonist activity.1–4 It is also used in the treatment of congestive heart failure.5 Hypertension is one of the most prevalent cardiovascular diseases in the world, affecting a large proportion of the adult population. The ARBs represent a newer class of antihypertensive agents that help relax your blood vessels, which lower the blood pressure.6 That makes it easier for your heart to pump blood, which considers a natural substance in the body. Cardiovascular system can be affected in many ways, such as by narrowing blood vessels. Angiotensin II also starts the release of a hormone that increases the amount of sodium and water in body, which 484
Copyright © 2016 John Wiley & Sons, Ltd.
can lead to increased blood pressure and can also thicken and stiffen the walls of blood vessels and heart. ARBs block the action of angiotensin II that allows blood vessels to widen (dilate).7 The reduced pressure within the blood vessels also means that the heart does not have to work as hard to pump the blood around the body.8 The choice of the labeling site is determined by biological, chemical, and structural considerations while particular attention must be paid to the stability of the carbon‐iodine bond. The electrophilic substitution mechanism is used in case of radiolabeling of CAN, which contains an activated benzene ring. Different oxidizing agents may be used but Ch‐T is highly powerful oxidant and takes a short time to react. In the case of Ch‐T, it must be in a highly purified form to help prevent the formation of side products.9–12 The aim of this study is to investigate all factors that affect the labeling process and to optimize the conditions required to get a labeled compound with the highest radiochemical yield and purity. To that end, the biodistribution and the efficiency of labeled CAN in heart and blood vessels will be experimentally evaluated in healthy animals. In this study, 125I was used in the labeling process because of its availability, suitable energy, and half‐life for research purposes. The radioiodination of CAN 125I‐CAN (Figure 1) was developed via an electrophilic substitution reaction in the presence of Ch‐T, as the oxidizing agent.
wileyonlinelibrary.com/journal/jlcr
J Label Compd Radiopharm 2016; 59: 484–491
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2.2 | Materials and methods Candesartan was given to us by Pharaonia Company for Pharmaceutics. All other chemicals were purchased from Merck; they were reagent grade. Absolute ethanol was used as a solvent. Double‐distilled water was used for all procedures. Chloramine‐T (Ch‐T) (n‐chloro‐p‐toluene sulfonamide salt) was obtained from Sigma‐Aldrich. TLC aluminum sheets (20 × 25 cm) SG‐60F254 were supplied by Merck. Na125I (185 MBq/50 μL) diluted in 0.04 M NaOH, pH 9 to 11, was purchased from the institute of isotopes, Budapest, Hungary. 2.2.1 | Apparatus
FIGURE 1
Radioiodination of candesartan
2 | E XP E R IM E NTA L 2.1 | Experimental for synthesis of nonradioactive iodinated candesartan Candesartan (3 mmol) was dissolved in the minimum amount of THF and added to a mixture of 0.5 g silica gel, 0.1 g sulfuric acid (1 mmol), 0.35 g NaCl (6 mmol), and HIO4 or NaIO4 (3 mmol) that dissolved in 5 mL water, with stirring over 10 minutes. The reaction was monitored by thin‐layer chromatography (TLC) for 50‐minute reaction time at ambient temperature. Then the reaction mixture was treated with aqueous sodium thiosulfate, extracted with CH2C12, washed with water, and dried over anhydrous Na2SO4. Solvent was removed at reduced pressure. The solid formed was collected, washed several times with diethyl ether, and recrystallized from tetrahydrofuran yellow fine crystals, with a yield of 35%. The product (Iodo‐candesartan) was characterized by (proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR), infrared (IR) spectra, elemental analysis, and mass spectra).13,14
A well‐type NaI scintillation γ‐Counter model Scalar Ratemeter SR7 (Nuclear Enterprises Ltd., USA) was used for radioactive measurement; pH meter: model 601 A digital ion analyzer (Orion Research, USA); ionization chamber: model CRC‐15R (Capintec, USA); precision electronic balance: model HA 120 (MAD Company Ltd., Japan); stirring hot plate: model 210 T Thermix (Fisher, USA); and electrophoresis apparatus: E.C. Corporation (Albany, OR, USA). The IR spectra were recorded in potassium bromide discs on a Shimadzu FT IR 8101 PC IR spectrophotometer. The 1 H NMR spectra were recorded on a Varian Mercury VXR‐ 500 MHz spectrometer and the chemical shifts were measured as δ (ppm) downfield from tetramethylsilane (TMS) as an internal standard. 1H NMR (500 MHz) and 13 C NMR (125 MHz) were run in dimethylsulphoxide (DMSO‐d6). Mass spectra were recorded on a Shimadzu GCMS‐QP1000 EX mass spectrometer at 70 eV. All reactions were followed by TLC (Silica gel, Aluminum Sheets 60 GF254, Merck) and were detected with a 254 NM ultraviolet (UV) lamp. 2.2.2 | Radiolabeling of candesartan
In an eppendorf tube, different amounts of CAN dissolved in ethanol (1 mg:1 mL), (50‐400 μg) were added. Then, freshly prepared Ch‐T dissolved in ethanol (25‐200 μg) was added followed by the addition of 100 μL different pH buffer solutions (2‐10), followed by 10.0 μL of Na125I (0.5 mCi,
FIGURE 2
Electrophoresis of 125I‐candesartan at optimum conditions
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FIGURE 3
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High‐pressure liquid chromatography radiochromatogram of 125I‐candesartan at optimum conditions. UV, ultraviolet; CAN, candesartan
18.5 MBq). A drop of saturated sodium metabisulfite solution 150 μg of (30 mg/mL) dissolved in ethanol was added to give a total volume of reaction 750 to 850 μL. The reaction mixture was vortexed and left at ambient temperature at different time intervals 5 to 60 minutes. Then, the radiochemical yield was determined using TLC and paper electrophoresis. The mixture was completely purified using high‐pressure liquid chromatography (HPLC) column using a Shimadzu model detector SpD‐6A, the column (RP‐C18–250 mm × 4.6 mm, 5 μm, LiChrosorb) model that consists of pumps LC‐9A, Rheodyne injector, and UV spectrophotometer detector at 272 nm wavelength, eluting with (methanol, acetonitrile and 0.1% ortho‐phosphoric acid) in a ratio of 35:50:15 [v/ v/v]) as a mobile phase with a 1.0 mL/minute flow rate.15
to 3 hours. Developed strips were dried and cut into 1‐cm segments and counted by a well‐type NaI scintillation counter. The radiochemical yield was calculated as follows: ratio of the radioactivity of the labeled product to the total radioactivity ×100.
2.3 | Radiochemical analysis
2.3.4 | Factors affecting the yield percentage of 125I‐CAN
2.3.1 | Thin‐layer chromatography
The following factors were studied to obtain the optimum conditions of radiolabeling of CAN: reaction time, reaction
125
The radiochemical yield of I‐CAN was determined using aluminum‐backed silica gel 60F254.16 A volume of 5 μL reaction mixture was placed on the start line, then chromatographed using methylene chloride: ethyl acetate (2:1 v/v) as a developing system. The strips were removed, dried and cut into 1‐cm segments, and assayed for radioactivity using SR.7 gamma counter.
2.3.3 | HPLC analysis
HPLC analysis of CAN solution was done by injection of 10 μL from the reaction mixture into the column and UV spectrophotometer detector at 272‐nm wavelength. The column was eluted with a mobile phase mentioned before with a 1.0 mL/minute flow rate. Fractions of 15 mL were collected separately using a fraction collector of up to 15 mL and counted in a well‐type‐γ‐scintillation counter.
2.3.2 | Electrophoresis conditions
Electrophoresis was done with EC‐3000 p‐series programmable (E.C. Apparatus Corporation) power and chamber supply units using cellulose acetate strips. The strips were moistened with 0.05 M phosphate buffer pH 7.2 ± 0.2 and then were introduced into the chamber. Samples of 5 μL were applied at a distance of 10 cm from the cathode. The radioactivity values were evaluated at the applied voltage (300 V), and the standing time was 1.5
The effect of different oxidizing agents on the radiochemical yield reaction conditions: 10 μL (~3.7 MBq) Na125I, 75 μg of candesartan, (x μg) of Ch‐T, (y μg) of N‐bromosuccinamide, at pH 8; the reaction mixtures were kept at room temperature for 15 minutes FIGURE 4
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Variation of the radiochemical yield of radioiodinated candesartan as a function of pH; reaction conditions: 10 μL (~3.7 MBq) Na 125I, 75 μg of candesartan 50 μg of Ch‐T, at different pH; the reaction mixtures were kept at room temperature for 15 minutes FIGURE 5
temperature, pH value, and amount of both substrate and oxidizing agents. 2.3.5 | Effects of oxidizing agents and pH
The effect of different oxidizing agents and their amounts on the labeling yield were studied under reaction conditions: 10 μL (~3.7 MBq) Na125I, 75 μg of CAN (0.05 MBq/μg), (x μg) or Ch‐T or (y μg) of N‐bromosuccinimide at pH 8.0 as const. factor. The reaction mixtures were kept at room temperature for 15 minutes. Variation of the labeling yield of radioiodinated CAN as a function of pH was studied too. Reaction conditions were tested at different pH values. The reaction mixtures were kept at room temperature for 15 minutes and maximum radiochemical yield was given at pH 8.0 (optimum value) Figures 4 and 5.16 2.3.6 | Effect of candesartan concentration
Different amounts of CAN, ranging from 25 to 400 μg/mL (or) 25 to 400 μL/mL (1 mg:1 mL ethanol), were tested. Variation of the radiochemical yield of radioiodinated CAN
Variation of the radiochemical yield of radioiodinated candesartan as a function of different candesartan amounts; reaction conditions: 10 μL (~3.7 MBq) Na 125I, (x μg) candesartan, 50 μg of Ch‐T, at pH 8; the reaction mixtures were kept at room temperature for 15 minutes
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FIGURE 7 Variation of the radiochemical yield of radioiodinated candesartan as a function of reaction time; reaction conditions: 10 μL (~3.7 MBq) Na125I, 75 μg of candesartan, 50 μg of Ch‐T, at pH 8, the reaction mixtures were kept at room temperature for different intervals of time
as a function of different CAN amounts was drawn in Figure 6. Reaction conditions were as follows: 10 μL (~3.7 MBq) Na125I, (x μg) CAN, 50 μg (or) 50 μL of Ch‐T (1 mg:1 mL ethanol), at pH 8.0. The reaction mixtures were kept at room temperature for 15 minutes.16 2.3.7 | Effect of reaction time
The reaction time is one of the most important factors that affect the radiolabeling process. Therefore, different reaction times ranging from 5 minutes to 1.0 hour were examined and the results were drawn in Figure 7. Reaction conditions were as follows: 10 μL (~3.7 MBq) Na125I, 75 μg of CAN, 50 μg of Ch‐T, at pH 8. The reaction mixtures were kept at room temperature for varying intervals of time.16 2.3.8 | In vitro stability of radioiodinated candesartan
In vitro stability of radioiodinated CAN was studied over a 48‐hour period at optimum conditions (75 μg of CAN, 50 μg of Ch‐T, at pH 8, and 10 μL of Na125I) to determine the suitable time for injection to avoid the formation of the undesired radioactive products, which might be accumulated in nontarget organs. The results showed that the radioiodinated CAN was stable up to 48 hours as shown in Figure 8.16
FIGURE 6
FIGURE 8
In vitro stability of radioiodinated candesartan
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2.4 | Animal studies The experimental animals, Swiss Albino mice (25‐30 gm), were intravenously injected with 200 μL (3.5 MBq) of 125 I‐CAN adjusted to physiological pH via the tail vein and kept alive in metabolic cages for varying intervals of time under normal conditions. For quantitative determination of organ distribution, 5 mice were used for each experiment and the mice were sacrificed at different times post‐injection. Samples of fresh blood, bone, and muscle were collected in pre‐weighed vials and counted. The different organs were removed, counted, and compared to a standard solution of the labeled CAN. The average percent values of the administrated dose per organ were calculated. Blood, bone, and muscles were assumed to be 7%, 10%, and 40%, respectively, of the total body weight.11 Corrections were made for background radiation and physical decay during the experiment. Differences in the data were evaluated with the Student t test. Results for P using the 2‐tailed test are reported and all the results are given as mean ± SEM. The level of significance was set at P < .05.
3 | R E S ULT S A N D D I S C U S S I O N 3.1 | Radiochemical yield The flow rate (Rf) for free 125I = 0.0 − 0.1 and the Rf for the labeled compound were 0.9 to 1.0. The radiochemical yield percentage was calculated as the percent ratio of activity of the labeled compound relative to the total activity on the TLC strip.12
3.2 | Characterization of the synthesized 22–Iodo‐ candesartan The chemical structure of Iodo‐candesartan (molecular formula, C24H19IN6O3; melting point 190°C‐195°C) was confirmed by the following:1H NMR (DMSO‐d6), (position[P])5: δ (ppm) 7.36, ([dd,1H,C–H aromatic], J = 7.8, 0.95 Hz), (P)6: δ 6.89 ([t,1H,C–H aromatic], J = 7.8 Hz), (P)7: δ 7.83 ([dd,1H,C–H aromatic, J = 7.8 Hz]), (P)10: δ 11 ([s,1H,COOH]), (P)11: δ 3.89 ([q,2H,CH2, J = 6.91 Hz]), (P) 12: δ 1.22 ([t,3H,CH3, J = 6.91 Hz]), (P)13: δ 3.11 ([s,2H,CH2]) (P)15 and 19: δ 7.10 ([d,2H, 2C–H aromatic, J = 8.11 Hz]), (P) 16 and 18: δ 7.15 ([d,2H,2C–H aromatic, J = 8.11 Hz]), (P) 21, 23, and 24: δ 6.8 to 7.25 (m,1H,3C–H aromatic), (P) 29: δ 15.6 (s as broad band,1H,NH aromatic). 13C NMR δ ppm (DMSO‐d6) showed peaks at (P) 2: δ 158.34, (P) 4: δ164.7, (P)5: δ 121.66, (P) 6: δ 120.9, (P) 7: δ 123.33, (P) 8: δ 119.5, (P) 9: δ 141 (P) 10: δ 169, (P) 11: δ 57, (P) 12: δ 14.7, (P) 13: δ 35.8, (P) 14: δ 138, (P) 15&19: δ 127, (P) 16 &18: δ 128.5, (P) 17: δ 138, (P) 18: δ 14.7), (P) 20: δ 138.8, (P) 21: δ 133, (P) 22: δ 91, (P) 23: δ 134, (P) 24: δ 130, (P) 25: δ 122.6, (P) 26: δ 152.8. The IR spectrum (υ,
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cm‐1) exhibited bands at 2800 to 3690 (OH of carboxylic acid moiety); 3088 (aromatic C–H); 2930 (aliphatic C–H); 1710 (the carbonyl group of carboxyl group); and 3450 (NH group of tetrazole ring). Its mass spectra showed the molecular ion peak at [M + 1]+ (at m/z 567.05). Elemental analysis calculated for C24H19N6O3I (567): 50.88% C, 3.35% H, 14.84% N found C 50.89%; H, 3.36%; N 14. 87%. It was observed that these results in agreement with Bhanu R. et al. 2011.17 3.3 | Electrophoresis results Analysis of the 125I‐candesartan reaction mixture at optimum conditions resulted in 2 peaks as shown in Figure 2. One corresponding to the free iodide that moved towards the anode at 12‐cm distance while the 125I‐CAN remained at the point of spotting, depending on its charge and ionic mobility.10 It gave a radiochemical yield equivalent to 98.0%. 3.4 | HPLC purification As shown in Figure 3, 3 peaks were obtained. The first peak was at 2.5 minutes, whereas the second peak was at 6.9 minutes and the third peak was at 7.7 minutes retention time. The first peak corresponds to free iodide, whereas the second peak corresponds to UV CAN and the third peak corresponds to 125I‐CAN as shown in Figure 3.15 The differences in the retention time between UV of CAN and 125 I‐CAN may be attributed to increasing of the hydrophobicity of labeled compound upon incorporation of iodine in aromatic rings that made this difference in retention times. 3.5 | Effect of different oxidizing agents and their amounts Two different oxidizing agents, Ch‐T and N‐bromosuccinimide (NBS), were used. The results are shown in Figure 4. The Ch‐T method gave a higher radiochemical yield percentage than that obtained from the NBS method. This concludes that Ch‐T is a more powerful oxidizing agent than NBS.18 3.6 | Effect of pH Different values of pH ranging from 1.0 to 10 were used. As shown in Figure 5, the radiochemical yield percentage increased by increasing pH value up to 8, which recorded the maximum yield percentage. The results revealed that with any increase in pH value over 8.0, a reduction in the yield percentage was observed. This finding is in agreement with many publications of Ayoub, 2008.12 3.7 | Effect of candesartan amounts As shown in Figure 6, 85 μg of CAN was sufficient to reach the highest radiochemical yield percentage 98%. There is no significant rise in radiochemical yield by adding other
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amounts of CAN (more than 85 μg) as indicated in the results that are in agreement with Sand et al., 2015.19 3.8 | Effect of reaction time As shown in Figure 7, results indicated that the yield percentage grew by increasing the reaction time by up to 15 minutes. It was concluded that 15 minutes is the optimal time needed to reach the highest radiochemical yield percentage.16 3.9 | In vitro stability In vitro stability of radiolabeled CAN tracer was studied for a 48‐hour period. The results in Figure 8 show a high stability of 125I‐CAN tracer in vitro. This stability helps in using this product for injection in vivo. 3.10 | Biodistribution study Biodistribution tracing of 125I‐CAN reflects selective targeting to tissue‐rich angiotensin receptors, as shown in
Heart/blood ratio of radioiodinated candesartan in normal male Swiss Abino mice as a function of time
FIGURE 9
TABLE 1
Table 1. 125I‐CAN was distributed rapidly in blood, heart, kidneys, and liver at 5 minutes post‐injection. After 1 hour, the 125I‐CAN uptake significantly decreased in the blood, kidneys, intestine, and liver. The heart showed high–125I‐CAN selective uptake that equal to 19.5, 17.5, and 14.8, 10.9 and 6.8% ID/g at 5, 15, 30, 60, and 120 minutes post‐injection, respectively. Tissue selective stability of 125 I‐CAN elucidated high‐receptor binding stability to angiotensin II receptor subtype II. This is also augmented by the fact that rapid heart uptake is higher than that of 125 I‐valsertan16 and 99mTc‐valsertan20 that have maximum heart uptake of (17% ± 0.9% at 1 hour) and (11 ± 0.3), respectively. At the same time, the blood ratio of 125I‐ valsertan was (11% ± 1.0% at 1 hour), so the imaging of the heart at this time is not suitable and the heart/blood ratio was 1.5 times.19 But in case of 125I‐CAN, the maximum suitable percentage was 15 ± 0.33 at 30 minutes post‐injection and the blood ratio was 3 ± 0.2, so the heart/blood ration was 5 times that more than maximum ratio of 125I‐valsertan (Figure 9); in addition, 125I‐CAN showed high–heart/lung
Heart/liver ratio of radioiodinated candesartan in normal male Swiss Abino mice as a function of time
FIGURE 10
Biodistribution of 125I‐CAN in normal mice at different times
Organs and Body Fluids
% ID/gram and Body Fluid at Different Times Post‐injection 5 min
15 min
30 min
Blood
22.5 ± 0.14
15.8 ± 0.23
3.1 ± 0.18
1.7 ± 0.001
1.0 ± 0.002
Bone
1.0 ± 0.01
0.96 ± 0.001
1.21 ± 0.003
1.1 ± 0.001
0.98 ± 0.002
Muscle
60 min
120 min
1.0 ± 0.001
1.1 ± 0.003
1.85 ± 0.004
0.9 ± 0.001
0.70 ± 0.001
Brain
0.21 ± 0.001
0.19 ± 0.002
0.23 ± 0.003
0.16 ± 0.001
0.18 ± 0.003
Lungs
1.1 ± 0.001
1.0 ± 0.002
0.90 ± 0.003
0.87 ± 0.003
0.75 ± 0.002
Heart Liver
19.5 ± 0.51
17.5 ± 0.11
14.80 ± 0.33
10.90 ± 0.44
6.80 ± 0.15
3.6 ± 0.14
6.1 ± 0.18
.4 ± 0.24
5.11 ± 0.11
1.12 ± 0.18
5.28 ± 0.16
12.9 ± 0.41
29.5 ± 0.12
20.5 ± 0.18
8.10 ± 0.13
1.1 ± 0.001
0.90 ± 0.001
1.11 ± 0.002
0.95 ± 0.003
0.70 ± 0.001
Intestine
1.90 ± 0.001
3.90 ± 0.22
8.30 ± 0.22
5.40 ± 0.01
3.90 ± 0.15
Stomach
1.0 ± 0.001
0.95 ± 0.003
0.90 ± 0.001
0.85 ± 0.001
0. 80 ± 0.002
Thyroid
0.9 ± 0.001
0.7 ± 0.002
0.8 ± 0.001
1.0 ± 0.003
1.11 ± 0.001
Kidneys Spleen
Values represent mean ± SEM, n = 5.
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ratio up to 17 times indicating that 125I‐CAN has more cardio‐ selective than other technetium cardio‐tracers; also, it has high–heart/liver ratio up to 6.1 at 2 hours (Figure 10). The high‐myocardial imaging superiority of 125I‐CAN as possible imaging agent with high‐spatial resolution,21–23 high– 125 I‐CAN uptake for angiotensin II receptor subtype II tissue‐rich such as heart tissue may give us a glimpse of as a possible medical trial using nonradioactive I‐CAN as possible potential antihypertensive agent. Being a tissue‐rich with angiotensin II receptor subtype II, the kidney showed high‐ radioactivity uptake and low clearance augmented by low‐ water solubility of 125I‐CAN, equal to 5, 13, 30, and 21 at 5, 15, 30, and 60 minutes, respectively. A similar profile between liver and intestine was observed indicating some enterohepatic circulation.24–29 Results of the radioactive uptake of both kidney and liver are compatible with data published by Sidiqui et al. who mentioned that the main elimination route of mother drug CAN is through hepatobiliary and urinary pathways.6 The thyroid uptake ranged from 0.9% to 1.11% within 2 hours, indicating that 125 I‐CAN is a free‐form radioiodide and it is stable in vivo.23 The tracer was extracted through hepatobiliary and urinary pathways. The uptake percent of 125I‐CAN is sufficient for myocardial imaging.30–33
4 | C O NC LUS I O N Candesartan can easily be labeled with radioactive iodine. 125I‐ CAN gives a high‐radiochemical yield of 98%, in the presence of 75 μg CAN and 50 μg chloramine‐T when used at room temperature within 15 minutes. Biodistribution assessments indicate that 125I‐CAN is a selective targeting agent for angiotensin II receptor subtype II rich tissues with no detectable receptor binding interference. 125I‐CAN can be easily and safely used in myocardial imaging where further clinical trials are needed for nonradioactive 125I‐CAN as a possible antihypertensive agent as a selective angiotensin II receptor subtype II antagonist. AC KNOWLEDGEMENTS
The authors wish to thank Assistant Prof. Dr. Alhussein A. Ibrahim for critical reading and helpful suggestions on the synthesized cold iodo compound by applied Org. Chem. Dept. Chemical Industries Division, National Research Center, Tahrir St., Dokki, Giza, Egypt. CONFLICT OF INTEREST
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The authors report no conflict of interest.
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How to cite this article: Sanad, M. H., Sallam, Kh. M., Marzook, F. A., and Abd‐Elhaliem, S. M. (2016), Radioiodination and biological evaluation of candesartan as a tracer for cardiovascular disorder detection. J. Label Compd. Radiopharm, doi: 10.1002/jlcr.3435
