Ultrastructural demonstration of phosphatases by perfusion fixation followed by perfusion incubation of rat liver.

An alternative to previous methods (tissue chopper, frozen sections) for the ultrastructural demonstration of phosphatases is described. The present approach is based on a short vascular perfusion of rat liver with glutaraldehyde through the inferior caval vein, followed by vascular perfusion incubation with a medium containing the enzyme substrates. The effect of glutaraldehyde on three different types of phosphatases was investigated, namely a lysosomal enzyme (acid phosphatase) a tightly bound microsomal enzyme (G6Pase) and a loosely bound microsomal enzyme (IDPase). It is demonstrated that by perfusion with glutaraldehyde for three minutes good cellular morphology is obtained and that 50-60% of the initial activity of glucose-6-phosphatase, inosine-diphosphatase and acid phosphatase remains. The localization and deposition of G6Pase activity were distinct and observed throughout the endoplasmic reticulum and the nuclear envelope. For acid phosphatase, the reaction product was confined to various types of lysosomes including presumed autophagic vacuoles. No signs of enzyme diffusion were noted. The present approach seems to offer some advantages: it is simple and requires no extra equipment, penetration of the fixative and incubation enzyme medium is good, and finally freeze artifacts are avoided.