Fast and cost-effective cyclotron production of 61Cu using a natZn liquid target: an opportunity for radiopharmaceutical production and R&D.

Following our previous work on the production of radiometals, such as 64Cu and 68Ga, through the irradiation of liquid targets using a medical cyclotron, we describe in this paper a technique to produce 61Cu through the irradiation of natural zinc using a liquid target. The proposed method is very cost-effective, as it avoids the use of expensive enriched material, and is fast, as a purified solution of 61CuCl2 is obtained in less than 30 min after the end of beam. Considering its moderate half-life of 3.33 h and favourable decay properties as a positron emitter, 61Cu is a very attractive nuclide for the labelling of PET tracers for pre-clinical and clinical use with PET as well as to support the intense R&D programmes being carried out worldwide by taking advantage of the rich and versatile chemistry of copper.

Positron emitting tracers in pre-clinical drug development.

Molecular imaging tools such as Positron Emission Tomography (PET) are increasingly being used in the drug development process. The unrivaled sensitivity of PET coupled with a solid experience in developing highly targeted molecular probes makes this technique a very valuable tool at all stages from pre-clinical development to the clinical phases. Positron emitting tracers allow us to measure, quantitatively, molecular processes and interactions between a candidate drug and its molecular targets. This information can save time and money by directing development towards the most promising compounds and excluding molecules with unfavorable properties that would otherwise only be recognized as failures in latter stages of the process. In this paper we review the application of positron emitting tracers in the pre-clinical stages of the drug development process in the areas of oncology, cardiology, neurosciences and inflammatory diseases. PET tracers provide an important support for drug development in the areas of: discovery of new drug targets, clarification of pathophysiology, identification of potential drug candidates and validation of drug effectiveness, as well as the evaluation of pharmacokinetic and pharmacodynamic parameters in vivo.

Bursting electrical activity in pancreatic beta-cells: evidence that the channel underlying the burst is sensitive to Ca2+ influx through L-type Ca2+ channels.

In glucose-stimulated pancreatic beta-cells, the membrane potential alternates between a hyperpolarized silent phase and a depolarized phase with Ca2+ action potentials. The molecular and ionic mechanisms underlying these bursts of electrical activity remain unknown. We have observed that 10.2-12.8 mM Ca2+, 1 microM Bay K 8644 and 2 mM tetraethylammonium (TEA) trigger bursts of electrical activity and oscillations of intracellular free Ca2+ concentration ([Ca2+]i) in the presence of 100 microM tolbutamide. The [Ca2+]i was monitored from single islets of Langerhans using fura-2 microfluorescence techniques. Both the high-Ca(2+)- and Bay-K-8644-evoked [Ca2+]i oscillations overshot the [Ca2+]i recorded in tolbutamide. Nifedipine (10-20 microM) caused an immediate membrane hyperpolarization, which was followed by a slow depolarization to a level close to the burst active phase potential. The latter depolarization was accompanied by suppression of spiking activity. Exposure to high Ca2+ in the presence of nifedipine caused a steady depolarization of approximately 8 mV. Ionomycin (10 microM) caused membrane hyperpolarization in the presence of 7.7 mM Ca2+, which was not abolished by nifedipine. Charybdotoxin (CTX, 40-80 nM), TEA (2 mM) and quinine (200 microM) did not suppress the high-Ca(2+)-evoked bursts. It is concluded that: (1) the channel underlying the burst is sensitive to [Ca2+]i rises mediated by Ca2+ influx through L-type Ca2+ channels, (2) both the ATP-dependent K+ channel and the CTX- and TEA-sensitive Ca(2+)-dependent K+ channel are highly unlikely to provide the pacemaker current underlying the burst.(ABSTRACT TRUNCATED AT 250 WORDS)