ABSTRACT
Melatonin is a lipophilic hormone that causes a broad spectrum of metabolic andphysiological effects in the central nervous system and peripheral organs. It hasbeen described that the hormone modulates kidney physiology, since modifies urine production and osmolarity in rats. MDCK cells are derived from a canine kidney that in culture form functional monolayers similar to the natural epitheliums. These cells form tight junctions and transport water that accumulate between the basolateral domain and the solid surface of the petri dishes forming blisters or domes. Both tight junction sealing and dome formation depend on microfilament rearrangements. It has been shown that melatonin causes cytoskeletal reorganization in cultured cells through both calmodulin and protein kinase C interactions. Current evidence indicates that cytoskeletal organization participates in structural polarity and cell shape maintenance, as well as in a broad spectrum of cell functions. In this paper we will review the recent evidence on the melatonin effects on microfilament organization in the kidney derived epithelial MDCK cells that occur concomitant with an increase in water transport in culture conditions that resembles the cyclic changes of melatonin plasma circulating levels. It is proposed that the hormone may synchronize renal cell physiology with the photoperiod through cyclic cytoskeletal reorganization. Also, the participation of PKC in the mechanism by which melatonin causes a cyclic increased water transport and microfilament reorganization is discussed.
