HEAT-SHOCK PROTEINS HSP25, HSP60, HSP72, HSP73 IN ISOOSMOTIC CORTEX AND HYPEROSMOTIC MEDULLA OF RAT-KIDNEY

The distribution of heat shock proteins (HSP) HSP60, HSP73, HSP72 and HSP25 in the isoosmotic cortex and the hyperosmotic medulla of the rat kidney was investigated using Western blot analysis and immunohistoch emistry. HSP73 was homogeneously distributed throughout the whole kidn ey. The level of HSP60 was high in the renal cortex and low in the med ulla. HSP25 and HSP72 were present in large amounts in the medulla. On ly low levels of HSP25 and almost undetectable amounts of HSP72 were f ound in the cortex. HSP25 exists in one nonphosphorylated and several phosphorylated isoforms. Western blot analysis preceded by isoelectric focussing showed that HSP25 predominates in its nonphosphorylated for m in the outer medulla but in its phosphorylated form in cortex and in ner medulla. Although this intrarenal distribution pattern was not cha nged during prolonged anaesthesia (thiobutabarbital sodium), a shift f rom the nonphosphorylated to the phosphorylated isoforms of HSP25 occu rred in the medulla. The characteristic intrarenal distribution of the constitutively expressed HSPs (HSP73, HSP60, HSP25) may reflect diffe rent states of metabolic activity in the isoosmotic (cortex) and hyper osmotic (medulla) zones of the kidney. The high content of inducible H SP72 in the medulla most likely is a consequence of the osmotic stress imposed upon the cells by the high urea and salt concentrations in th e hyperosmotic medullary environment.