Atypical flagellar structure associated with endocrine cells of rat pituitary

Atypical flagellar structures containing eight subfibers arrayed around a single, central element (8 + 1) are associated with pituitary secretory cells, largely gonadotropes. Less frequently, flagella with a 7 + 2 pattern are seen. Both types appear commonly in pituitary tissues obtained from both male and female rats above 1 year of age and appear to penetrate the cells. Except for the pattern of the array, the structures are similar in dimension to commonly observed flagellar structures (9 + 2) when viewed in sections cut either in perpendicular or sagittal to the major axis. The (8 + 1) flagella are observed both singly and in pairs. Steroidal milieu (ovariectomy with or without steroid replacement) does not seem to influence their appearance. Flagella with the common 9 + 2 arrangement are not observed in the rat pituitary.