Surfactant protein a in rabbit sinus and middle ear mucosa

In the present study, pulmonary surfactant protein A (SP-A) messenger RNA ( mRNA) and protein were characterized in adult rabbit middle ear and maxilla ry sinus. Fifteen adult rabbits were used for the study: 6 with evidence of acute middle ear infections and maxillary sinusitis, 6 with infections tha t were successfully treated with tetracycline, and 3 that were pathogen-fre e. We detected SP-A mRNA in maxillary sinus and middle ear tissues by North ern blot analysis and reverse transcriptase-polymerase chain reaction (RT-P CR). The RT-PCR also revealed the presence of SP-B and SP-C mRNA in middle ear and sinus tissues. We detected SP-A protein, of molecular weight approx imately 29 and 70 kd, in middle ear and sinus tissues by immunoblot analysi s. Unlike the SP-A protein present in the lung, the molecular weight of the SP A protein present in the middle ear and paranasal sinus was not altered by digestion with an enzyme that cleaves N-linked carbohydrates. Immunosta ining and in situ hybridization showed that SP-A protein and mRNA, respecti vely, were present in surface epithelial cells of the middle ear and in epi thelial cells of submucosal glands in sinus tissues. These data provide the first evidence of the presence of pulmonary surfactant proteins in the par anasal sinuses and confirm previous reports of SP-A in the middle ear epith elium.