ABSTRACT
Aim To investigate the effects of different species Fc receptors (FcRn) on pharmacokinetic characteristics of MIL94, a monoclonal antibody against West Nile virus developed by Academy of Military Sciences, which has a neutralizing effect on West Nile virus and whose maintenance time in vivo is closely related to its antiviral effect. Methods The pharmacokinetic characteristics of MIL94 in mice expressing FcRn of different species (wild-type mice, hFcRn mice and FcRn knockout mice) were compared-. Wild-type mice and FcRn knockout mice were injected intravenously with MIL94 respectively. HFcRn mice were randomly divided into four groups. Two groups were injected intravenously with MIL94, and the other two groups were injected intravenously with intravenous immunoglobulin (IVIG) and then intravenously with MIL94. Indirect ELISA was used to determine the MIL94 concentration in mouse serum. WinNonlin software was used to calculate the pharmacokinetic parameters. Results After intravenous injection with MIL94, the in vivo pharmacokinetics were basically linear. The distribution volume of MIL94 in animals was related to FcRn. The half-life in vivo varied greatly between different groups. Conclusions FcRn can affect the half-life of MIL94 in different species mainly via alternation of its elimination and distribution. It is expected that the half-life of FcRn in human will be longer than that in preclinical animals.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of interstitial cells of Cajal (ICC) on contraction of intestinal tract smooth muscle induced by motilin receptor agonist.</p><p><b>METHODS</b>Two kinds of smooth muscle segments were isolated from the duodenum and colon of rabbit. Both kinds of smooth muscle were divided into two groups: group a (normal ICC group of duodenum); group c (impaired ICC group of duodenum); group b (normal ICC group of colon); group d (impaired ICC group of colon), each group contained 20 segments. The impairment of ICC was induced by selectively destroying ICC in the smooth muscle via treatment with methylene blue plus light. Then the frequency and amplitude of contraction of group a and c, group b and d was compared. Then motilin receptor agonist (ABT-229) was added into the Krebs solution, the frequency and amplitude of smooth muscle contraction before and after adding ABT-229 were recorded and compared.</p><p><b>RESULTS</b>The electron microscopy demonstrated that ICC in methylene blue plus light group were destroyed; the smooth muscle cells and neuron scattered close to ICC were normal. In group a, the contraction frequency, (17.89 +/- 1.88) times/min, was significantly lower as compared with that measured after ABT-229 was added [(18.76 +/- 1.18) times/min (P > 0.05)]; the amplitude of group a was (343 +/- 28) mg, which was lower as compared with that after adding ABT-229 [(597 +/- 68) mg (P < 0.001)]; in group b, the frequency was (5.89 +/- 1.03) times/min, the amplitude was (724 +/- 85) mg, after ABT-229 was added, the construction frequency increased to (8.45 +/- 0.69) times/min (P < 0.001), and the amplitude was (897 +/- 89) mg (P < 0.05), which was not affected by pretreatment with TTX, however it could be weakened by nifedipine significantly. In group c and d, the rhythmic contraction almost disappeared: in group c the contraction frequency was (1.06 +/- 0.24) times/min, and the amplitude were (50 +/- 10) mg. In group d, the amplitude and frequency significantly decreased as compared with the normal group (P < 0.001), in group c, and d, no significant difference in amplitude and frequency was found between the values measured before and after adding ABT-229 (P > 0.05). After Ach (100 micromol/L) was added, both group c and d could generate contraction.</p><p><b>CONCLUSION</b>ICC may play an important role in the rhythmic contraction of intestinal tract. The promoting effect of motilin receptor agonist on intestinal tract may be mediated by ICC. ICC deficiency may cause functional impairment of gastrointestinal tract motivation. The medication may become ineffective when the number of ICC is reduced to a certain extent or the network of ICC is incomplete.</p>