CYTOCHEMICAL AND PHYSICAL PROPERTIES OF MYOFIBER EXTERNAL LAMINA

The structure and staining characteristics of isolated rat muscle sarcolemmal tubes were examined in the optical and electron microscopes with and without prior staining with ruthenium red. The sarcolemmal tubes, which chiefly consisted of a layer of external lamina with a few collagen microfilaments embedded in the surface and segments of cell membrane, were little affected by incubation with neuraminidase, hyaluronidase and collagenase. However, approximately 50% of the external lamina (EL) was extracted by 0.1-0.3 M lithium diiodosalicylate. Dialysis of the lithium diiodosalicylate extract yielded a fluffy, poorly soluble, thixotropic, acidic (pK 9.9) gel (external lamina substance) which had staining properties similar to the EL in tissue sections. External lamina substance has properties consistent with an acidic glycoprotein or proteoglycan.