Effects of retinol on follicular porcine thyrocytes in culture

Retinoids influence proliferation and differentiation in transformed thyroi d cell lines. Retinoids are able to damage cells by destabilizing lysosomal membranes and induce apoptosis in certain cell lines. In normal thyrocytes retinol modulates iodine metabolism. At concentrations higher than 50x10(- 6) M retinoids are cytotoxic for normal (not transformed) thyroid cells. Th e mechanism of this cytotoxicity is unknown. We studied the effect of 7-80x 10(-6) M retinol on porcine follicular thyrocytes in culture. In order to d ifferentiate between membrane-destabilizing effects and apoptosis we invest igated cultures after incubation with retinol by light- and electron-micros copy and by labeling of potential nicks in the DNA helix by terminal deoxyn ucleotidyltransferase-dUTP mediated DNA nick end labeling. We conclude that the observed cytotoxicity is caused mainly by the induction of apoptosis.