Retinoic acid modulates dome formation by MDCK cells in defined medium.
Retinoic acid dramatically increases the size of domes in confluent MDCK monolayers in a hormonally defined medium (medium K-1). After 4-5 days of retinoic acid treatment, enlarged domes began to appear in confluent MDCK monolayers. After 7 days with 3 x 10(-7) M retinoic acid, the majority of the domes in the monolayers were between 27 and 80 x 10(-3) microns 2 in area, whereas in control medium the majority of the domes were between 0 and 9 x 10(-3) microns 2 in area. The dependence of the retinoic acid effect on prostaglandin E1 (PGE1) was examined. In normal MDCK cells, the effects of retinoic acid on dome size were observed only in medium K-1 supplemented with PGE1. This observation indicated that retinoic acid did not elicit its effects simply by stimulating PGE production. In contrast, in monolayers of PGE1-independent MDCK cells, retinoic acid treatment resulted in an increase in dome frequency even in medium K-1 lacking PGE1. This observation can be explained by the elevated cyclic adenosine monophosphate (cAMP) levels in these PGE1-independent MDCK cells. Dibutyryl cAMP-resistant MDCK cells, which normally do not form domes in medium K-1, were also studied. Remarkably, the dibutyryl cAMP-resistant MDCK cells were observed to form domes at a significant frequency when medium K-1 was supplemented with retinoic acid. However in medium K-1 lacking PGE1, an effect of retinoic acid on dome formation by dibutyryl cAMP-resistant MDCK monolayers was not observed. The inability of dibutyryl cAMP-resistant MDCK cells to form domes in medium K-1 has previously been attributed to their decreased cAMP-dependent protein kinase activity. The stimulatory effects of retinoic acid on dome formation may possibly be due to an increase in the activity of a particular cAMP-dependent protein kinase or activation of a separate pathway.
Taub
M
M
Biochemistry Department, State University of New York, Buffalo 14214.
D000527:Alprostadil / Q000494:pharmacology*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D003470:Culture Media; D004285:Dogs; D004847:Epithelial Cells; D007668:Kidney / Q000166:cytology; D014212:Tretinoin / Q000494:pharmacology*
D003470:Culture Media; D014212:Tretinoin; D003994:Bucladesine; D000527:Alprostadil