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Investigating the biodistribution of cell and gene therapy products may play an important role in evaluating their safety and pharmacology. As quantitative polymerase chain reaction (qPCR) is often used for these analyses, it is essential to improve the reliability of bioanalysis performed using qPCR. In this report, the authors discuss the use of qPCR in nonclinical studies, as it can be used to detect target DNA/RNA and it is quantitative and applicable for long-term analysis. The authors also discuss points to consider during bioanalysis using qPCR and present appropriate validation items and their criteria. The authors anticipate the discussion provided herein to contribute to the development of validation and sample analysis for pharmaceuticals analyzed using qPCR.

We analyzed electropharmacological characteristics of microminipigs under halothane-anesthesia using anti-influenza virus drug oseltamivir, which has been known to possess multi-channel blocking properties, including Na+, Ca2+ and K+ channels (n = 4). Oseltamivir in doses of 0.3, 3 and 30 mg/kg was intravenously infused over 10 min with an interval of 20 min, which provided peak plasma concentrations 1.4, 7.4 and 125.5 µg/mL, respectively. The low dose did not alter any of the cardiovascular variables. The middle dose decreased the heart rate at 30 min after the start of the infusion. The high dose transiently returned the heart rate toward the baseline for 10-15 min, but decreased it for 20-60 min; decreased the mean blood pressure for 5-60 min; prolonged the PR interval for 10-60 min, and the QRS width for 10-20 min; but shortened the QT interval for 10-30 min, and the QTc for 5-60 min. Thus, oseltamivir can suppress the sinus automaticity, and atrioventricular nodal and intraventricular conduction; and decrease the mean blood pressure, extents of which were greater in microminipigs than in beagle dogs in our previous observation in spite of similar plasma concentrations, reflecting higher sensitivity of microminipigs for Na+ and Ca2+ channel inhibition than that of beagle dogs. In contrast to beagle dogs, oseltamivir shortened the repolarization period in microminipigs, indicating that oseltamivir can more potently inhibit the inward currents than the outward ones in the hearts of microminipigs. This information may help improve utilizatione of microminipigs as a laboratory animal.

Fluvoxamine is a selective serotonin-reuptake inhibitor, of which IC50 values for serotonin- and noradrenaline-uptake process were reported to be 3.8 and 620 nmol/L, respectively, also known to directly inhibit cardiac Na+, Ca2+, and K+ channels. We characterized microminipig as a laboratory animal by analyzing fluvoxamine-induced cardiovascular and dermatological responses under halothane anesthesia. Fluvoxamine maleate was infused in doses of 0.1, 1, and 10 mg/kg over 10 min with a pause of 20 min (n = 4). The peak plasma concentrations were 35, 320, and 1906 ng/mL, of which free plasma concentrations were estimated as 20, 187, and 1108 nmol/L, respectively. The low and middle doses did not alter any cardiovascular variable. The high dose increased heart rate and mean blood pressure, prolonged QRS width, but shortened QT interval, whereas no significant change was detected in PR interval or QTcF. Moreover, it induced systemic erythema on the skin. Pretreatment of H1/5-HT2A antagonist cyproheptadine hydrochloride sesquihydrate in a dose of 0.3 mg/kg significantly attenuated the fluvoxamine-induced pressor response; but tended to further enhance sinus automaticity, atrioventricular nodal conduction; and ventricular repolarization in addition to intraventricular conduction delay; whereas it markedly suppressed onset of systemic erythema (n = 4). In microminipigs, cardiovascular adverse effects of the high dose may be manifested as a sum of its inhibitory action on the cardiac ionic channels and its stimulatory effects on serotonergic and adrenergic systems, whereas dermatologic reaction can be induced primarily through H1/5-HT2A receptor-dependent mechanism. Thus, microminipigs may be used for analyzing such multifarious adverse events of clinical serotonergic pharmacotherapy.

Although azithromycin can suppress cardiac INa, IKr, IKs, ICa,L and IK1, its onset mechanisms for cardiovascular death have not been fully investigated. We examined electropharmacological effects of azithromycin in intravenous doses of 0.3, 3 and 30 mg/kg using microminipigs under the halothane anesthesia (n = 4), which provided plasma concentrations of 3.1, 11.2 and 120.4 μg/mL, respectively. The low dose did not alter any of the cardiohemodynamic or electrocardiographic variables. The middle dose significantly shortened QT interval for 10–20 min and QTc for 10–30 min. The high dose significantly decreased mean blood pressure for 5–60 min, prolonged QRS width at 20 min, but shortened QT interval for 15–20 min and QTc for 15–30 min (n = 3). Cardiohemodynamic collapse occurred in 1 animal after the start of the high dose infusion, which might be associated with the cardiovascular death in patients with vasomotor dysfunction. Prolongation of QRS width indicates that azithromycin may suppress ventricular INa in vivo, which may unmask latent type of Brugada electrocardiographic genotype. Meanwhile, abbreviation of the QTc might cause potentially lethal, short QT-related, cardiac arrhythmia syndrome. These findings with microminipigs suggest the possible entry point for analyzing the mechanisms of cardiovascular death clinically seen with this antibiotic. Keywords: Azithromycin, Microminipigs, Short QT syndrome, Brugada syndrome, Hypotension

Using isolated scales and split-fin preparations of the tilapia Oreochromis niloticus, the effects of a pair of prolactins of the tilapia Oreochromis mossambicus (tPRL177 and tPRL188) and of ovine prolactin (oPRL) on chromatophores were studied in vitro. These peptides caused melanosome aggregation and dispersion of xanthosomes, especially in the split preparations. Their relative effectiveness was as follows: tPRL177 > oPRL > tPRL188. Moreover, tPRL177 at 100 nM induced a high level of pigment dispersion in cultured xanthophores and erythrophores, but tPRL188 at the same concentration did not have this effect. We also examined the responses of chromatophores to oPRL in primary cell culture and found that xanthophores and erythrophores respond to the peptide by pigment dispersion in a dose-dependent manner, whereas cultured melanophores showed little aggregation of pigment. In denervated melanophores in the split-fin preparations, tPRL177 failed to induce aggregation of pigment. From these results, it was concluded that prolactin affects brightly pigmented cells of the tilapia directly, but affects melanophores indirectly. Norepinephrine which might leak from varicosities of chromatic nerve fibers by virtue of the action of prolactin molecules may be responsible for melanosome aggregation.