Diastaseinsensitive

Diastaseinsensitive is an adjective used in histology and pathology to describe substances or structures that are not digested by diastase, an enzyme (typically alpha-amylase) that hydrolyzes glycogen and other starch-like carbohydrates. The term is most often encountered in the context of PAS staining and diastase digestion protocols.

In routine histochemical practice, tissue sections are sometimes treated with diastase before applying the periodic acid–Schiff (PAS) reaction. Glycogen, a diastase-sensitive substance, is removed by this digestion and subsequently fails to stain with PAS. Substances that remain PAS-positive after diastase treatment are called diastase-resistant or diastase-insensitive. This distinction helps differentiate glycogen from other carbohydrate-containing components in tissue.

Examples of diastase-insensitive PAS-positive material commonly cited include certain mucopolysaccharides and glycoproteins, such as some mucins and proteoglycans, as well as particular basement membrane components. The identification of diastase-insensitive material can aid in the characterization of tissue composition and in differential diagnosis in surgical pathology.

Beyond histology, the general idea of diastase insensitivity can refer to any substance that is not digested by diastase enzymes. However, the term is predominantly used within histochemical contexts to contrast with diastase-sensitive glycogen.