Getchell T V, Su Z, Getchell M L
Department of Physiology and Biophysics, University of Kentucky College of Medicine, Lexington 40536.
Ciba Found Symp. 1993;179:27-40; discussion 40-50. doi: 10.1002/9780470514511.ch3.
Access to and clearance of odorants from binding sites on olfactory cilia are regulated by a complex interplay of molecular, physical and cellular factors. These perireceptor events occur primarily in the mucociliary complex. The use of gold-labelled lectinoprobes, one from Limax flavus (LFA) which is specific for terminal sialic acid residues, and one from Datura stramonium (DSA) specific for N-acetylglucosamine residues, demonstrated intricate patterns of binding in mucous domains of the olfactory mucus and ectodomains of the glycocalyx of olfactory cilia. In electron micrographs of Lowicryl-embedded salamander olfactory mucosa, the mucus consisted of an electron-dense domain that lay superficial to an electron-lucent domain; the interface between the two was irregular. A significantly higher density of binding sites for both lectins was present in the superficial than in the deeper domain. The two domains were not homogeneous: there were small electron-lucent domains (hsL) within the superficial electron-dense domain (hsD) that bound a 4.8-fold lower density of gold-labelled DSA than the surrounding matrix, and the olfactory cilia, which project into hsD, were surrounded by an electron-lucent sheath that appeared to be continuous with the deeper domain. Ectodomains of the glycocalyx associated with olfactory cilia exhibited a higher density of binding sites for both LFA and DSA than did either microvilli of sustentacular cells or respiratory cilia. Specificity of the lectinoprobes was confirmed by inhibition of binding with specific sugars or enzymic removal of specific sugar residues. These results demonstrated microchemical heterogeneity of the non-homogeneous mucous domains in olfactory mucus and in the attendant glycocalyx of olfactory cilia based on the differential localization of sialic acid and N-acetylglucosamine sugar residues.
气味剂从嗅觉纤毛上的结合位点的获取和清除受到分子、物理和细胞因素复杂的相互作用的调节。这些受体周围事件主要发生在黏液纤毛复合体中。使用金标记的凝集素探针，一种来自黄蛞蝓（LFA），对末端唾液酸残基具有特异性，另一种来自曼陀罗（DSA），对N - 乙酰葡糖胺残基具有特异性，结果显示在嗅觉黏液的黏液区域和嗅觉纤毛糖萼的胞外区域存在复杂的结合模式。在Lowicryl包埋的蝾螈嗅觉黏膜的电子显微照片中，黏液由一个电子致密区域和一个电子透明区域组成，电子致密区域位于电子透明区域的表面；两者之间的界面不规则。两种凝集素的结合位点在表面区域的密度明显高于深层区域。这两个区域并非均匀一致：在表面电子致密区域（hsD）内存在小的电子透明区域（hsL），其结合的金标记DSA的密度比周围基质低4.8倍，伸入hsD的嗅觉纤毛被一个似乎与深层区域连续的电子透明鞘所包围。与嗅觉纤毛相关的糖萼的胞外区域显示出比支持细胞的微绒毛或呼吸道纤毛更高的LFA和DSA结合位点密度。通过用特定糖类抑制结合或酶促去除特定糖残基证实了凝集素探针的特异性。这些结果基于唾液酸和N - 乙酰葡糖胺糖残基的差异定位，证明了嗅觉黏液和嗅觉纤毛伴随的糖萼中不均匀黏液区域的微化学异质性。
