Effect of monensin on secretion of basement membrane collagen by cultured rabbit corneal endothelial cells in comparison with rabbit tendon fibroblasts.

Monensin, a monovalent ionophore, affects differently the secretion of basement membrane collagen and interstitial procollagen. At 1 X 10(-8) M, monensin inhibited only slightly the secretion of procollagen synthesized by tendon cells while secretion of basement membrane collagen synthesized by endothelial cells was inhibited by 43% after 2 hours of labelling. At higher concentration (1 X 10(-6) M), the secretion of type I procollagen by tendon cells was inhibited after two h (36%) or 24 h (24%) of labelling. The pattern of basement membrane collagen secretion varied from inhibition to stimulation depending on the labeling time. No changes in the phenotypic expression of collagen were observed in either the monensin-treated tendon cultures or endothelial cells. Phase-contrast microscopy revealed differential responses of cells to monensin: tendon cells appeared spindle-shaped or rounded-up, in contrast to the enlarged shape displayed by endothelial cells.