Radioiodinated p-phenylene bridged fatty acids as new myocardial imaging agents: syntheses and biodistribution in rats

Tracer kinetic modeling in nuclear cardiology

The introduction of tracer kinetic modeling techniques in conjunction with nuclear imaging has allowed the assessment of physiologic processes in the myocardium in a noninvasive and quantitative manner. Alongside the development of novel radiopharmaceuticals for both positron emission tomography and single photon emission computed tomography is the clarification of their pharmacology, pharmacokinetics, and modeling strategies for assessment of physiologic rates from imaging data. Image analysis and tracer kinetic modeling techniques used in nuclear cardiology must address unique considerations related to the heart. The most commonly used tracers and modeling techniques are presently discussed, with particular attention given to methods that allow absolute quantitation of physiologic processes. The applications of these techniques are obvious in research protocols and may find more use in future clinical studies.

In vitro antiviral activities of myristic acid analogs against human immunodeficiency and hepatitis B viruses

A group of myristic acid analogs, designed as alternative substrates for N-myristoyltransferase (NMT), were evaluated against human immunodeficiency virus (HIV), hepatitis B virus (HBV) and duck hepatitis B virus (DHBV) in vitro. Antiviral potency was increased when S or O was substituted for -CH2- in myristic acid and selectivity was affected by the presence and position of the heteroatoms and phenyl groups. A correlation was established among anti-HIV activity, Log P and Log D7.4 and between anti-HIV activity and carbonyl-heteroatom interatomic distances in the myristoyl analogs. 12-Thioethyldodecanoic acid 6 was moderately active (EC50 = 9.37 microM) against HIV-infected T4-lymphocytes (CEM-SS cell line), and it exhibited in vitro activity (EC50 = 17.8 microM) against HBV-producing 2.2.15 cell cultures derived from a human hepatoblastoma cell line (Hep G2). 12-Methoxydodecanoic acid 1 exhibited in vitro activity (EC50 = 20-30 microM) against hepatitis B in the HBV DNA-transfected 2.2.15 cell line. At a concentration of 10 microg/ml, none of the fatty acids significantly inhibited the replication of DHBV in infected hepatocytes.

Synthesis and antifungal activities of myristic acid analogs

Myristic acid analogs that are putative inhibitors of N-myristoyl-transferase were tested in vitro for activity against yeasts (Saccharomyces cerevisiae, Candida albicans, Cryptococcus neoformans) and filamentous fungi (Aspergillus niger). Several (+/-)-2-halotetradecanoic acids including (+/-)-2-bromotetradecanoic acid (14c) exhibited potent activity against C. albicans (MIC = 39 microM), C. neoformans (MIC = 20 microM), S. cerevisiae (MIC = 10 microM), and A. niger (MIC < 42 microM) in RPMI 1640 media. Improved synthetic methods have been developed for the synthesis of 12-fluorododecanoic acid (12a) and 12-chlorododecanoic acid (12c). Three novel fatty acids, 12-chloro-4-oxadodecanoic acid (8a), 12-phenoxydodecanoic acid (12i), and 11-(4-iodophenoxy)-undecanoic acid (13d) were also synthesized and tested.

Iodine-123-labelled fatty acids for myocardial single-photon emission tomography: current status and future perspectives

Renewed interest in the clinical use of iodine-123-labelled fatty acids is currently primarily focused on the use of iodine-123-labelled 15-(p-iodophenyl)pentadecanoic acid (IPPA) and "modified" fatty acid analogues such as 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) which show delayed myocardial clearance, thus permitting single-photon emission tomographic imaging. Interest in the use of BMIPP and similar agents results from the differences which have often been observed in various types of heart disease between regional myocardial uptake patterns of [123I]BMIPP and flow tracer distribution. Although the physiological basis is not completely understood, differences between regional fatty acid and flow tracer distribution may reflect alterations in important parameters of metabolism which can be useful for patient management or therapy planning. These tracers may also represent unique metabolic probes for correlation of energy substrate metabolism with regional myocardial viability. The two agents currently most widely used clinically are 123I-labelled IPPA and BMIPP. While [123I]IPPA is commercially available as a radiopharmaceutical in Europe (Cygne) and Canada (Nordion), multicenter trials are in progress in the United States as a prelude to approval for broad use. [123I]BMIPP was recently introduced as Cardiodine for commercial distribution in Japan (Nihon Medi-Physics, Inc.). [123I]BMIPP is also being used in clinical studies on an institutional approval basis at several institutions in Europe and the United States. In this review, the development of a variety of radioiodinated fatty acids is discussed. The results of clinical trials with [123I]IPPA and [123I]BMIPP are discussed in detail, as are the future prospects for fatty acid imaging.

Metabolism of 15-(4'-[123I]iodophenyl)pentadecanoic acid ([123I]IPPA) in the rat heart; identification of new metabolites by high pressure liquid chromatography and fast atom bombardment-mass spectrometry

The metabolism of 15-(4'-iodophenyl)pentadecanoic acid (IPPA) in the heart muscle is commonly believed to end at 4-iodobenzoic acid as the main and final product of beta-oxidation. However, investigation of the metabolic fate of IPPA in Langendorff rat hearts using high pressure liquid chromatography (HPLC) and negative fast atom bombardment mass spectrometry (FAB-MS) revealed new results. After perfusing isolated rat hearts with [123I]IPPA, metabolites were monitored by HPLC using simultaneous detection of gamma-radioactivity and u.v. absorbance. The identification of HPLC separated metabolites was based on their nominal molecular weights as determined by negative FAB-MS. According to these measurements five catabolites were identified with decreasing concentration: 3-(4'-iodophenyl)propanoic acid >> 3-(4'-iodophenyl)propanoic acid = 5-(4'-iodophenyl)-3-hydroxypentanoic acid >> 4-iodobenzoic acid. Additionally, an anabolic metabolite was found exclusively in the lipid ester fraction. From the hydrolysed heart lipids this compound was identified as 11-(4'-iodophenyl)undecanoic acid. Its formation is explained by the action of cytosolic fatty acid synthetase on IPPA catabolites. This metabolic behaviour may be of importance for the interpretation of sequential heart scintigraphy performed with [123I]IPPA.