Effects of alpha-1-acid glycoprotein administration on propranolol binding and beta blockade in rats

Effects of nicotine-specific antibodies, Nic311 and Nic-IgG, on the transfer of nicotine across the human placenta

The adverse effects of smoking during pregnancy on fetal development are, in part, due to nicotine. These effects may be due to the actions of nicotine in fetal circulation or on placental functions. In pregnant rats, vaccination with a nicotine immunogen reduces the transfer of nicotine from the maternal to fetal circulation. However, extrapolation of these results to pregnant women might not be valid due to the well-recognized differences between human and rat placentas. In the current investigation, the effects of nicotine-specific antibodies on the transfer of nicotine from the maternal to fetal circuit of the dually perfused human placental lobule were determined. Two types of nicotine-specific antibodies were investigated; nicotine-specific mouse monoclonal antibody (Nic311, K(d) for nicotine 60nM) and IgG from rabbits vaccinated with a nicotine immunogen (Nic-IgG, K(d) 1.6nM). Transfer of the antibodies from maternal to fetal circuits was negligible. Both rabbit Nic-IgG and, to a lesser extent, mouse monoclonal Nic311 significantly reduced nicotine transfer from the maternal to fetal circuit as well as the retention of the drug by placental tissue. These effects were mediated by a substantial increase in the protein binding of nicotine and a reduction in the unbound nicotine concentration. Therefore, the data cited in this report suggest that the use of nicotine-specific antibodies might reduce fetal exposure to the drug, and that antibody affinity for nicotine is a key determinant of the extent of nicotine transfer.

Monoclonal digoxin-specific antibodies induce dose- and affinity-dependent plasma digoxin redistribution in rats

The effect of three monoclonal digoxin-specific antibodies on total and free digoxin plasma disposition was studied in rats in order to determine the role of affinity constant (Ka) and dose. Thirty minutes after digoxin infusion, administration of a stoichiometrical dose of the ICIO, 6C9 and 9F5 IgG (Ka = 6 10(9), 3.1 10(8) and 2.5 10(7) M-1, respectively) resulted in a plasma digoxin increase linearly related to Ka. The mean free plasma digoxin was 0.6 +/- 0.4, 7.8 +/- 3.3 and 43 +/- 22% respectively after 1C10, 6C9, and 9F5 IgG infusion in comparison to 70 +/- 9% in the control group. When the IgG:digoxin ratio increased from 1 to 5, plasma digoxin Cmax and AUCT also increased as a function of both affinity (Ka) and dose (N), but not linearly. The product of NKa defined an immunoreactivity factor that was well fitted to the digoxin redistribution parameters (Cmax and AUCT) by a Hill equation.

Influence of albumin on isoprenaline and propranolol effects on isolated rat uterus

We investigated the effect of albumin (6%) on the (+/-)-isoprenaline-induced relaxation of strips of isolated rat uterus and its antagonism by (-)-propranolol. The mean isoprenaline EC50 in the presence of albumin was significantly less than that in the absence of albumin (geometric mean 1.94 +/- 3.33 versus 3.21 +/- 3.50 nM, respectively; n = 14; p = 0.006, paired t test). This indicates enhancement of isoprenaline activity by albumin which could not be explained by protein binding, as this would have reduced activity. Geometric mean control KB values for inhibition of isoprenaline by propranolol at 26.8 and 500 nM were 0.835 +/- 1.68 (n = 10) and 0.889 +/- 1.60 nM (n = 34), respectively. In the presence of 6% albumin, KB for propranolol was increased significantly to 13.3 +/- 1.8 nM (n = 27, p < 0.001). Calculation of KB in terms of the measured propranolol unbound concentration of 26.8 nM, after taking into account the lower isoprenaline EC50 in the presence of albumin, yielded a mean value of 0.725 +/- 1.86 nM, which was not significantly different from either control (p > 0.05). Therefore, propranolol activity was as predicted by the unbound drug concentration in contrast to isoprenaline activity. We conclude that albumin can alter in vitro drug activity by mechanisms in addition to the reduction of unbound drug concentration.