Journal of Pharmacy and Pharmacology JPP 2001, 53: 1131–1138  2001 The Authors Received September 5, 2000 Accepted April 5, 2001 ISSN 0022-3573 Transport studies of insulin across rat jejunum in the presence of chicken and duck ovomucoids Vikas Agarwal, Sami Nazzal, Indra K. Reddy and Mansoor A. Khan Abstract Our aim was to evaluate the transport of insulin across rat jejunum in the presence of ovomucoids and to assess the effect of ovomucoids on intestinal tissue by studying the permeation of a lipophilic and a hydrophilic marker. Rat jejunal segments were mounted in a side-by-side diffusion chamber filled with Krebs bicarbonate buffer, bubbled with 95 % O 2 /5% CO 2 at a fixed flow rate and maintained at 37C. The permeation of insulin, a lipophilic marker ([7- 3 H] testosterone) and a hydrophilic marker (D-[1- 14 C] mannitol) was evaluated in the presence of 0.5–1.5 μ duck ovomucoid (DkOVM) or chicken ovomucoid (CkOVM). For stability and permeation of insulin in the presence of α-chymotrypsin, an enzyme-to-inhibitor ratio of 1 : 1 and 1 : 2 was used. In the absence of α-chymotrypsin, the permeability coefficient (P app ) of insulin at pH 7.4 was 0.9220.16810 - 7 cm s - 1 , which decreased with increasing concen- trations of DkOVM or CkOVM. Conversely, the permeation of the hydrophilic and lipophilic marker increased with increasing concentrations of CkOVM and DkOVM. In stability studies, the percentage of drug remaining was found to be 2-fold higher at the 1:2 ratio than with the 1:1 ratio of enzyme to inhibitor. This was in agreement with the 2-fold increase in flux values of insulin in the presence of α-chymotrypsin and DkOVM at the 1:2 ratio of enzyme to inhibitor. The decrease in permeation of insulin in ovomucoids was unexpected. Marker transport studies indicated that ovomucoids have the potential to modulate transcellular and paracellular permeability. The flux enhancement of insulin in the presence of α-chymotrypsin and DkOVM is encouraging. The use of ovomucoids offers potential to enhance oral delivery of insulin and warrants further investigation. Introduction Enzymatic degradation and epithelial permeability of proteins across the gas- trointestinal tract are two important factors that affect their oral bioavailability. Insulin is one of the most widely studied proteins for oral delivery. It has been demonstrated that insulin can be absorbed in the gastrointestinal lumen when protected by appropriate concentrations of enzyme inhibitor (Bendayan et al 1990). Enzymatic degradation of insulin in the gastrointestinal tract is mediated by α- chymotrypsin and trypsin in the lumen (Ginsburg & Schachman 1960 ; Young & Carpenter 1961 ; Schilling & Mitra 1991) and insulin-degrading ezyme (IDE) in the gut wall (Bai & Chang 1996 ; Chang et al 1997). Consequently, inhibitors of these enzymes have the potential to enhance the oral delivery of insulin. Enzyme inhibitors have been evaluated for oral delivery by in-vitro intestinal studies, in-situ Department of Pharmaceutical Sciences, Texas Tech University HSC, School of Pharmacy, Amarillo, TX 79106, USA Vikas Agarwal, Sami Nazzal, Indra K. Reddy, Mansoor A. Khan Correspondence : Mansoor A. Khan, Department of Pharmaceutical Sciences, Texas Tech University HSC, School of Pharmacy, Amarillo, TX 79106, USA. E-mail : khanama.ttuhsc.edu Acknowledgements : We thank Dr Michael Laskowski Jr for a sample of duck ovomucoid and Dr Zahid Amjad for support and encouragement. Dean Arthur Nelson and Dr Quentin Smith are acknowledged for their support of Drug Delivery and Formulation Center in the School of Pharmacy. 1131 Downloaded from https://academic.oup.com/jpp/article/53/8/1131/6149629 by guest on 30 June 2022