Internal absorption coefficient and threshold for pulsed laser disruption of melanosomes isolated from retinal pigment epithelium

This study determine the threshold radiant exposure from a 10-ns pulsed laser (532 nm) which caused bovine melanosomes to present various observable endpoints of disruption. The endpoints tested were (1) a visible region of clearing in a uniform field of melanosomes under a glass cover slip, (2) an audible sound, and (3) the increase in melanin photoreactivity due to photodisruption of melanosomes. The thresholds were tested for different starting temperatures by pre-equilibrating the melanosomes in aqueous solution at various temperatures. Lower temperatures required larger exposures to attain a given endpoint. The data suggest that bovine RPE melanosomes are about 4-fold denser in melanin content than cutaneous melanosomes.