IMMUNOLOCALIZATION OF NEUROPHYSIN IN CYTOKERATIN-POSITIVE LUTEAL CELLS OF COWS

We have recently detected a subgroup of cytokeratin (CK)-positive lute al cells in the bovine corpus luteum of the early and mid-luteal phase , but not in that of pregnancy. Since, according to the literature, ne urophysin (NP)-positive luteal cells behave comparably, simple immunoh istochemistry and double labeling were used to identify in serial sect ions whether the presence of NP coincided with that of CK. The numbers of CK-positive cells and NP-positive luteal cells were comparable thr oughout the estrous cycle, decreasing from early to late luteal phase. While few CK-positive cells were found in the for mer thecal layer du ring the early luteal phase, many CK-positive cells appeared in the fo rmer granulosal layer. NP-positive cells were only detected in the for mer granulosal layer. During the mid-luteal phase, the CK-positive cel ls consisted of small and large luteal cells, but only large NP-positi ve cells were found. Roughly 80% of the large CK-positive cells contai ned NP, whereas CK was lacking in more than 50% of the NP-positive cel ls. The corpora lutea of pregnancy contained neither CK-positive nor N P-positive cells. The significance of the simultaneous occurrence of C K and NP remains to be elucidated.