Effect of plant cytokinins on microfilaments and tight junction permeability

Abstract

IN epithelia classified as “leaky”, net transport efficiency of NaCl and water may be determined not only by cellular metabolic activity, but also by tight junction permeability and the conjugate physical driving forces acting between lumen and intercellular space. The significance of paracellular ion movement across leaky epithelia would become more apparent if a cytoplasmic mechanism for regulation of tight junctional permeability could be defined. The structure–function observations reported here suggest that the microfilament system may have such a function. Rapid and reversible increases in shunt path electrical resistance were observed in Necturus gallbladder exposed to plant cytokinins. In electron micrographs zeiotic transformation of the luminal membrane was associated with disruption of microfilaments and in freeze fracture, with reorientation and disorder of tight junctional elements.