REDISTRIBUTION OF CARBONIC-ANHYDRASE-VI EXPRESSION FROM DUCTS TO ACINI DURING DEVELOPMENT OF OVINE PAROTID AND SUBMANDIBULAR GLANDS

Carbonic anhydrase VI (CA VI) is a secreted enzyme produced predominan tly by serous acinar cells of submandibular and parotid glands. We hav e investigated the developmental pattern of CA VI production by these glands in the sheep, from fetal life to adulthood, using immunohistoch emistry. Also, a specific radioimmunoassay for CA VI was used to measu re changes in enzyme expression in the parotid gland postnatally. CA V I is detectable by immunohistochemistry in parotid excretory ducts fro m 106 days gestation (term is 145 days), in striated ducts from 138 da ys and in acinar cells from 1 day postnatal. The duct cell content of CA VI declined as the acinar cell population increased, a feature also of CA VI immunoreactivity in the submandibular gland. Production of C A VI by submandibular duct cells was detectable initially at 125 days gestation, and acinar production was not seen before 29 days post-nata l. Apart from the differing ontogeny of CA VI production in ducts and acini of parotid and submandibular glands, there was a parallel patter n of CA VI expression during the development of these major salivary g lands. With the development of the acinar tissues in the postnatal. la mb, there was a dramatic increase (about 600-fold) in the level of exp ression of CA VI in the parotid gland between days 7 and 59 as measure d by radioimmunoassay.