Kidney Flat Mount Preparation: A Procedure to Dissect and Prepare a Flat Mount for Microscopic Analysis of Adult Zebrafish Kidney

The adult zebrafish contains a single, flattened kidney attached to the dorsal body wall through connective tissues. It consists of three main regions: head, trunk, and tail. The functional unit of the kidney, nephrons, are highly branched and drain into two major collecting ducts. 

To isolate the kidney, first, prep a euthanized adult zebrafish with its ventral side facing up. Make an incision behind the operculum - a bony flap covering the gills - to remove the head. Subsequently, make another incision from the head to the base of the caudal or tail fin to expose and remove the internal organs.

Now, pin open the body walls to visualize the kidney. Dissect the underlying connective tissue to detach the kidney from the dorsal wall. Transfer the organ into a vial containing a suitable buffer, washing it thoroughly to remove debris. The buffer helps provide physiological conditions. Post wash, place the kidney, hydrated with buffer, on a glass slide.

Ensure that the kidney is completely flattened, making cuts in the connective tissue if necessary. This step aids in easy visualization during imaging. Finally, secure the organ preparation using a coverslip affixed with modeling clay pieces at its corners. The clay helps prevent tissue deformation. The flat-mounted tissue is now ready for microscopic analysis.