THE VIABILITY OF ISOLATED RABBIT NASAL-MUCOSA IN THE USSING CHAMBER, AND THE PERMEABILITY OF INSULIN ACROSS THE MEMBRANE

The viability of isolated rabbit nasal mucosa (lateral wail) and the permeability of insulin across the membrane have been tested in an Ussing chamber. The short-circuit current (I(sc)) was relatively stable between 1 and 10 h. Average I(sc) for this period was 92 +/- 13 muA/cm2. The viability of the tissue was longer than 10-12 h, where I(sc) was about 85 and 66% of I(sc,1-10), respectively During 1-10 h the average potential difference (PD) was 6.4 +/- 1.5 mV (mucosal side was negative) and the average tissue resistance (TR) was 69 +/- 8 OMEGA cm2. The appearance of insulin at the serosal side is expressed as parts per thousand of the initial insulin concentration (8 mg/ml) at the mucosal side. Mean appearance rate was 0.44 +/- 0.34 parts per thousand h-1, equivalent to an apparent penetration coefficient (P(app)) of 0.24 x 10(-6) cm/s. The same value, corrected for possible degradation and/or adsorption at the serosal side, is 0.73 +/- 0.42 parts per thousand h-1 (P(app) = 0.4 x 10(-6) cm/s). The concentration of insulin at the mucosal side between 5 and 90 min was relatively constant, the average recovery being about 85%. The method is found to be useful for physiological and toxicological studies. Whether it is useful to screen absorption enhancers for peptides remains to be confirmed.