Expression of PAM forms and activity in the olfactory epithelium. A, Northern blot analysis. Total RNA from olfactory epithelium (10 μg) was probed with cDNA against a PAM 1.3 kb fragment. Standardization was performed using S26. Scion Image Analysis yielded density ratios of PAM/S26 for E13 (0.16), postnatal day 2 (P2; 0.27), 2.5 weeks (0.34), Adult (0.41), and 14 months (0.56). Analysis was repeated three times with similar results.B, Western blot of PAM protein. Western blots were performed using 20 μg of protein extract from the olfactory epithelium (OE) of rats of the indicated ages. The blot was probed with affinity-purified antibody against Exon A. C, Left, Schematic identifying the antigen used to generate the Exon A antibody (horizontal bar), as well as full-length PAM-1 (PAM-1; 120 kDa), membrane PAL (PAL_m; 70 kDa), and soluble PHM (PHM_s ; 44–46 kDa) and PAL (PAL_s ; 50 kDa). Arrowsindicate major proteolytic cleavage sites. Right, Adult olfactory epithelium probed with the Exon A antibody (ExonA) and immunodepleted antibody (Ctrl). D, PHM enzymatic activity. Enzyme activity was calculated as picomoles of substrate produced per microgram of protein per hour. Error bars indicate SE. Four independent sets of extracts were assayed. mo, Months;wk, weeks.