Increased size of stage II and III melanosomes during PUVA therapy

Abstract

Four different theories have been presented to show how early melanosomes are formed and at what stage in melanosome formation melanization starts. In the present investigation the perikaryon of melanocytes have been studied and the longitudinal and the transverse diameter of stage I-IV melanosomes estimated before and after PUVA therapy in 5 patients. An increase in the longitudinal diameter of stage II and III melanosomes was found, whereas no increase in stage I and IV melanosomes was detected. No increase in vesiculo-globular bodies was detected in stage I and II melanosomes after PUVA therapy, while in stage III melanosomes vesiculo-globular bodies appeared to have increased in number of PUVA therapy. It is concluded that during stimulated melanogenesis--as seen after PUVA therapy--an unknown mechanism is activated, causing increased amounts of structural proteins to be incorporated into each stage II melanosome. The vesiculo-globular bodies do not appear to take part in this process.