Enzyme histochemical localization of Na+,K+‐ATPase and NADH‐DE in the developing rat parotid gland

Information on ductal differentiation in the developing rat parotid gland is sparse. Striated and excretory ducts are rich in a number of enzymes related to ion movement. The objective of this investigation was to delineate histochemically the chronology of two of these, ouabain‐sensitive Na+,K+‐ATPase and NADH‐DE, in the developing rat parotid gland. Parotid glands were excised from rats at representative ages from 20 days in utero to 42 days. Enzyme histochemistry was performed on air‐dried frozen sections. For Na+,K+‐ATPase, some sections also were fixed in phosphate‐buffered formalin. Ouabain blocked Na+,K+‐ATPase activity, and neither enzyme reacted without substrate. Weak Na+,K+‐ATPase reactions were initially seen in unfixed sections at 1 day, and increased steadily to the adult pattern of strong (concentrated basolaterally) in striated ducts and excretory ducts, respectively, and weak to modest (diffuse) in acini and intercalated ducts at 28 days. In fixed sections, localization was sharper but the reaction was somewhat reduced. NADH‐DE was modest in terminal buds and ducts before birth, then progressively changed to the adult pattern of weak in acini and intercalated ducts and strong (concentrated basally and luminally) in striated and excretory ducts at 28 days. As demonstrated by enzyme histochemistry of Na+,K+‐ATPase and NADH‐DE, differentiation of rat parotid striated ducts and excretory ducts occurs mainly between birth and 28 days. Anat Rec 256:72–77, 1999. Published 1999 Wiley‐Liss, Inc.