Histological study of the intercalated cells of the rat cortical collecting ducts in response to an acute potassium bicarbonate load

Background:The renal collecting duct (CD) is responsible for the final tuning of electrolyte and acid–base homeostasis. It is lined by principal cells (PCs) and intercalated cells (ICCs). There are two subtypes of ICCs. Type A-ICCs predominate in the medullary CD and are responsible for hydrogen secretion. Type B-ICCs predominate in the cortical CD and are responsible for bicarbonate secretion. Aim of the work :To detect the histological changes in the cortical CD in response to an acute potassium bicarbonate (KHCO3) load. Materials and methods:Ten adult albino rats were equally divided into two groups. The control group received 2 ml tap water at 5, 3, and 1 h before anesthesia. The treated group received 2 ml 0.5 mmol KHCO3. Specimens from the renal cortex were prepared for both light microscopic (LM) and electron microscopic (EM) studies. Staining of LM sections was by H E, and iron hematoxylin for mitochondria. A morphometric study was carried out by counting ICCs/cortical CD. Results:The epithelium of the cortical CD of the treated group became columnar with predominant ICCs. Most ICCs became binucleated and showed apical cytoplasmic blebbing. With iron hematoxylin, there was an increase in the positively stained cells. EM study indicated that most ICCs were type-B. They showed a large number of mitochondria, a reduction in the apical tubulovesicles, and the appearance of extended chromatin with obvious nucleosomes in their nuclei. Morphometry indicated that there was a highly significant increase in the number of cortical ICCs. Conclusion:There was an increase in both the number and the activity of type-B ICCs in response to an acute KHCO3 load.