Zenker's fixative

Zenker's fixative is a histological fixative, used in anatomy and pathology for preserving tissues for examination. It is named after the German pathologist Friedrich Albert von Zenker who introduced it in 1894. Zenker's fixative is particularly useful for preserving the morphology of cellular components and maintaining the histochemical properties of tissues. This fixative is a modification of Helly's fixative, which is itself a modification of Müller's fluid.

Composition

Zenker's fixative contains:

• Mercuric chloride (HgCl2) - acts as the primary fixative agent.
• Potassium dichromate (K2Cr2O7) - serves as an oxidizing agent.
• Sodium sulfate (Na2SO4) - used to prevent the precipitation of mercuric chloride.
• Acetic acid - helps in the preservation of nuclear structures and cytoplasmic components.

Mechanism of Action

The fixative works by cross-linking proteins, which helps in preserving the structural integrity of tissues. Mercuric chloride is the main component responsible for the fixation process, while potassium dichromate acts as a mordant to enhance the staining properties of tissues. Acetic acid penetrates tissues rapidly and fixes nuclear proteins, preserving nuclear details and cytoplasmic structures.

Applications

Zenker's fixative is widely used in histology for the preservation of a variety of tissues, including those of the gastrointestinal tract, lymph nodes, and endocrine glands. It is particularly favored for its ability to preserve delicate structures like cilia and microvilli. However, due to its mercury content, tissues fixed with Zenker's fixative require thorough washing in running water to remove any residual mercury and prevent artifact formation during staining.

Safety and Environmental Concerns

The use of Zenker's fixative poses significant health and environmental risks due to its mercury content. Mercury is a toxic heavy metal, and its disposal must be handled with care to avoid environmental contamination. Laboratories using Zenker's fixative are advised to follow strict safety protocols and use mercury disposal methods in accordance with local regulations.

Alternatives

Due to the toxic nature of mercury, alternative fixatives have been developed, such as formalin and Davidson's fixative, which offer similar preservation qualities without the associated health and environmental risks.

See Also

• Histology
• Fixative (histology)
• Friedrich Albert von Zenker
• Mercuric chloride
• Potassium dichromate